Equipment for performing polarization-resolved Raman spectroscopy

Abstract

A device for performing polarization-resolved Raman spectroscopy on a sample (11), in particular a single-crystal or polycrystalline sample, the device comprising: at least one light source (13, 87, 93, 95, 97), in particular at least one laser, for providing excitation radiation to a surface of the sample (11); an optical system configured to simultaneously collect at least one on-axis Raman beam (21, 109) and at least one off-axis Raman beam (23, 111) from Raman light scattered by the sample (11) in response to exposing the surface to the excitation radiation, the at least one on-axis Raman beam (21, 109) being scattered from the sample (11) in a direction aligned with an optical axis of an objective lens (41) of the optical system for collecting the at least one on-axis Raman beam (21, 109), The at least one off-axis Raman beam is scattered from the sample in a direction tilted relative to an optical axis of an objective lens (41) of an optical system for collecting the at least one off-axis Raman beam (23, 111), the optical system comprising at least one polarizer device (25, 113) for generating at least one polarized on-axis Raman beam (31, 33) from the at least one on-axis Raman beam (21, 109) and at least one polarized off-axis Raman beam (35) from the at least one off-axis Raman beam (23, 111), and the optical system comprising at least one spectrometer (37, 47, 81, 83, 85) for generating a spectrum from each of the at least one polarized on-axis Raman beam (31, 33) and the at least one polarized off-axis Raman beam (35), in particular simultaneously.

Description

[0001] European Patent Application No. 19213599.4 from which this application claims priority, and European Patent Application No. 19213597.8 from which the disclosures of both documents are incorporated herein by reference.

[0002] The present invention relates to an apparatus and a method for performing polarization-resolved Raman spectroscopy on a sample, in particular a single-crystal or polycrystalline sample.

[0003] Spectroscopy generally refers to the process of measuring the energy or intensity of a beam of light as it changes with its wavelength. Spectroscopy allows for the qualitative and quantitative study of physical properties and processes by physical matter, particularly atoms, molecules, or ions, through the absorption, emission, or scattering of light.

[0004] Light or radiation directed toward the sample during operation of the spectrometer system may be referred to as incident radiation. The redirection of the incident radiation upon contact with the sample is often referred to as scattering of the radiation. If, instead of reflecting the incident radiation, atoms or molecules in the sample absorb all or part of the incident radiation, the sample may be excited and the energy level of the sample may increase to a higher energy level. The light may be scattered but may continue to have the same wavelength as the incident radiation, a situation often referred to as Rayleigh or elastically scattered light. Incident radiation scattered by the sample during, for example, a change in the vibrational state of a molecule may be scattered at different energies, and this scattered light may be referred to as Raman scattered light. These phenomena have been used in conjunction with spectroscopy to qualitatively and quantitatively study physical properties and processes, including identifying the chemical nature, composition, and structure of a sample.

[0005] If the incident radiation is directed toward the sample, the wavelength of the incident radiation can remain essentially unchanged in the scattered radiation. Alternatively, if the incident radiation is directed toward the sample, the wavelength of the scattered radiation can acquire one or more wavelengths different from the incident wavelength. The energy difference between the incident and scattered radiation can be referred to as the Raman shift. Spectroscopic measurement of Raman scattered light can seek to measure the resulting wavelength of this scattered light.

[0006] The phenomenon of Raman scattered light is extremely useful in spectroscopy applications for the qualitative and quantitative study of physical properties and processes, including identifying the chemical properties, composition, and structure of samples. Raman shift spectroscopy is used for both qualitative and quantitative investigations of samples. If incident radiation is used to scatter light from a sample and the scattered radiation is measured, the scattered radiation provides one or more frequencies associated with the sample, along with the intensities of those shifted frequencies. These frequencies can be used to identify the sample's chemical composition.

[0007] Raman spectrometers are an example of spectrometers used to measure inelastic scattered light, and they are often used to obtain Raman spectra of samples. When a sample is illuminated with monochromatic light, such as by a laser, the light scattered by the sample will contain wavelength components that differ from those present in the incident light. This effect is often caused by so-called Raman scattering of light by molecules present in the sample. In a Raman spectrometer, the light scattered by the sample is collected, and the spectral distribution of wavelength components with wavelengths different from that of the light source is detected (e.g., in the form of a digital image).

[0008] In some Raman spectroscopy measurements, it may be necessary to obtain information about the polarization of the Raman scattered light. For example, the polarization-dependent properties of Raman scattering depend on the single-crystalline quality and crystallographic orientation of the substrate, which consists of, for example, a single-crystalline silicon (Si) wafer. Ramabhadra et al. describe in a scientific publication, "Intensity Analysis of Polarized Raman Spectroscopy of Off-Axis Single-Crystal Silicon," Materials Science and Engineering B 230, pp. 31-42, 2018, that polarized backscattered Raman spectroscopy can be used to identify the crystallographic orientation of the silicon cutoff axis.

[0009] Muñisau et al. proposed in the scientific publication "Raman tensor analysis of sapphire single crystals and its application to defining the crystal orientation in polycrystalline alumina", Solid State Physics B 246, No. 8, 1893-1900 (2009), a tensor algorithm for practical determination of unknown crystal structures in polycrystalline alumina materials.

[0010] WO 03 / 089890 A1 discloses an imaging spectrometer comprising a polarizing beam splitter, such as a Wollaston prism.

[0011] It is an object of the present invention to provide an efficient means for performing polarization-resolved spectroscopy on samples, in particular single-crystal or polycrystalline samples.

[0012] This object is achieved by a device according to the features of claim 1. Preferred embodiments of the invention are described in the dependent claims.

[0013] An apparatus for performing polarization-resolved Raman spectroscopy on a sample, in particular a single-crystal or polycrystalline sample, comprises: at least one light source, in particular at least one laser, for providing excitation radiation to the surface of the sample;

[0014] an optical system configured to collect at least one off-axis Raman beam from Raman light scattered by the sample in response to exposing the surface of the sample to excitation radiation,

[0015] at least one off-axis Raman beam is scattered from the sample in a direction tilted relative to an optical axis of an objective lens, the objective lens being configured to collect the at least one off-axis Raman beam,

[0016] wherein the optical system further comprises at least one polarizer device for generating at least one polarized off-axis Raman beam from the collected at least one off-axis Raman beam, and

[0017] The optical system further comprises at least one spectrometer for generating a spectrum from at least one polarized off-axis Raman beam.

[0018] In some embodiments, the optical system is configured to simultaneously collect at least one on-axis Raman beam in addition to at least one off-axis Raman beam, wherein the at least one on-axis Raman beam is scattered from the sample in a direction aligned with an optical axis of an objective lens of the optical system, the objective lens being configured to collect the at least one on-axis Raman beam. Furthermore, the at least one polarizer device is configured to generate at least one polarized on-axis Raman beam from the at least one on-axis Raman beam. Furthermore, the at least one spectrometer is configured to generate a spectrum from each of the at least one polarized on-axis Raman beam and the at least one polarized off-axis Raman beam, in particular simultaneously.

[0019] In at least some embodiments, an apparatus for performing polarization-resolved Raman spectroscopy on a sample, particularly a single crystal or polycrystalline sample, includes:

[0020] at least one light source, in particular at least one laser, for providing excitation radiation to the surface of the sample;

[0021] an optical system configured to simultaneously collect at least one on-axis Raman beam and at least one off-axis beam from Raman light scattered by the sample in response to exposing the surface to excitation radiation;

[0022] the at least one coaxial Raman beam being scattered from the sample in a direction aligned with an optical axis of an objective lens of the optical system for collecting the at least one coaxial Raman beam,

[0023] the at least one off-axis Raman beam being scattered from the sample in a direction tilted relative to an optical axis of an objective lens of the optical system for collecting the at least one on-axis Raman beam,

[0024] The optical system comprises at least one polarizer device for generating at least one polarized on-axis Raman beam from at least one on-axis Raman beam and at least one polarized off-axis Raman beam from at least one off-axis Raman beam, and

[0025] The optical system includes at least one spectrometer for generating a spectrum from each of the at least one polarized on-axis Raman beam and the at least one polarized off-axis Raman beam.

[0026] The spectra obtained from the optionally polarized on-axis Raman beam and the off-axis Raman beam can be used to perform two-dimensional (2D) or three-dimensional (3D) non-destructive orientation mapping of the surface (2D) or volume (3D) of the sample. In particular, if the sample is a single crystal or polycrystalline sample, orientation mapping of the grains can be performed. Polycrystalline materials are composed of multiple grains (also called crystallites).

[0027] Instead of obtaining one or more polarized on-axis Raman beams from a collected on-axis Raman beam, some embodiments may utilize one or more polarized off-axis Raman beams obtained by collecting only off-axis Raman beams. In some embodiments, off-axis Raman beams and / or on-axis Raman beams may be collected simultaneously, and spectra of at least some of the corresponding polarized on-axis and / or off-axis Raman beams may be detected simultaneously.

[0028] Orientation mapping can provide spatially resolved information about the position, size, morphology, and crystal orientation of each grain in a polycrystalline sample, and can also provide information about the topological connectivity between grains, with a diffraction-limited spatial resolution of approximately 200 nanometers. Therefore, the apparatus according to the present invention can also be used to obtain crystallographic information about a sample. In 3D orientation mapping, the volume thickness is very small due to the short penetration depth of light into the sample.

[0029] In theory, if the symmetry group of the crystal is known, the Raman tensor for the crystal modes can be obtained, and the intensity of the Raman signal can be simulated as a function of the sample rotation angle. The correlation between the theoretical and experimental angular intensity dependence can be used to determine the local crystal orientation. Until now, polarized Raman experiments have been performed by rotating the sample or by rotating a set of wave plates in the incident laser or scattered beam in the Raman setup.

[0030] However, the device according to the present invention allows polarized Raman spectroscopy, simultaneously registering the Raman spectra from at least one polarized on-axis Raman beam and at least one polarized off-axis Raman beam, or only from the polarized off-axis Raman beam, which allows avoiding ambiguities in determining the crystal orientation (e.g. by appropriate Euler angle parameterization) without changing the orientation of the sample. Therefore, there is no need to rotate the sample.

[0031] The device according to the present invention can be used in particular for simultaneous registration of multiple Raman scattering spectra acquired at different polarizations and for unambiguous orientation determination data analysis, allowing for 2D and 3D quantitative orientation mapping of polycrystalline materials. Submicron resolution, rapid data acquisition, and orientation determination with high angular accuracy and precision can be achieved.

[0032] The optical system can be configured to simultaneously collect at least one on-axis Raman beam and at least one off-axis Raman beam from Raman light scattered by the sample in response to exposing the surface to excitation radiation. The sample scatters light without any preferred directionality. Therefore, when the Raman beams are collected, for example, using an objective lens of the device, the on-axis and off-axis beams may not yet be separated from each other. The collected light can be passed through, for example, a mask having pinholes that separate the at least one off-axis beam from the at least one on-axis beam. The mask can, for example, include a plate having at least two pinholes. One pinhole can be aligned with the optical axis of the optical system, while the other pinhole is offset from the optical axis in a radial direction relative to the optical axis.

[0033] At least one light source can provide one or more laser beams to the sample. The laser beams may be polarized on their way to the sample.

[0034] In some embodiments, the at least one off-axis Raman beam travels at least a certain distance in the optical system along a propagation direction in the optical system that is radially offset from an optical axis, in particular a central optical axis of the polarizer arrangement. The central optical axis is in particular an optical axis defined by a central polarization-sensitive element, which may be a Wollaston prism.

[0035] The off-axis Raman beam can be directed through an optical element that acts on the off-axis Raman beam such that the off-axis Raman beam travels off-axis relative to the optical axis of the optical system, particularly the central optical axis of a polarizer device. For example, a polarization analyzer can be positioned off-axis relative to the optical axis, and the off-axis Raman beam can be directed through the polarization analyzer. The polarization analyzer can filter out components of the off-axis Raman beam with a specific polarization while blocking components with an orthogonal polarization.

[0036] For at least a portion of the travel distance of the off-axis Raman beam, the propagation direction of the off-axis Raman beam can be parallel to an optical axis, such as a central optical axis of the polarizer arrangement. The off-axis Raman beam and the on-axis Raman beam can travel parallel to each other for at least a portion of the travel distance. This may be particularly true for the travel distance through the polarizer arrangement.

[0037] The optical axis of the optical system can correspond to the optical axis of the objective lens used to collect the Raman light. If more than one objective lens is used to collect the Raman light, the optical axis of the optical system can be defined by the optical axis of the first objective lens used to collect the at least one coaxial Raman light beam. This optical axis can extend through the optical system, and the optical axis of the objective lens can be considered the optical axis of the optical system.

[0038] While the optical axis of the objective is considered the optical axis of the optical system, this optical axis can bend, so the optical axis is not necessarily a straight line running through the optical system. Furthermore, the optical axis can be considered the axis along which the optical components of the optical system are aligned. Furthermore, the optical components can be centered relative to the optical axis.

[0039] The optical system may include an objective lens for collecting both at least one on-axis Raman beam and at least one off-axis Raman beam. The objective lens may be aligned relative to the optical axis. The objective lens may also define the optical axis of the optical system. Other components of the optical system, in particular other components of the optical system for processing the Raman beam, may be aligned relative to the optical axis as defined by the objective lens. The use of a single objective lens allows a compact optical system to be set up for collecting Raman beams. The objective lens preferably includes a high numerical aperture (NA) to be able to collect at least one off-axis Raman beam, which beam originates from Raman light scattered from the sample at a large angle (e.g., 45°) relative to the optical axis.

[0040] The optical system may include a first objective lens for collecting at least one on-axis Raman beam and a second objective lens for collecting at least one off-axis Raman beam. Using a separate second objective lens for collecting at least one off-axis Raman beam provides the advantage that the off-axis Raman beam can be obtained from Raman light scattered from the sample at large angles. For example, the second objective lens can be arranged so that Raman light leaving the sample at angles of up to approximately 90° relative to the optical axis of the optical system can be collected. The optical axis of the optical system is preferably defined by the first objective lens.

[0041] The optical system, and in particular the polarizer arrangement, may comprise a central polarization-sensitive element, including a central polarization beam splitter and / or analyzer, in particular a Wollaston prism. The optical axis of the central polarization-sensitive element may coincide with the optical axis of the optical system. Thus, the optical axis of the central polarization-sensitive element may be aligned with the optical axis of the optical system. The central polarization-sensitive element may thus be centered relative to the optical axis.

[0042] The central polarization beam splitter can be arranged such that at least one coaxial Raman beam passes through the central polarization beam splitter, which splits the coaxial Raman beam into two polarized coaxial Raman beams, each coaxial Raman beam having a defined polarization. Thus, the central polarization-sensitive element can act on the at least one coaxial Raman beam. For example, the Wollaston prism of the central polarization-sensitive element can generate two coaxial Raman beams of orthogonal polarization for each collected coaxial Raman beam.

[0043] The optical system and in particular the polarizer arrangement may comprise at least one peripheral polarization-sensitive element, comprising a peripheral polarization beam splitter and / or analyzer, in particular a Wollaston prism, and the optical axis of the peripheral polarization-sensitive element may be arranged in a radial direction at a distance from and parallel to the optical axis of the optical system.

[0044] In some embodiments, the peripheral polarization beam splitter can be arranged such that at least one off-axis Raman beam passes through the peripheral polarization beam splitter, which splits the off-axis Raman beam into two polarized off-axis Raman beams, each off-axis Raman beam having a defined polarization.

[0045] In some embodiments, the polarization analyzer of the peripheral polarization-sensitive element can generate a polarized, preferably linearly polarized, off-axis Raman beam for each off-axis Raman beam.

[0046] The optical system may include at least one mask. The mask may include a plate placed in the path of the Raman beam. The plate may provide a pinhole for each Raman beam, in particular for each of the on-axis Raman beam and the off-axis Raman beam.

[0047] The spectrometer may include an optical diffraction grating for separating each polarized Raman beam, in particular each polarized on-axis Raman beam and each polarized off-axis Raman beam, into a spectrum having spatially separated wavelength components. The spectrometer may include a focusing lens system for directing at least a portion of each spectrum to a detector, in particular a two-dimensional array detector, such as a two-dimensional CCD detector.

[0048] The grating may be a transmission grating.

[0049] In some embodiments, the polarizer device, in particular the central polarization-sensitive element and / or the peripheral polarization-sensitive element, is arranged in a spectrometer of the optical system, in particular between an optical diffraction grating and a collimating lens system of the spectrometer. The collimating lens system can ensure that the on-axis Raman beam and the off-axis Raman beam pass through the central polarization-sensitive element and the peripheral polarization-sensitive element, respectively, as collimated beams.

[0050] In some embodiments, the polarizer arrangement, in particular the central polarization-sensitive element and / or the peripheral polarization-sensitive element, can be arranged between the objective lens of the optical system and the entrance slit of the spectrometer. Thus, the central polarization-sensitive element and / or the peripheral polarization-sensitive element can be arranged before the spectrometer.

[0051] The laser beam delivery optical system can be configured to provide polarized laser beams, preferably three laser beams, to the sample. The laser beams can be generated using at least one laser. Preferably, each laser provides laser light having a defined wavelength.

[0052] Preferably, a single laser is used for 2D orientation mapping. The laser provides light of a defined wavelength, such as 785 nanometers. Preferably, the laser emits light with a wavelength in the blue, green, or red range. As an example, the laser may emit green light at 532 nanometers.

[0053] The laser beam delivery optical system may include optical elements for generating three laser beams from laser light provided by a single laser, each laser beam having a defined polarization. Preferably, the three laser beams have different polarizations. The laser beam delivery optical system may also include optical elements for directing the polarized laser beams toward the sample.

[0054] Preferably, the three laser beams are focused to spatially separated points on the surface of the sample.Preferably, the laser beams are focused on the sample using an objective lens that collects at least one on-axis Raman beam and / or at least one off-axis beam.

[0055] With the three laser beams focused on the sample surface, three coaxial Raman beams and three off-axis Raman beams can be collected, each of which originates from one of the three incident laser beams. For example, six polarized coaxial Raman beams are generated by using a Wollaston prism to split each of the three coaxial Raman beams into two orthogonally polarized coaxial Raman beams. Therefore, six Raman spectra from the six polarized coaxial Raman beams can be detected. In addition, three polarized off-axis Raman beams are generated using, for example, a polarization analyzer for generating a polarized off-axis Raman beam from each of the three off-axis Raman beams. Therefore, three Raman spectra from the three polarized off-axis Raman beams can be detected. Therefore, the described example configuration provides six coaxial channels and three off-axis channels for detecting Raman spectra.

[0056] Preferably, three lasers are used to perform 3D orientation mapping, providing laser light of different wavelengths, for example, a first laser providing laser light of 781 nanometers, a second laser providing laser light of 783 nanometers, and a third laser providing laser light of 785 nanometers.

[0057] The laser beam delivery optical system may include optical elements for generating three laser beams from laser light provided by three lasers, each laser beam having a defined polarization. Preferably, the three laser beams have different polarizations. The laser beam delivery optical system may also include optical elements for directing the polarized laser beams toward the sample.

[0058] Preferably, the three laser beams are focused to points on the surface of the sample that can overlap spatially. Due to the wavelength differences of the incident laser beams, the detected Raman spectra can be locally separated from each spectrum on the detector array.

[0059] Preferably, an objective lens collecting at least one on-axis Raman beam and / or at least one off-axis beam is used for focusing the laser beam on the sample.

[0060] The detected Raman spectrum (particularly the intensity as a function of wavelength and polarization) can be employed for orientation mapping.

[0061] The apparatus may include a scanning stage for holding the sample. The stage may be movable in a plane perpendicular to the optical axis of the optical system. This plane may be considered the xy plane. The scanning stage may be configured to move the sample so as to avoid sample rotation. Thus, the sample does not rotate during the Raman measurement. The scanning stage allows for raster scanning of the sample's surface.

[0062] The scanning stage can also be movable in a direction parallel to the optical axis of the optical system. Thus, the scanning stage can be movable in the z-direction perpendicular to the xy plane. This can be advantageous for focusing and volume scanning.

[0063] The present invention also relates to an arrangement, in particular a polarizer arrangement, preferably for use in a device according to the invention, comprising:

[0064] a central polarization-sensitive element, which comprises a central polarization beam splitter and / or analyzer, in particular a Wollaston prism;

[0065] at least one peripheral polarization-sensitive element, comprising a peripheral polarization beam splitter and / or analyzer, in particular a Wollaston prism; and

[0066] The optical axis of the peripheral polarization-sensitive element is spaced apart from the optical axis of the central polarization-sensitive element in a radial direction and is arranged parallel to the optical axis of the central polarization-sensitive element.

[0067] In particular, in some embodiments, the central polarization-sensitive element is configured to generate two linearly polarized light beams from an incident light beam, the two linearly polarized light beams having a first polarization direction and a second polarization direction, for example, 0° and 90°, and

[0068] The at least one peripheral polarization-sensitive element is configured to generate two linearly polarized light beams from an incident light beam, the two linearly polarized light beams having a third polarization direction and a fourth polarization direction, for example 45° and 135°.

[0069] In some embodiments, a given number of peripheral polarization-sensitive elements, for example four peripheral polarization-sensitive elements, are arranged in a circumferential direction around the central polarization-sensitive element. The arrangement of the peripheral polarization-sensitive elements may be centered relative to the optical axis of the central polarization-sensitive element.

[0070] The intensity of the detected Raman spectrum depends on the polarization of the light incident on the sample, the polarization of the Raman scattered light, and the Raman tensor associated with the crystal structure under study. In addition, the Euler rotation matrix and its inverse matrix can be used to convert the crystal coordinates into the coordinates of the laboratory coordinate system. A series of equations for the crystal structure under study can be obtained, and these equations fully describe the angular dependence of the Raman mode intensity. The use of the Raman spectrum obtained from the coaxial and off-axis beams or only from the off-axis beam as provided by the device according to the present invention avoids the ambiguity in determining the Euler angles, which are three angles used to describe the crystallographic orientation of the crystal coordinate system relative to a fixed coordinate system (such as the laboratory coordinate system or the sample coordinate system), especially the orientation of the crystal plane relative to the sample surface. These Euler angles can be obtained by theoretical calculation and by experiment from the above-mentioned series of equations for known crystal structures. The nine coaxial and off-axis detection channels of the device according to the present invention as described herein allow, for example, an accuracy of about 1° to detect the Euler angles. The detection channel can be related to the signal from a polarized coaxial or off-axis beam as provided by the detector of the spectrometer.

[0071] In some embodiments of the method according to the present invention, an orientation estimation can be performed. Thus, the Euler angles associated with the orientation of the crystal planes of the sample can be estimated. The estimated Euler angles can be used together with the Raman tensor associated with the crystal structure of the sample to calculate the expected on-axis Raman beam and off-axis Raman beam intensities, or to calculate only the off-axis Raman beam intensity. The calculated intensities, in particular the on-axis and off-axis intensities, can be compared with the corresponding measured Raman beam intensities, in particular the on-axis Raman beam and the off-axis Raman beam intensities, which are obtained from the Raman spectrum measured using the apparatus according to the present invention.

[0072] At least in some experimental measurements, there may be situations where the absolute intensity is unknown. For example, the detector used to simultaneously measure the Raman spectrum may not be calibrated, so that the absolute intensity at each wavelength cannot be determined.

[0073] In some embodiments of the method according to the invention, the measured intensities of the on-axis and off-axis light beams are normalized, preferably by using at least one normalization factor.

[0074] In addition, the Euler angles associated with the orientation of the surface plane of the sample can be estimated. The estimated Euler angles can be used together with the Raman tensor associated with the crystal structure of the sample to calculate the expected on-axis Raman beam and off-axis Raman beam intensities. The calculated on-axis and off-axis intensities are preferably also normalized by using at least one normalization factor.

[0075] In some embodiments, each channel is divided by the Euclidean norm obtained from all channel intensities. A channel corresponds to one polarized on-axis or off-axis Raman beam providing a signal on the detector. Preferably, from each spectrum and therefore for each channel, a peak intensity value can be selected, and this peak intensity value can be the "intensity" obtained for that channel. The Euclidean norm of the vector consisting of the intensities of all measured channels will be equal to one. After this normalization, the relative intensity of each channel is effectively being processed, rather than the absolute intensity. This normalization is done independently in each point of the scanning grating. Other norms besides the Euclidean can be used. In some embodiments, the same normalization is applied to a selected group of channels (rather than all channels).

[0076] The calculated and then normalized intensities (particularly on-axis and off-axis intensities) are also referred to herein as normalized calculated on-axis and off-axis intensities and can be compared with the corresponding normalized intensities (particularly on-axis Raman beam and off-axis Raman beam intensities). The difference between the calculated intensities (particularly on-axis and off-axis intensities) and the measured intensities (particularly on-axis and off-axis intensities) can optionally be used to determine a correction value, which can be used to correct the estimated Euler angles. Optionally, the described process can be repeated with the corrected estimated Euler angles until the difference between the normalized calculated intensities (particularly on-axis and off-axis intensities) and the normalized measured intensities (particularly on-axis and off-axis intensities) is zero or at least close to zero to obtain the Euler angles describing the orientation of the sample surface of the sample.

[0077] In some embodiments, the detected on-axis and off-axis beams can be grouped into several groups, where each group has similar intensity in the detected Raman spectrum.

[0078] The calculated on-axis and off-axis intensities can be grouped accordingly. Corresponding normalization can be applied to the intensities of each group so as to obtain normalized intensities in each group for the calculated on-axis and off-axis intensities and the measured on-axis and off-axis intensities. The difference between the normalized calculated on-axis and off-axis intensities and the normalized measured on-axis and off-axis intensities can optionally be used to determine a correction value that can be used to correct the estimated Euler angles.

[0079] Furthermore, optionally, the described process can be repeated with the corrected estimated Euler angles until the difference between the normalized calculated on-axis and off-axis intensities and the normalized measured on-axis and off-axis intensities is zero or at least close to zero in order to obtain Euler angles that describe the orientation of the sample surface of the sample.

[0080] In some embodiments of the methods according to the present invention, a channel intensity correction factor is determined for each set of measurement channels, where each channel corresponds to a detected spectrum from a polarized on-axis or off-axis Raman beam. The set of channel intensity correction factors is then applied to the measured intensities of the Raman spectra of the set to obtain a set of corrected measured intensities of the Raman spectra. Based on these results, an orientation fit is performed, such as described above, to obtain a 2D or 3D orientation map of the sample.

[0081] Furthermore, based on Raman tensor theory, and in particular by taking into account the sample's crystal structure, the intensity of the Raman spectrum in each group can be calculated. Furthermore, by taking into account the intensity of the measured Raman spectrum for each group, the calculated intensity of the Raman spectrum for each group can be used to obtain a normalization factor. The normalization factor can be combined or averaged, taking into account the measured and calculated data for the entire scan area and, therefore, the entire mapping area.

[0082] The averaged normalization factor can be used as input for determining the channel intensity correction coefficient for each group.The corrected measured intensities of the Raman spectra can be used to obtain more accurate group-specific normalization factors.

[0083] The present invention also relates to a method for determining Euler angles of a point on a sample, the method comprising:

[0084] Provides estimated Euler angles;

[0085] providing at least one measured on-axis intensity and at least one measured off-axis intensity obtained from polarized Raman spectroscopy performed at a point on the sample, in particular by using a device according to the invention;

[0086] preferably calculating at least one on-axis intensity and at least one off-axis intensity by using a Raman tensor associated with the crystal structure of the sample;

[0087] calculating a correction value for the estimated Euler angles based on the at least one measured on-axis intensity, the at least one measured off-axis intensity, the at least one calculated on-axis intensity, and the at least one calculated off-axis intensity; and

[0088] Corrected Euler angles are determined based on the estimated Euler angles and the correction value.

[0089] In some embodiments, the calibration may be repeated until the difference between the corresponding measured and calculated values ​​is below a predetermined threshold or zero.

[0090] In some embodiments, the method may include:

[0091] (1) applying normalization to at least one measured on-axis intensity and at least one measured off-axis intensity, thereby determining at least one normalized measured on-axis intensity and at least one normalized measured off-axis intensity;

[0092] (2) applying normalization to the at least one calculated on-axis intensity and the at least one calculated off-axis intensity, thereby determining at least one normalized calculated on-axis intensity and at least one normalized calculated off-axis intensity; and

[0093] (3) Calculating correction values ​​for the estimated Euler angles based on the at least one normalized measured on-axis intensity, the at least one normalized measured off-axis intensity, the at least one normalized calculated on-axis intensity, and the at least one normalized calculated off-axis intensity.

[0094] Preferably, at least the above steps (2) and (3) may be performed repeatedly.

[0095] In some embodiments, a plurality of measured on-axis intensities and a plurality of off-axis intensities are provided, and wherein the measured on-axis intensities are grouped into at least one group, wherein the measured off-axis intensities are grouped into at least one group, wherein group-specific normalization is applied to the intensities of the associated group.

[0096] The present invention also relates to a method for determining Euler angles for a plurality of points on a sample, the method comprising:

[0097] calculating a plurality of intensities of the points for a predetermined set of detection channels, wherein preferably the intensities are calculated by using a Raman tensor;

[0098] providing the set of detection channels with a plurality of measured intensities for the points, wherein the measured intensities are preferably obtained by using a device according to the present invention;

[0099] calculating at least one correction factor for correcting the measured intensity based on the calculated plurality of intensities;

[0100] applying at least one correction factor to the measured intensities, thereby obtaining corrected measured intensities for the set of detection channels for the points; and

[0101] Based on the corrected measured intensities of the set of detection channels, the Euler angles of these points are calculated.

[0102] The calculated intensity can represent a calculated value for the intensity that can be obtained using the apparatus according to the present invention when performing a polarized Raman scattering experiment at a point on a sample. For each point on the sample, a Raman spectrum can be obtained using the apparatus according to the present invention for both a polarized on-axis Raman beam and an off-axis Raman beam, or only a polarized off-axis Raman beam. Each resulting spectrum can be associated with a detection channel of the apparatus, and a number of detection channels selected from the detection channels that can be provided by the apparatus can be considered a set of detection channels.

[0103] For each point, at least one intensity for each detection channel of a predetermined set of detection channels is measured and / or calculated.

[0104] The predicted or calculated intensities and the corresponding measured intensities can be used to calculate one or more correction coefficients, which can be used to obtain corrected intensities. These intensities can also be further used to determine the Euler angles of a point on the sample.

[0105] In some embodiments, the method further comprises at least one of the following:

[0106] Determine the orientation map of the points based on the calculated Euler angles;

[0107] applying normalization to the calculated plurality of intensities to obtain a normalized calculated plurality of intensities, the normalized calculated plurality of intensities being used in place of the calculated plurality of intensities for calculating at least one correction factor;

[0108] Using multiple measured intensities was used to determine normalization;

[0109] At least one correction factor is calculated, the correction factor comprising determining at least one correction factor for each point and averaging over all points.

[0110] The orientation map can be a graphical representation showing the Euler angles at all points, for example, by using color coding. The measured on-axis intensity can be an intensity value, particularly a peak value, taken from the Raman spectral data obtained from the on-axis Raman beam. The measured off-axis intensity can be an intensity value, particularly a peak value, taken from the Raman spectral data obtained from the off-axis Raman beam. The calculated intensity can be the corresponding intensity value.

[0111] The steps of the above method can be performed repeatedly.

[0112] The above method, or at least some of the steps, may be performed by a computer, preferably a computer linked to an apparatus as described herein.

[0113] The invention also relates to a data processing system comprising means for performing at least some of the steps of the method as described herein.

[0114] The invention also relates to a computer program product comprising instructions which, when executed by a computer, cause the computer to perform the steps of the method as described herein.

[0115] The invention also relates to a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to perform the steps of the method as described herein.

[0116] More than one exemplary embodiment of the present invention will be described below with reference to the following drawings, in which like reference numerals represent like elements:

[0117] Figure 1 a shows a flow chart illustrating steps that may be used in conjunction with an apparatus for performing polarization-resolved Raman spectroscopy;

[0118] Figure 1 b schematically shows the working principle of an exemplary embodiment of an apparatus for performing polarization-resolved Raman spectroscopy according to the present invention;

[0119] Figure 2 schematically shows an optical setup of an exemplary embodiment of a device according to the invention;

[0120] Figure 3 Schematically shows Figure 2 A perspective view of a detector of the device;

[0121] Figure 4 schematically shows a perspective view of an exemplary embodiment of a device according to the present invention;

[0122] Figure 5 AF schematically illustrates the design and operating principle of an exemplary embodiment of the device according to the present invention;

[0123] Figure 6 shows a cross-sectional view of an optical device having a central polarization-sensitive element and four peripheral polarization-sensitive elements;

[0124] Figure 7 A diagram schematically illustrating a fitting method for finding the orientation angle is shown;

[0125] Figure 8 shows a diagram schematically illustrating another fitting method for finding an orientation angle that can compensate for the unknown absolute intensity of a detected Raman beam; and

[0126] Figure 9 A diagram schematically illustrating the process of calibrating channel intensities is shown.

[0127] Polarization-resolved Raman spectroscopy can be used for spectroscopic analysis of samples. In particular, for single crystal or polycrystalline samples, polarization-resolved Raman spectroscopy can be used for orientation mapping.

[0128] The grains of a polycrystalline sample often have different crystallographic orientations. A complete three-dimensional (3D) orientation map of the grains can provide information about the position, size, morphology, and orientation of each grain, as well as about the topological connectivity between grains. Such a map can help link structure to properties.

[0129] Based on experimental and theoretical studies on quantitative orientation mapping using Raman spectroscopy, a method and apparatus have been developed that are particularly suitable for performing polarization-resolved Raman spectroscopy on single-crystalline or polycrystalline samples. This method is also known as SAROM.

[0130] like Figure 1 As shown in , such development is included in step 1001 of the design and construction of an exemplary embodiment of an apparatus for performing polarization-resolved Raman spectroscopy, which may also be referred to as a polarizing (confocal) Raman microscope.

[0131] As will be explained later, the apparatus allows for the acquisition of a detected Raman beam from a sample. From each detected Raman spectrum, a spectrum can be obtained. Step 1003 involves preprocessing the obtained spectrum and performing artifact correction. Artifact correction can include correction for at least one of: wavelength-dependent intensity attenuation, Raman intensity scaling and normalization, linear phase (LP) and linear amplitude (LA) anisotropy of each optical element, and depth-dependent birefringence.

[0132] As shown in step 1005, linear phase and linear amplitude compensation can be performed with respect to a laser beam delivery system (LBDS) and with respect to a Raman beam delivery system (RBDS). The laser beam delivery system can be an optical system for providing one or more laser beams to the sample, each laser beam preferably having a defined polarization. The Raman beam delivery system can be considered an optical device configured to process Raman light scattered by the sample.

[0133] As shown in steps 1007 and 1009, correction or compensation may be applied with respect to the numerical aperture (NA) of the objective lens used to focus the laser beam from the LBDS on the sample and / or collect Raman light scattered from the sample.

[0134] As shown in step 1009 , artifact correction may also include correction and merging of spectral BG modes.

[0135] According to step 1011, the flow chart includes Raman tensor analysis of the sample crystal structure. If the symmetry of the crystal is known, the Raman tensor for the crystal mode can be obtained, and the relationship between the Raman intensity and the sample position angle can be simulated. The calibration between the theoretical and experimental angular intensity correlations can be used to determine the local crystal orientation.

[0136] Alternatively, the relationship between the Raman intensity and the sample rotation angle can be determined experimentally by performing one or more rotation measurements on a single crystal sample as shown in step 1013. This can be used to verify the functionality of an apparatus or method according to the present invention, where rotation of the sample is not required.

[0137] Optionally, in step 1015 , a fit to simulated or experimental data is performed to verify the Raman tensor model. This step can be used if the symmetry of the sample is unknown.

[0138] In step 1017 , the polycrystalline sample is scanned while collecting Raman signals using an apparatus for performing polarization-resolved Raman spectroscopy.

[0139] Based on the collected Raman signals, a 2D or 3D map of the surface of the scanned sample may be generated according to step 1019 in a color-coded representation.

[0140] An embodiment of an apparatus for performing polarization-resolved Raman spectroscopy according to the present invention will be described in more detail below.

[0141] Figure 1 FIG. b schematically shows the working principle of an exemplary embodiment of an apparatus according to the present invention for performing polarization-resolved Raman spectroscopy on a sample 11. The sample 11 is in particular a single crystal or a polycrystalline sample.

[0142] The apparatus includes at least one light source 13 configured to provide three laser beams 15, 17, and 19 having different polarization orientations. For example, laser beam 15 has a polarization of 0°, laser beam 17 has a polarization of 45°, and laser beam 19 has a polarization of 90°. The three laser beams 15, 17, and 19 are focused on the sample 11, preferably at spatially separated points. This configuration is particularly useful in 2D mapping configurations.

[0143] The apparatus further comprises an optical system having an optical axis (A). The optical axis A may be defined by an objective lens of the optical system for collecting Raman light scattered from the sample 11. The optical components of the optical system may be centered relative to and arranged along the optical axis A (see, for example, Figure 2 ).

[0144] The optical system is particularly configured to collect at least one on-axis Raman beam 21 and at least one off-axis Raman beam 23 of Raman light scattered from the sample in response to exposing the sample 11 to excitation radiation provided by the three laser beams 15 to 19. The optical system of the apparatus also includes a Wollaston analyzer unit (WAU) 25, which includes a central polarizing beam splitter 27 and an analyzer 29. The optical axis of the central polarizing beam splitter 27 coincides with the optical axis A of the optical system. Each of the three on-axis Raman beams is split into two perpendicularly polarized beams 31, 33, for example, having 0° and 90° polarizations.

[0145] The analyzer 29 is located at a distance in a radial direction relative to the optical axis A. The optical axis of the analyzer 29 may be aligned such that it is parallel to the optical axis A of the optical system.

[0146] In addition, the analyzer 29 is positioned so that the three off-axis Raman beams 23 pass through the analyzer 29, which is configured to filter, for example, a 90° polarization component from each of the three off-axis Raman beams 23, thereby generating three polarized off-axis Raman beams 35. A total of six polarized off-axis Raman beams 31, 33 and three polarized off-axis Raman beams 35 are further sent through a spectrometer that includes a transmission grating that separates each polarized Raman beam 31 to 35 into its spectral components. This produces nine different spectra with spatially separated wavelength components, which are detected by using a focusing lens system (CCD for charge coupled device) on different areas on a two-dimensional CCD array detector 39. Figure 1 The detector 39 may also be a CMOS detector or any other suitable type of detector. CMOS is the acronym for Complementary Metal Oxide Semiconductor. Figure 1 The device of b allows for the simultaneous registration of nine Raman spectra obtained from the collected on-axis Raman beam and off-axis Raman beams, where each Raman spectrum has a specific polarization.

[0147] The device can be used in raster scanning mode. In particular, it can be used to measure surface points on sample 11. Sample 11 and / or the points of laser beams 15 to 19 on its surface can then be moved to measure other surface points. This allows the surface of sample 11 to be scanned, and measurement values ​​can be obtained from multiple surface points. The measured data can be used to map the sample's surface.

[0148] Figure 1 The setting of b is particularly useful for 2D orientation mapping and can therefore be used to obtain information about the position, size, morphology and orientation of one or more surface planes of the sample 11.

[0149] according to Figure 1 The device of b is particularly advantageous because it allows simultaneous collection of the on-axis Raman beams 31, 33 and the off-axis Raman beam 23 from Raman light scattered by the sample 11, and processing the on-axis Raman beam 21 and the off-axis Raman beam 23 independently of each other in the optical system.

[0150] In particular, in order to process the on-axis Raman beam and the off-axis Raman beam independently of each other, the optical system comprises at least one optical device, here a Wollaston analyzer unit WAU 25, which is configured to generate at least one polarized on-axis Raman beam 31, 33 and at least one polarized off-axis Raman beam 35 from each of the on-axis Raman beam 21 and the off-axis Raman beam 23. From at least one selection of these polarized Raman beams, a spectrum can be obtained using a detector 39.

[0151] Figure 2The optical setup of an exemplary embodiment of the device according to the invention is schematically shown. Figure 2 The laser beam delivery optical system, not shown, is also referred to herein as a laser beam delivery system (LBDS), which is configured to provide a polarized laser beam to the sample 11 (e.g., see Figure 1 When the sample 11 is irradiated with the polarized Raman laser beam, the Raman light can be scattered by the sample.

[0152] The optical system includes an objective lens 41 that is aligned with the optical axis A of the optical system and is used to collect a portion of the Raman light that can be received by the objective lens 41 in response to exposing the sample 11 to the laser beam from the Raman light scattered by the sample. The objective lens 41 can be a customized objective lens, and the objective lens 41 can have a large diameter and / or a high numerical aperture. The objective lens 41 can be an immersion objective lens that allows off-axis measurements to be performed at 45° relative to the optical axis A. Due to the objective lens 41 and an optional mask with pinholes, at least one on-axis Raman beam and at least one off-axis Raman beam can be obtained, wherein one pinhole is aligned with the optical axis A and the other pinhole is located radially outside the optical axis A. In some embodiments, only one or more off-axis Raman beams are collected. Therefore, a pinhole aligned with the optical axis A is not required.

[0153] The focusing lens 41 focuses the at least one on-axis Raman beam and the at least one off-axis Raman beam into a spectrometer 47 through a slit 45 . The spectrometer includes a collimating lens 49 for collimating the at least one on-axis Raman beam and the at least one off-axis Raman beam.

[0154] The spectrometer 47 further comprises one, two or even more filters 51 after the Wollaston analyzer unit 25. The unit 25 may comprise a central polarizing beam splitter (not shown) having an optical axis aligned with the optical axis A of the optical system. The polarizing beam splitter can generate two orthogonally polarized coaxial Raman beams from the coaxial Raman beam. Each of these polarized Raman beams has a specific polarization, and these beams are locally separated from each other and travel in different directions.

[0155] The unit 25 also comprises a peripheral analyser (not shown) which acts as a polarisation filter to remove polarisations other than those of the off-axis Raman beam that passes through the analyser.After the analyser, the off-axis Raman beam is polarised with the polarisation set by the analyser.

[0156] The polarized on-axis Raman beam and the polarized off-axis Raman beam pass through a transmission diffraction grating 53 that separates each beam into its spectral components. The spectral components are focused onto a detector 39 using a focusing lens system 55, which can simultaneously detect the spectra from the polarized on-axis Raman beam and the polarized off-axis Raman beam in different areas of the detector 39.

[0157] Figure 3 A perspective view is shown of a detector 39 which may be a CCD array detector. Figure 3 Represents the detection of different spectra 57 obtained from coaxial or off-axis beams of different polarizations on different areas of the detector 39. Theoretical studies of orientation ambiguity and errors have shown that basic orientation determination becomes possible for four or more channels, where each channel is associated with one detected spectrum. For certain specific orientations, the intensity data remains ambiguous and the rotation angle of the sample surface cannot be recovered. For example, this is the case with the (111) crystal plane of a silicon dioxide wafer, where the misorientation angle can vary from zero to the maximum possible for a cubic symmetric structure corresponding to 62.8 degrees. However, even for such ambiguous data, some orientation data can be recovered, and even with four measurement channels, the silicon dioxide wafer crystal planes (100) and (111) can be clearly distinguished. Determining the complete wafer orientation typically requires determining nine or more channels.

[0158] In a 2D mapping configuration, the sample 11 is preferably illuminated with a single laser source. Three laser beams with different polarization orientations are spatially separated on the sample 11 and on the spectral CCD focal plane. The three laser beams with three different polarization orientations generate six polarized on-axis Raman beams and three polarized off-axis Raman beams.

[0159] In a 3D mapping configuration, sample 11 is preferably illuminated using three different laser sources. The three generated laser beams have different wavelengths and polarization orientations. Their points may completely or partially overlap on the surface of sample 11. Due to the slightly different excitation wavelengths, they appear separated in the plane of detector 39.

[0160] Figure 4 A perspective view of a further exemplary embodiment of the device according to the invention is schematically shown. In this embodiment, the sample 11 is placed on a scanning stage 57. The scanning stage 57 can be moved in a plane perpendicular to the optical axis of the optical system of the device.

[0161] The apparatus includes two lasers 59 and 61. Lasers 59 and 61 can be used, for example, selectively. The first laser 59 can provide laser light with a wavelength of 532 nanometers. The second laser can provide laser light with a wavelength of 785 nanometers. A polarizer 63 is used to polarize the laser beam provided by the first laser 59, so that a polarized laser beam 67 can be provided by the first laser 59 toward the sample 11. The polarized laser beam 67 is reflected from the mirror 69 and from the dichroic mirror 71, which reflects the laser beam 67 so that it travels along the optical axis A. In addition, the beam 67 is focused by the objective lens 41, which is also used to collect Raman scattered light from the sample 11.

[0162] Similarly, polarizer 65 is used to polarize laser light provided by second laser 61, thereby providing polarized laser beam 73 to sample 11. Laser beam 73 is reflected from mirror 75 and dichroic mirror 71, so that laser beam 73 also travels along optical axis A and through objective lens 41 to the sample.

[0163] The laser beams 67, 73 may pass through a dichroic mirror 77. The dichroic mirror 77 is used to reflect the laser beam provided by the microscope 79 so that the laser beam from the microscope also travels along the optical axis A toward the sample 11.

[0164] The setup of the optical system for processing the Raman light scattered from the sample 11 can be similar to that described with respect to Figure 1 b and Figure 2 Describe the optical system.

[0165] As a specific example, Figure 4 The apparatus shown in FIG. 8 includes a first spectrometer 81 for detecting spectra of a polarized on-axis Raman beam and a polarized off-axis Raman beam obtained from a 785 nm laser beam provided by a second laser 61 .

[0166] The second spectrometer 83 is a low-resolution spectrometer for resolving the Raman spectra of the polarized on-axis and off-axis beams obtained from the 532 nm laser light provided by the first laser 59. The third spectrometer 85 is a high-resolution spectrometer that can also be used in conjunction with the first laser 59.

[0167] Figure 5 a shows the optical setup of the device according to the present invention. The function of the device is similar to that of detecting Raman light from a sample 11 as compared to Figure 1 b. Figure 2 and Figure 3 However, unlike Figure 2 Compared with the embodiment of Figure 5 In the device shown in , the Wollaston analyser cell 25 is located between the objective lens 41 and the entrance slit 45 of the spectrometer 47 .

[0168] As previously described, in order to perform 2D quantitative orientation mapping relative to the sample, it is preferably only one laser 87 is used. As an example, the laser 87 can provide a laser with a wavelength of 785 nanometers. The laser beam 89 provided by the laser 87 is divided into three parts and is therefore divided into laser beams 89a, 89b and 89c. Each of the laser beams 89a, 89b and 89c is polarized with a different polarization (e.g., 0°, 45° and 90°). Therefore, one of the beams has a polarization of 0°, one of the beams has a polarization of 45°, and one of the beams has a polarization of 90°. The laser beams 89a, 89b and 89c are superimposed again and reflected from the dichroic mirror 91 so that the laser beams 89a, 89b and 89c travel along the optical axis A toward the sample 11. They are preferably focused on spatially separated points on the sample by the objective lens 41. Figure 5 The left panel of e shows a microscope image of three laser spots on sample 11.

[0169] In order to perform 3D orientation mapping, three lasers 93, 95 and 97 are preferably used. For example, laser 93 can provide a laser beam with a wavelength of 781 nanometers and can be linearly polarized at a polarization angle of 0°. Laser 95 can provide a laser beam with a wavelength of 783 nanometers and can be linearly polarized at a polarization angle of 45°. Laser 97 can provide a laser beam with a wavelength of 785 nanometers and can be linearly polarized at a polarization angle of 90°. Laser beams 99a, 99b and 99c can be superimposed and delivered to sample 11. Preferably, three laser beams with different polarization state orientations overlap on sample 11. Correspondingly, Figure 5 The right side of e shows only one laser point 101 in the microscope image.

[0170] The Raman beams detected at detector 39 become separated due to slightly different excitation wavelengths. Figure 5 f shows images of the resulting Raman spectra from the drug carbamazepine obtained on the detector in 2D configuration (left-hand image) and 3D configuration (right-hand image).

[0171] also, Figure 5 b shows in the upper part an image of a polarized Raman spectrum through the slit 45 of the spectrometer 47 for a 2D configuration. Figure 5 The bottom image in b shows the polarized Raman beam passing through the spectral slit focal plane for the 3D configuration.

[0172] Figure 5 FIG. 3 c shows a coaxial Raman beam 109 passing through the Wollaston prism 103 arranged in the unit 25 . Thus, two coaxial Raman beams of perpendicular polarization are generated. Each of the two polarized coaxial beams generates a Raman spectrum in a different region of the detector 39 .

[0173] also, Figure 5 Figure c shows an off-axis Raman beam 111 passing through the analyzer 105 arranged in the unit 25. Thus, a linearly polarized off-axis Raman beam is generated. The spectrum of this beam is also detected by using the detector 39.

[0174] like Figure 5 As shown in FIG. 3 c, the unit 25 may include a mask 107. The mask 107 may, for example, be in the form of a plate with pinholes (not shown) through which the on-axis Raman beam and the off-axis Raman beam can pass. These pinholes help shape the on-axis Raman beam and the off-axis Raman beam.

[0175] Figure 5 d schematically shows the Raman signal collection geometry for the sample 11 illuminated by the incident laser beam and in the on-axis (0°) and off-axis (45°) scattering paths. Figure 5 As shown in d, the off-axis Raman beam may be due to Raman scattered light that is tilted at an angle of up to 45° relative to the optical axis A of the objective lens 41.

[0176] Each polarized on-axis or off-axis Raman beam whose spectrum is detected on the detector 39 may be considered as a detection channel provided by the exemplary apparatus as described above.

[0177] Figure 6 A cross-sectional view of an optical device 113 is shown having a central polarization-sensitive element, here a central Wollaston prism 115 , and four peripheral polarization-sensitive elements, here four peripheral Wollaston prisms 117 circumferentially arranged around the central Wollaston prism 115 .

[0178] The central Wollaston prism 115 is configured to generate two polarized on-axis Raman beams (having 0° and 90° polarization) for each incident on-axis Raman beam. Each peripheral Wollaston prism 117 is also configured to generate two polarized off-axis Raman beams (having 45° and 135° polarization) for each incident off-axis Raman beam.

[0179] For example, with respect to Figure 5 In the optical setup described, the optical device 113 can be used as a replacement for the WAU 25 , wherein the optical axis of the central Wollaston prism 115 is aligned with the optical axis A.

[0180] From the incident light on the sample 11 (see Figure 5) can collect one on-axis Raman beam from each of the three beams 89a, 89b, 89c or 99a, 99b or 99c, thereby generating six polarized on-axis Raman beams emitted from the central Wollaston prism 115. In addition, from each of the three beams incident on the sample 11, an off-axis Raman beam can pass through each peripheral Wollaston prism 117. Therefore, six polarized off-axis Raman beams can be emitted from each peripheral Wollaston prism 117. This will generate 30 polarized on-axis Raman beams and off-axis Raman beams, and thus generate 30 detection channels.

[0181] Preferably, the three laser beams are not used to be incident on the sample 11 simultaneously. Instead, they are used sequentially to irradiate the sample 11. Therefore, by Figure 5 Using optical device 113 in the setup shown in , 10 channels can be detected simultaneously.

[0182] The optical device 113 may be arranged in this arrangement at a different location than the WAU 25. For example, the optical device may be positioned between the collimating lens 46 and the grating 53.

[0183] Objective lens 41 (see Figure 5 ) and a peripheral Wollaston prism 117 having an optical axis deviated from the optical axis A of the optical system can also be used to separate the off-axis Raman beam from the Raman signal provided by the objective lens 41 to the device 113. Similarly, the Wollaston prism 115 can be used to separate the on-axis Raman signal from the Raman signal. Mask 107 (see Figure 5 c) can optionally be used to spatially separate the on-axis Raman beam and the off-axis Raman beam from each other.

[0184] Figures 7 to 9 Exemplary methods are described that can be applied to perform 2D and 3D orientation mapping for a sample based on Raman intensities measured from monitoring channels.

[0185] Figure 7 A diagram schematically illustrates a first exemplary embodiment of the method according to the invention. The method involves a fitting method to find orientation angles corresponding to the Euler angles that are related to the orientation of the surface plane of the sample.

[0186] In step 601 , estimated Euler angles are provided.

[0187] In step 603, the estimated Euler angles can be used together with the theoretically known Raman tensor to determine the crystal structure of the sample.

[0188] In step 605 , the expected on-axis Raman beam and off-axis Raman beam intensities are calculated.

[0189] In step 607 , measured on-axis Raman beam and off-axis Raman beam intensities are provided.

[0190] In step 609, the calculated on-axis and off-axis intensities and the corresponding measured on-axis Raman beam and off-axis Raman beam intensities may be used to determine correction values. The correction values ​​may be used to correct the estimated Euler angles.

[0191] The process may restart from step 601 again using the corrected Euler angles as new estimated Euler angles.

[0192] This process can continue until the correction value or difference between the calculated on-axis and off-axis intensities and the measured on-axis and off-axis intensities is zero or below a predetermined threshold. The obtained Euler angles are then assumed to describe the orientation of the sample surface at the location on the sample where the measured intensities were obtained.

[0193] Still refer to Figure 7 In some embodiments, a method of determining Euler angles for a point on a sample includes:

[0194] In step 601, estimated Euler angles are provided;

[0195] In step 607 , at least one measured on-axis intensity and at least one measured off-axis intensity obtained from polarized Raman spectroscopy performed on a point of the sample, in particular by using an apparatus as described herein, is provided;

[0196] (a) in steps 603 and 605, calculating at least one on-axis intensity and at least one off-axis intensity, preferably by using a Raman tensor related to the crystal structure of the sample,

[0197] (b) in step 609, calculating a correction value for the estimated Euler angles based on the at least one measured on-axis intensity, the at least one measured off-axis intensity, the at least one calculated on-axis intensity, and the at least one calculated off-axis intensity, and

[0198] (c) Based on the estimated Euler angles and the correction values, a corrected Euler angle is determined.

[0199] Steps (a) to (c) may be repeated iteratively until the correction value and difference between the corrected Euler angles and the previous Euler angles are below a threshold or zero.

[0200] Figure 8 A diagram schematically illustrates a second exemplary embodiment of the method according to the invention. The method involves another fitting method of finding orientation angles corresponding to the Euler angles related to the orientation of the surface plane of the sample.

[0201] In step 701, the intensities measured for the on-axis beam and the off-axis beam are grouped into several groups, where each group has similar intensities in the detected Raman spectrum. Figure 8 As shown in FIG, according to step 701a, the intensities measured for the on-axis Raman beams are grouped into one group, for example, group 1. According to step 701b, the intensities measured for some of the off-axis Raman beams are grouped into another group, for example, group 2. According to step 701c, the intensities measured for the remaining off-axis Raman beams are grouped into yet another group, for example, group 3.

[0202] In step 703a, the intensity of group 1 is normalized to obtain a normalized intensity for group 1. In step 703b, the intensity of group 2 is normalized to obtain a normalized intensity for group 2. In step 703c, the intensity of group 3 is normalized to obtain a normalized intensity for group 3.

[0203] In step 705, Euler angles associated with the orientation of the surface plane of the sample are estimated.

[0204] In step 707, the estimated Euler angles are used together with the Raman tensor associated with the crystal structure of the sample to calculate the expected on-axis and off-axis Raman beam intensities for groups 1, 2, and 3 in steps 709a, 709b, 709c.

[0205] In step 711a, the on-axis intensities calculated for group 1 are normalized. In step 711b, the off-axis intensities calculated for group 2 are normalized. In step 711c, the off-axis intensities calculated for group 3 are normalized.

[0206] In step 713, for each group 1 to 3, a correction value is calculated using the calculated and measured normalized intensities.

[0207] The correction values ​​obtained in step 713 are used to determine corrected Euler angles, which are used in a new step 705. The process as described above may be repeated again, for example until the correction values ​​determined in step 713 are below a predetermined threshold.

[0208] In some embodiments, and using Figure 7 As a starting point, Figure 8 The method comprises applying normalization to at least one measured on-axis intensity and at least one measured off-axis intensity according to steps 703a, 703b, 703c, thereby determining at least one normalized measured on-axis intensity and at least one normalized measured off-axis intensity,

[0209] Normalization is applied to at least one calculated on-axis intensity and at least one calculated off-axis intensity according to steps 709a, 709b, 709c, thereby determining at least one normalized calculated on-axis intensity and at least one normalized calculated off-axis intensity, and a correction value for the estimated Euler angle is calculated based on at least one normalized measured on-axis intensity, at least one normalized measured off-axis intensity, at least one normalized calculated on-axis intensity, and at least one normalized calculated off-axis intensity according to step 713.

[0210] In addition, in some embodiments, according to steps 701a, 701b, and 701c, multiple measured on-axis intensities and multiple measured off-axis intensities are provided, and the measured on-axis intensities are grouped into at least one group, and the measured off-axis intensities are grouped into at least one group, and according to steps 703a, 703b, and 703c, group-specific normalization is applied to the intensities of the associated groups.

[0211] Figure 9 A diagram schematically illustrating the process of correcting channel intensities is shown.

[0212] In step 801 , channel intensity correction coefficients A1 , A2, A3, B1 , B2, B3 are determined for each set of measured channels A, B. Each channel A, B corresponds to a polarized on-axis or off-axis Raman beam.

[0213] In step 803 , channel intensity correction coefficients A1 , A2 , A3 , B1 , B2 , B3 are applied to the measured intensities of the Raman spectra of the associated group.

[0214] In step 805 , an orientation fit is performed, from which a 2D or 3D orientation map of the sample is obtained in step 807 .

[0215] In step 809 , from Raman tensor theory, in particular by taking into account the crystal structure of the sample, the intensities of the Raman spectra can be calculated as they are expected to appear in each group.

[0216] In step 811 , the intensity of the Raman spectrum calculated for each group is used to obtain a normalization factor in step 813 by considering the intensity of the Raman spectrum measured for each group according to step 803 .

[0217] In step 815 , the normalization factors may be combined or averaged taking into account the measured and calculated data obtained for the entire scan area and, therefore, the entire mapped area.

[0218] The average normalization factors obtained in step 815 can be used as input for determining channel intensity correction coefficients for each group.The corrected measured intensities of the Raman spectra can be used in step 801 to obtain more accurate group-specific normalization factors.

[0219] In some embodiments, a method of determining Euler angles for a plurality of points on a sample includes:

[0220] Calculating a plurality of intensities for points of a predetermined set of detection channels (steps 809 and 811), wherein the intensities are preferably calculated by using Raman tensors;

[0221] providing a plurality of measured intensities of points for the set of detection channels (step 803);

[0222] calculating at least one correction coefficient for correcting the measured intensity based on the calculated plurality of intensities (step 801);

[0223] applying at least one correction factor to the measured intensities, thereby obtaining, for the points, corrected measured intensities for the set of detection channels (steps 801 and 803);

[0224] Based on the corrected measured intensities of the set of detection channels, the Euler angles of these points are calculated (step 805).

[0225] Additionally, the method may include at least one of the following:

[0226] Based on the calculated Euler angles, determining an orientation map for the point (step 807);

[0227] applying normalization to the calculated plurality of intensities to obtain a normalized calculated plurality of intensities, the normalized calculated plurality of intensities being used to replace the calculated plurality of intensities in calculating at least one correction coefficient (step 813);

[0228] using the plurality of measured intensities for determining normalization (steps 803 and 813);

[0229] Calculating at least one correction coefficient includes determining at least one correction coefficient for each point and averaging over all points (step 815).

[0230] In relation to Figures 1 to 9 In the examples described, it is assumed that both on-axis and off-axis Raman beams are collected. However, in some embodiments, only one or more off-axis Raman beams are collected, thereby only having polarized off-axis Raman beams. The intensity of the spectrum obtained from the off-axis Raman beam can also be used in the surface mapping process.

[0231] Preferred embodiments of the invention are also described in the following lists. Features mentioned for one embodiment may also be present in another embodiment, even if this is not explicitly mentioned.

[0232] Item 1: An apparatus for performing polarization-resolved Raman spectroscopy on a sample, in particular a single crystal or polycrystalline sample, the apparatus comprising:

[0233] at least one light source, in particular at least one laser, for providing excitation radiation to the surface of the sample;

[0234] an optical system configured to simultaneously collect at least one on-axis Raman beam and at least one off-axis Raman beam from Raman light scattered by the sample in response to exposing the surface to excitation radiation;

[0235] at least one coaxial Raman beam is scattered from the sample in a direction aligned with the optical axis of the optical system,

[0236] at least one off-axis Raman beam is scattered from the sample in a direction tilted relative to the optical axis of the optical system,

[0237] The optical system is configured to generate at least one polarized on-axis Raman beam from at least one on-axis Raman beam and at least one polarized off-axis Raman beam from at least one off-axis Raman beam, and

[0238] The optical system is further configured to generate a spectrum from each of the at least one polarized on-axis Raman beam and the at least one off-axis Raman beam.

[0239] Item 2: The device described in Item 1,

[0240] It is characterized by

[0241] At least one off-axis Raman beam travels along a propagation direction offset from an optical axis in the optical system.

[0242] Item 3: Equipment according to item 1 or 2,

[0243] It is characterized by

[0244] The optical system comprises an objective lens for collecting both the at least one on-axis Raman beam and the at least one off-axis Raman beam, the objective lens being aligned with respect to the optical axis.

[0245] Item 4: Equipment according to item 1 or 2,

[0246] It is characterized by

[0247] The optical system includes a first objective lens for collecting at least one on-axis Raman beam and a second objective lens for collecting at least one off-axis Raman beam.

[0248] Item 5: A device according to any of the preceding items,

[0249] It is characterized by

[0250] The optical system comprises a central polarization-sensitive element, which comprises a central polarization beam splitter and / or analyzer, in particular a Wollaston prism, and

[0251] The optical axis of the central polarization sensitive element coincides with the optical axis of the optical system.

[0252] Item 6: A device according to any of the preceding items,

[0253] It is characterized by

[0254] The optical system comprises at least one peripheral polarization-sensitive element, comprising a peripheral polarization beam splitter and / or analyzer, in particular a Wollaston prism, and

[0255] The optical axis of the peripheral polarization-sensitive element is at a distance from the optical axis of the optical system in a radial direction and is arranged parallel to the optical axis of the optical system.

[0256] Item 7: A device according to any one of items 5 or 6,

[0257] It is characterized by

[0258] The central polarizing beam splitter is arranged such that the at least one on-axis Raman beam passes through the central polarizing beam splitter, which splits the off-axis Raman beam into two polarized off-axis Raman beams, wherein each polarized off-axis Raman beam has a defined polarization, and / or

[0259] The peripheral polarization beam splitter is arranged such that at least one off-axis Raman beam passes through the peripheral polarization beam splitter, which splits the off-axis Raman beam into two polarized off-axis Raman beams, wherein each polarized off-axis Raman beam has a defined polarization.

[0260] Item 8: A device according to any one of Items 5 or 7,

[0261] It is characterized by

[0262] The analyzer of the central polarization-sensitive element or the analyzer of the peripheral polarization-sensitive element is configured to generate a polarized on-axis Raman beam or a polarized off-axis Raman beam from the corresponding on-axis beam or off-axis beam.

[0263] Item 9: A device according to any one of the preceding items,

[0264] It is characterized by

[0265] The optical system includes at least one mask that provides a pinhole for each of the on-axis Raman beam and the off-axis Raman beam.

[0266] Item 10: A device according to any one of the preceding items,

[0267] It is characterized by

[0268] The optical system comprises a spectrometer comprising an optical diffraction grating for separating at least one polarized on-axis Raman beam and at least one polarized off-axis Raman beam into spectra having spatially separated wavelength components, and

[0269] The spectrometer further comprises a focusing lens system for directing at least a portion of each spectrum to a detector, in particular a two-dimensional array detector, such as a two-dimensional CCD detector.

[0270] Item 11: The device according to any one of items 5 to 10,

[0271] It is characterized by

[0272] The central polarization-sensitive element and / or the peripheral polarization-sensitive element are arranged in a spectrometer of the optical system, in particular between an optical diffraction grating and a collimating lens system of the spectrometer, or

[0273] The central polarization-sensitive element and / or the peripheral polarization-sensitive element are arranged between the objective lens of the optical system and the entrance slit of the spectrometer.

[0274] Item 12: A device according to any one of the preceding items,

[0275] It is characterized by

[0276] The laser beam delivery optical system is configured to provide polarized laser beams, preferably three laser beams, to the sample.

[0277] wherein these laser beams are generated by one or more lasers,

[0278] Preferably, each laser provides laser light having a defined wavelength.

[0279] Item 13: A device, in particular for use in an apparatus as described in any one of the preceding items, comprising:

[0280] a central polarization-sensitive element comprising a central polarization beam splitter and / or analyzer, in particular a Wollaston prism;

[0281] at least one peripheral polarization-sensitive element, comprising a peripheral polarization beam splitter and / or analyzer, in particular a Wollaston prism, and

[0282] The optical axis of the peripheral polarization-sensitive element is spaced apart from the optical axis of the central polarization-sensitive element in a radial direction and is arranged parallel to the optical axis of the central polarization-sensitive element.

[0283] Item 14: A method for determining the Euler angles of a point on a sample, the method comprising:

[0284] Provides estimated Euler angles,

[0285] (a) providing at least one measured on-axis intensity and at least one measured off-axis intensity obtained from polarized Raman spectroscopy of a point of the sample, in particular by using an apparatus according to any one of items 1 to 12,

[0286] (b) calculating at least one on-axis intensity and at least one off-axis intensity, preferably by using a Raman tensor related to the crystal structure of the sample,

[0287] (c) calculating a correction value for the estimated Euler angles based on at least one measured on-axis intensity, at least one measured off-axis intensity, at least one calculated on-axis intensity, and at least one calculated off-axis intensity, and

[0288] (d) determining a corrected Euler angle based on the estimated Euler angle and the correction value,

[0289] (e) wherein steps (b) to (d) are repeatedly performed.

[0290] Item 15: The method according to Item 14, further comprising

[0291] applying normalization to the at least one measured on-axis intensity and the at least one measured off-axis intensity, thereby determining at least one normalized measured on-axis intensity and at least one normalized measured off-axis intensity;

[0292] applying normalization to the at least one calculated on-axis intensity and the at least one calculated off-axis intensity, thereby determining at least one normalized calculated on-axis intensity and at least one normalized calculated off-axis intensity; and

[0293] Correction values ​​for the estimated Euler angles are calculated based on the at least one normalized measured on-axis intensity, the at least one normalized measured off-axis intensity, the at least one normalized calculated on-axis intensity, and the at least one normalized calculated off-axis intensity.

[0294] Item 16: The method according to item 14 or 15,

[0295] Wherein a plurality of measured on-axis intensities and a plurality of measured off-axis intensities are provided, and wherein the measured on-axis intensities are grouped into at least one group, wherein the measured off-axis intensities are grouped into at least one group, wherein group-specific normalization is applied to the intensities of the associated groups.

[0296] Item 17: A method for determining Euler angles at a plurality of points on a sample, the method comprising:

[0297] calculating a plurality of calculated intensities for points of a predetermined set of detection channels, wherein the intensities are preferably calculated by using a Raman tensor and preferably based on an estimated orientation map;

[0298] Providing the set of detection channels with measured intensities at a plurality of points;

[0299] calculating at least one correction factor for correcting the measured intensity based on the calculated plurality of intensities;

[0300] applying at least one correction factor to the measured intensities to obtain corrected measured intensities for the set of detection channels for the points;

[0301] Based on the corrected measured intensities of the set of detection channels, Euler angles are calculated for these points.

[0302] Item 18: The method according to Item 17, further comprising at least one of the following:

[0303] Determine the orientation map of the point based on the calculated Euler angles;

[0304] applying normalization to the calculated plurality of intensities to obtain a normalized calculated plurality of intensities, the normalized calculated plurality of intensities being used in place of the plurality of calculated intensities for calculating at least one correction factor;

[0305] The intensity of using multiple measurements was used to determine normalization;

[0306] Calculating at least one correction factor includes determining at least one correction factor for each point and averaging over all points.

[0307] Reference Number List

[0308] 11 samples

[0309] 13 Light Source

[0310] 15 Laser Beam

[0311] 17 Laser Beam

[0312] 19 Laser Beam

[0313] 21 Coaxial Raman Beam

[0314] 23 Off-Axis Raman Beam

[0315] 25 Wollaston analyzer units

[0316] 27 Center Polarization Beam Splitter

[0317] 29 Analyzer

[0318] 31 Polarized coaxial Raman beam

[0319] 33-polarized coaxial Raman beam

[0320] 35 Polarized off-axis Raman beam

[0321] 37 Spectrometer

[0322] 39 CCD array detector

[0323] 41 objective lens

[0324] 43 Focusing lens

[0325] 45 Slit

[0326] 47 Spectrometer

[0327] 49 Collimating lens

[0328] 51 filter

[0329] 53 Diffraction Grating

[0330] 55 Focusing lens system

[0331] 57 Scanning Table

[0332] 59 Laser

[0333] 61 Laser

[0334] 63 Polarizer

[0335] 65 Polarizer

[0336] 67 Laser Beam

[0337] 69 Mirror

[0338] 71 dichroic mirror

[0339] 73 Laser Beam

[0340] 75 Mirror

[0341] 77 dichroic filter

[0342] 79 Microscope

[0343] 81 First Spectrometer

[0344] 83 Second Spectrometer

[0345] 85 Third Spectrometer

[0346] 87 Laser

[0347] 89 Laser Beam

[0348] 89a Laser beam

[0349] 89b Laser beam

[0350] 89c Laser Beam

[0351] 91 dichroic filter

[0352] 93 Laser

[0353] 95 Laser

[0354] 97 Laser

[0355] 99a Laser beam

[0356] 99b laser beam

[0357] 99c laser beam

[0358] 101 points

[0359] 103 Wollaston Prism

[0360] 105 Analyzer

[0361] 107 Mask

[0362] 109 Coaxial Raman Beam

[0363] 111 Off-Axis Raman Beam

[0364] 113 Optical Device

[0365] 115 Wollaston prism

[0366] 117 Wollaston Prism

Claims

1. An apparatus for performing polarization-resolved Raman spectroscopy on a sample, the apparatus comprising: at least one light source for providing excitation radiation to the surface of the sample; an optical system comprising an objective lens and configured to collect at least one off-axis Raman beam from Raman light scattered by the sample in response to exposing the surface to the excitation radiation, the at least one off-axis Raman beam is scattered from the sample in a direction tilted with respect to an optical axis of an objective lens of the optical system for collecting the at least one off-axis Raman beam, The optical system comprises at least one polarizer arrangement for generating at least one polarized off-axis Raman beam from the at least one off-axis Raman beam, and The optical system comprises at least one spectrometer for generating a spectrum from the at least one polarized off-axis Raman beam, It is characterized by the optical system being configured to simultaneously collect at least one on-axis Raman beam in addition to the at least one off-axis Raman beam, the at least one coaxial Raman beam being scattered from the sample in a direction aligned with an optical axis of an objective lens of the optical system, the objective lens being configured to collect the at least one coaxial Raman beam, The at least one polarizer device is further configured to generate at least one polarized coaxial Raman beam from the at least one coaxial Raman beam, and The at least one spectrometer is configured to generate a spectrum from each of the at least one polarized on-axis Raman beam and the at least one polarized off-axis Raman beam.

2. The device according to claim 1, characterized in that The at least one off-axis Raman beam travels along a propagation direction in the optical system that is offset from a central optical axis of the polarizer device.

3. The device according to claim 1 or 2, It is characterized by At least one on-axis Raman beam travels along a central optical axis of the polarizer arrangement, wherein the at least one on-axis Raman beam is or can be collected in addition to the at least one off-axis Raman beam.

4. The device according to claim 1 or 2, It is characterized by the same objective lens is configured to collect both the at least one on-axis Raman beam and the at least one off-axis Raman beam, or The optical system comprises a first objective lens for collecting the at least one on-axis Raman beam and at least one second objective lens for collecting the at least one off-axis Raman beam, wherein the at least one on-axis Raman beam is scattered from the sample in a direction aligned with the optical axis of the first objective lens, and wherein the at least one polarized off-axis Raman beam is scattered from the sample in a direction tilted relative to the optical axis of the second objective lens.

5. The device according to claim 1 or 2, It is characterized by The polarizer arrangement comprises a central polarization sensitive element comprising a central polarization beam splitter and / or analyzer, and / or The polarizer arrangement comprises at least one peripheral polarization-sensitive element comprising a peripheral polarization beam splitter and / or analyzer, the optical axis of the peripheral polarization-sensitive element being arranged at a distance from and parallel to the optical axis of the central polarization-sensitive element in a radial direction.

6. The device according to claim 5, It is characterized by the central polarizing beam splitter being arranged such that the at least one coaxial Raman beam passes through the central polarizing beam splitter, the central polarizing beam splitter splitting the coaxial Raman beam into two polarized coaxial Raman beams, wherein each of these polarized coaxial Raman beams has a defined polarization, wherein the at least one coaxial Raman beam is scattered from the sample in a direction aligned with an optical axis of the objective lens of the optical system, and / or The peripheral polarization beam splitter is arranged such that the at least one off-axis Raman beam passes through the peripheral polarization beam splitter, which splits the off-axis Raman beam into two polarized off-axis Raman beams, wherein each of these polarized off-axis Raman beams has a defined polarization.

7. The device according to claim 5, It is characterized by The analyzer of the central polarization-sensitive element or the analyzer of the peripheral polarization-sensitive element is configured to generate a polarized on-axis Raman beam or an off-axis Raman beam from a corresponding on-axis beam or an off-axis beam, wherein the at least one on-axis Raman beam is scattered from the sample in a direction aligned with an optical axis of the objective lens of the optical system.

8. The device according to claim 1 or 2, It is characterized by The optical system comprises at least one mask providing a pinhole for the at least one off-axis Raman beam, and / or The spectrometer comprises an optical diffraction grating for splitting the at least one polarized off-axis Raman beam into a spectrum having spatially separated wavelength components, and The spectrometer further comprises a focusing lens system for directing at least a portion of each of the spectra to a detector.

9. The device according to claim 5, It is characterized by The polarizer device is arranged in the spectrometer of the optical system, or The polarizer device is arranged between the objective of the optical system and an entrance slit of the spectrometer.

10. The device according to claim 1 or 2, It is characterized by having a laser beam delivery optical system configured to provide a polarized laser beam to the sample, The laser beam is generated from one or more lasers.

11. The device according to claim 1, characterized in that The sample is a single crystal or a polycrystalline sample.

12. The device according to claim 1, characterized in that The light source is a laser.

13. The device according to claim 1, characterized in that The at least one spectrometer is configured to simultaneously generate a spectrum from each of the at least one polarized on-axis Raman beam and the at least one polarized off-axis Raman beam.

14. The device according to claim 5, characterized in that The central polarizing beam splitter is a Wollaston prism.

15. The device according to claim 5, characterized in that The peripheral polarizing beam splitter is a Wollaston prism.

16. The device according to claim 8, characterized in that The at least one mask provides a pinhole for at least one coaxial Raman beam.

17. The device according to claim 8, characterized in that The optical diffraction grating is used to split at least one polarized coaxial Raman beam into a spectrum having spatially separated wavelength components.

18. The device according to claim 8, characterized in that The detector is a two-dimensional array detector.

19. The device according to claim 18, characterized in that The two-dimensional array detector is a two-dimensional CCD detector.

20. The device according to claim 9, characterized in that The polarizer arrangement is a central polarization-sensitive element and / or a peripheral polarization-sensitive element of the polarizer arrangement.

21. The device according to claim 9, characterized in that The polarizer device is arranged between the collimating lens system and the optical diffraction grating of the spectrometer.

22. The device according to claim 9, characterized in that The polarizer arrangement is the central polarization-sensitive element and / or the peripheral polarization-sensitive element.

23. The apparatus according to claim 10, wherein The laser beam transmission optical system is configured to provide three laser beams to the sample.

24. The apparatus according to claim 10, wherein Each of the lasers provides laser light having a defined wavelength.

25. A polariser arrangement for use in the apparatus of any preceding claim, the polariser arrangement comprising: a central polarization-sensitive element, the central polarization-sensitive element comprising a central polarization beam splitter and / or analyzer; four peripheral polarization-sensitive elements, each of which comprises a peripheral polarization beam splitter and / or analyzer, wherein the four peripheral polarization-sensitive elements are arranged circumferentially around the central polarization-sensitive element, and The optical axis of each of the peripheral polarization-sensitive elements is radially spaced apart from the central optical axis of the central polarization-sensitive element and is arranged parallel to the central optical axis of the central polarization-sensitive element. wherein the central polarization-sensitive element is configured to generate two linearly polarized beams having a first polarization direction and a second polarization direction from an incident beam, and Each of the peripheral polarization-sensitive elements is configured to generate two linearly polarized light beams having a third polarization direction and a fourth polarization direction from an incident light beam.

26. The polarizer device according to claim 25, characterized in that The central polarizing beam splitter is a Wollaston prism.

27. The polarizer device according to claim 25, wherein The peripheral polarizing beam splitter is a Wollaston prism.

28. The polarizer device of claim 25, wherein The first polarization direction and the second polarization direction are 0° and 90°.

29. The polarizer device of claim 25, wherein The third polarization direction and the fourth polarization direction are 45° and 135°.

30. A method for determining Euler angles of a point on a sample, the method comprising: Provides estimated Euler angles, (a) providing at least one measured on-axis intensity and at least one measured off-axis intensity or at least two measured off-axis intensities obtained from polarized Raman spectroscopy at a point on the sample using an apparatus according to any one of claims 1 to 24, wherein the on-axis intensity is the intensity of a polarized coaxial Raman beam obtained from a coaxial Raman beam scattered from the sample in a direction aligned with the optical axis of an objective lens for collecting the coaxial Raman beam, And, the off-axis intensity is the intensity of a polarized off-axis Raman beam scattered from the sample in a direction tilted with respect to the optical axis of an objective lens for collecting the off-axis Raman beam, (b) calculating at least one on-axis intensity and at least one off-axis intensity or calculating at least two off-axis intensities, (c) calculating correction values ​​for the estimated Euler angles based on the measured and calculated intensities, and (d) determining a corrected Euler angle based on the estimated Euler angle and the correction value, (e) wherein steps (b) to (d) are repeated.

31. The method according to claim 30, further comprising: applying normalization to the measured intensity to thereby determine a normalized intensity; applying normalization to the calculated intensity to thereby determine a normalized calculated intensity; as well as calculating correction values ​​for the estimated Euler angles based on the normalized intensity and the calculated intensity; and / or Wherein a plurality of measured on-axis intensities and a plurality of off-axis intensities are provided, and wherein the measured on-axis intensities are grouped into at least one group, wherein the measured off-axis intensities are grouped into at least one group, wherein group-specific normalization is applied to the intensities of the associated group.

32. The method according to claim 30, wherein The apparatus simultaneously provides at least one measured on-axis intensity and at least one measured off-axis intensity or at least two measured off-axis intensities obtained from polarized Raman spectroscopy performed at a point on the sample.

33. The method according to claim 30, wherein By using a Raman tensor associated with the crystal structure of the sample, at least one on-axis intensity and at least one off-axis intensity or at least two off-axis intensities are calculated.

34. The method according to claim 30, wherein A correction value for the estimated Euler angle is calculated based on the at least one measured on-axis intensity, the at least one measured off-axis intensity, the at least one calculated on-axis intensity and the at least one calculated off-axis intensity or based on the at least two measured off-axis intensities and the at least two calculated off-axis intensities.

35. The method according to claim 31, wherein The measured intensities are the at least one measured on-axis intensity and the at least one measured off-axis intensity or the at least two measured off-axis intensities.

36. The method according to claim 31, wherein The normalized intensity is at least one normalized measured on-axis intensity and at least one normalized measured off-axis intensity or at least two normalized measured off-axis intensities.

37. The method according to claim 34, wherein The calculated intensities are the at least one calculated on-axis intensity and the at least one calculated off-axis intensity or the at least two calculated off-axis intensities.

38. The method according to claim 36, characterized in that The normalized calculated intensities are at least one normalized calculated on-axis intensity and at least one normalized calculated off-axis intensity or at least two normalized calculated off-axis intensities.

39. The method according to claim 38, characterized in that A correction value for the estimated Euler angle is calculated based on the at least one normalized measured on-axis intensity, the at least one normalized measured off-axis intensity, the at least one normalized calculated on-axis intensity and the at least one normalized calculated off-axis intensity, or based on the at least two normalized measured off-axis intensities and the at least two normalized calculated off-axis intensities.

40. A method for determining Euler angles at a plurality of points on a sample, the method comprising: calculating a plurality of calculated intensities for a predetermined set of detection channels for points on the sample; providing the set of detection channels with measured intensities at a plurality of points, wherein the set of detection channels is provided by the apparatus according to any one of claims 1 to 24; calculating at least one correction factor for correcting the measured intensity based on the calculated plurality of intensities; applying the at least one correction factor to the measured intensities to obtain corrected measured intensities for the set of detection channels for the spots; Euler angles of the point are calculated based on the corrected measured intensities of the set of detection channels.

41. The method of claim 40, further comprising at least one of the following: determining an orientation map of the point based on the calculated Euler angles; applying normalization to the calculated plurality of intensities to obtain a normalized calculated plurality of intensities, the normalized calculated plurality of intensities being used in place of the calculated plurality of intensities to calculate the at least one correction factor; Use the intensity of multiple measurements to determine normalization; Calculating the at least one correction coefficient includes determining at least one correction coefficient for each point and averaging over all points.

42. The method according to claim 40, wherein The intensity is calculated by using the Raman tensor.

43. The method according to claim 42, characterized in that The intensities are calculated based on the estimated orientation map.

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