Method and apparatus for chemical imaging atomic force microscope infrared spectroscopy

Abstract

Methods and apparatus for spectroscopy from nanoscale to millimeter scale and imaging techniques, including atomic force microscopy, infrared spectroscopy, confocal microscopy, Raman spectroscopy, and mass spectroscopy. For infrared spectroscopy, the sample is illuminated with infrared light and the resulting sample deformation is read out with a focused UV / visible beam and / or AFM tip. The combination of the two techniques provides fast and large area measurement scans using the UV / visible light and high resolution measurements using the AFM tip. The methods and apparatus also include the ability to analyze the light reflected / scattered from the sample by a Raman spectrometer for supplemental analysis by Raman spectroscopy.

Description

[0001] This application is a divisional application of application number 201780084288.7, filed on November 29, 2017, entitled "Method and Apparatus for Infrared Spectroscopy in Chemical Imaging Atomic Force Microscopy".

[0002] AFM-IR can be a useful technique for measuring and mapping the optical properties / material composition of various surfaces with near-nanometer resolution. Various aspects of this technique are described in U.S. Patents 8,869,602, 8,680,457, 8,402,819, 8001,830, 9,134,341, 8,646,319, 8,242,448 and U.S. Patent Application 13,135,956, co-invented and jointly owned with this application. These applications are incorporated herein by reference in their entirety. Attached Figure Description

[0003] The aspects and advantages of the embodiments provided herein are described in the following detailed description taken in conjunction with the accompanying drawings.

[0004] Throughout the accompanying drawings, reference numerals may be used repeatedly to indicate the correspondence between referenced elements. The drawings are provided to illustrate exemplary embodiments described herein and are not intended to limit the scope of this disclosure.

[0005] Figure 1 A simplified schematic diagram of an illustrative embodiment is shown.

[0006] Figure 2 The diagram shows the IR beam traveling between AFM and photothermal processes.

[0007] Figure 3 The shuttle between IR and Raman is shown.

[0008] Figure 4 The same objective lens used for AFM as for UV / vis light collection is shown.

[0009] Figure 5 Examples including laser scanning confocal microscopy and spectroscopy are shown.

[0010] Figure 6 It shows the relationship with Figure 2 The embodiments shown are related to those embodiments in which IR and UV / vis light are focused using the same objective lens.

[0011] Figure 7 An example of an IR source being a broadband source is shown.

[0012] Figure 8 Examples including mass spectrometry are shown.

[0013] Figure 9 An embodiment using total internal reflection irradiation with infrared radiation is shown. Detailed Implementation

[0014] definition

[0015] "Interacting with the sample" means bringing the probe tip close enough to the sample surface that one or more near-field interactions occur, such as attractive and / or repulsive tip-sample forces, and / or the generation and / or amplification of radiation scattered from the sample region near the probe tip. The interaction can be a contact mode, an intermittent contact / tapping mode, a non-contact mode, a pulsed force mode, and / or any transverse modulation mode. The interaction can be constant or periodic, as in the preferred embodiment. Periodic interactions can be sinusoidal or any arbitrary periodic waveform. Pulsed force modes and / or rapid force profiling techniques can also be used to periodically bring the probe to a desired level of interaction with the sample, followed by a hold period, and then subsequent probe retraction.

[0016] "Irradiation" means directing radiation toward an object, such as the surface of a sample, the tip of a probe, and / or the area of ​​probe-sample interaction. Irradiation may preferably include radiation in the infrared wavelength range, but other wavelengths may also be used. Irradiation may include any configuration of radiation sources, pulse generators, modulators, reflective elements, focusing elements, and any other beam directing or adjustment elements.

[0017] "Infrared source" and "infrared radiation source" refer to one or more light sources that generate or emit radiation in the infrared wavelength range (typically between 2 and 25 micrometers). The radiation source can be one of a large number of sources, including heat sources or silicon carbide rod sources, supercontinuum laser sources, frequency combs, difference frequency generators, sum frequency generators, harmonic generators, optical parametric oscillators (OPOs), optical parametric generators (OPGs), quantum cascade lasers (QCLs), nanosecond, picosecond, femtosecond, and attosecond laser systems, CO2 lasers, heated cantilever probes or other microheaters, and / or any other source that generates a radiation beam. In a preferred embodiment, the source emits infrared radiation, but it may instead emit radiation in other wavelength ranges, such as from ultraviolet to terahertz (THz). The source can be narrowband, for example, with a spectral width <10 cm. -1 or <1cm -1 Less, or it could be broadband, such as spectral width > 10cm -1 >100cm -1 or greater than 500cm -1 .

[0018] "UV / vis source" refers to a source of ultraviolet (UV) and / or visible (vis) light radiation. For example, a UV / vis source may include a gas laser, a laser diode, a superluminescent diode (SLD), or a UV and / or visible laser beam generated via sum-frequency or difference-frequency generation. It may also include any other UV and / or visible light source that can be focused onto a spot with a size of less than 2.5 micrometers, preferably less than 1 micrometer.

[0019] "Spectrum" refers to the measurement of one or more properties of a sample as a function of wavelength, or equivalently (and more commonly) as a function of wavenumber.

[0020] "Optical properties" refers to the optical properties of a sample, including but not limited to refractive index, absorption coefficient, reflectivity, absorptivity, the real and / or imaginary part of the refractive index, the real and / or imaginary part of the sample's dielectric function, and / or any property that can be mathematically derived from one or more of these optical properties.

[0021] "Optical response" refers to the result of the interaction between radiation and a sample. Optical response is related to one or more optical properties defined above. It can be radiation absorption, temperature increase, thermal expansion, photodynamic activity, light reflection and / or scattering, or other responses of the material due to its interaction with radiation.

[0022] A “signal indicating…” refers to a signal that is mathematically related to the property of interest. The signal can be an analog signal, a digital signal, and / or one or more digital signals stored in a computer or other digital electronic device. The signal can be voltage, current, or any other signal that can be easily converted and recorded. The signal can be mathematically identical to the property being measured, for example, explicitly an absolute phase signal or absorption coefficient. It can also be a signal that is mathematically related to one or more properties of interest, such as including linear or other scaling, offsetting, inversion, or even complex mathematical operations.

[0023] A scanning probe microscope (SPM) is a microscope in which a sharp probe interacts with a sample surface and then scans the surface while measuring one or more properties of the sample surface. A scanning probe microscope can be an atomic force microscope (AFM), which may include a cantilever probe with a sharp tip. SPMs typically include the ability to measure the motion, position, and / or other responses of the probe tip and / or an object to which the probe tip is attached (e.g., a cantilever or tuning fork or MEMS device). The most common approach involves using an optical lever system in which a laser beam bounces off the cantilever probe to measure the deflection of the cantilever. Alternatives include self-sensing techniques such as piezoresistive cantilevers, tuning forks, capacitive sensing, and other techniques. Other detection systems can measure other properties such as forces, force gradients, resonant frequencies, temperature, and / or other interactions with or responses to surface interactions.

[0024] A cantilever probe is typically a microfabricated cantilever made of silicon, silicon nitride, or other semiconductor-based materials. Probes can also be made of metallic and polymeric materials. Generally, a probe only needs to have a sharp tip that can interact with the sample and support some mechanism to detect the interaction, for example, by bending of the cantilever probe, or by changes in resistance, resonant frequency, or other properties that indicate the interaction between the probe and the sample over time.

[0025] A scanner is one or more scanning mechanisms used to generate relative translation between a probe and a sample, allowing the probe to interact with multiple locations on the sample and measure its properties. The scanning mechanism can move the probe, the sample, or a combination thereof. Scanning mechanisms are typically piezoelectric devices, but other mechanisms, such as electromagnetic, electrostatic, resistive, and other driven mechanisms, can also be employed to induce the desired movement in response to a given control signal or command. Scanners include, but are not limited to, piezoelectric tubes, piezoelectric stacks, piezoelectric-driven flexure platforms, voice coils, and other mechanisms for providing precise translation.

[0026] A “SPM controller” refers to a system that facilitates data acquisition and control of an AFM-IR system. The controller can be a single integrated electronic housing or can include multiple distributed components. Control elements can provide control over the positioning and / or scanning of the probe tip and / or sample. They can also collect data on probe deflection, motion, or other responses, providing control over radiation source power, polarization, steering, focusing, and / or other functions. Control elements, etc., can include computer program methods or digital logic methods and can be implemented using any combination of various computing devices (computers, personal electronic devices), analog and / or digital discrete circuit components (transistors, resistors, capacitors, inductors, diodes, etc.), programmable logic, microprocessors, microcontrollers, application-specific integrated circuits, or other circuit elements. A memory, configured to store computer programs, can be implemented together with discrete circuit components to perform one or more processes described herein.

[0027] A "lock-in amplifier" is a device and / or algorithm for demodulating the response of a system at one or more reference frequencies. Lock-in amplifiers can be electronic components comprising analog electronics, digital electronics, and combinations thereof. They can also be computational algorithms implemented on digital electronic devices such as microprocessors, field-programmable gate arrays (FPGAs), digital signal processors, and personal computers. Lock-in amplifiers can generate signals indicative of various measures of an oscillating system, including amplitude, phase, phase (X) and quadrature (Y) components, or any combination thereof. In this context, lock-in amplifiers can also generate such measurements at the reference frequency, higher harmonics of the reference frequency, and / or sideband frequencies of the reference frequency.

[0028] "Photothermal distortion" refers to changes in sample properties caused by the absorption of light energy (e.g., absorption of IR radiation). Photothermal distortion can refer to changes in refractive index, reflectivity, thermal expansion, surface deformation, or other effects that can be detected by the tip of an atomic force microscope and / or UV / visible light radiation beams.

[0029] Photothermal imaging and spectroscopy

[0030] Figure 1An embodiment of a rapid photothermal infrared imaging and spectroscopy system with sub-diffraction-limited spatial resolution is illustrated. An infrared radiation beam 100 is guided from an infrared source 102 at region 104 of a sample 106. The infrared source can be a tunable narrowband source, such as an infrared laser or a broadband source. If the beam 100 contains one or more wavelengths absorbed by the material components of the irradiated region of the sample, the absorbed radiation will cause heating of the absorbing components. The absorbed heat can be detected in one of two ways. First, it can be detected with a focused ultraviolet or visible (UV / vis) radiation beam. Alternatively, the UV / vis radiation source 108 is collimated using one or more lenses 110, then guided through a polarizing beam splitter 112 to a quarter-wave plate 114, and then focused by an objective lens 116 onto a portion of the sample region irradiated by the infrared radiation beam 100. Heating of the absorbing region of the sample can cause light reflected or more generally scattered from the sample surface to deviate from its normal trajectory without infrared light irradiating the sample. For example, the sample may deform due to thermal expansion, causing changes in the sample's reflection and / or refraction. Additionally, the sample or surrounding medium can be heated and alter the local refractive index of the sample. The resulting "thermal lens" can change the beam path of UV / vis light scattered, refracted, or reflected from the sample. Light returning from the sample can be collected by objective 116 (or alternatively, an additional objective placed below the sample, not shown) and then sent to receiver 120. In the case of light collected by illuminating objective 116, the collected light can pass through quarter-wave plate 114, causing the polarization to rotate 90 degrees relative to the incident beam. Polarizing beam splitter 112 then guides the polarized-rotated beam to receiver 120, which may include detector 121 or spectrometer 122, or both. Optionally, a portion of the beam 118 from the polarizing beam splitter can be blocked by filter 119. Filter 119 may have a central obstruction, for example, to block most of the undeflected central light, thereby increasing the dynamic range of detector 121 and / or spectrometer. That is, if the central portion of the undeflected beam is blocked, the detector can operate at higher gain and / or a longer integration time before saturation. Alternatively, an additional lens may be present in the collecting arm to focus the beam 118 onto a spot at or before the detector 121. In the case where the additional lens focuses the beam onto a column before the detector, a pinhole may be placed at the focused spot to block light scattered or reflected from areas outside the sample focal plane. The detector 121 may be a detector that measures the relative intensity of the beam incident upon it, such as a conventional photodiode, avalanche photodiode, photomultiplier tube, and / or other detectors that generate a signal indicating the intensity of light incident on the detector. Alternatively, the detector 121 may be a position-sensitive detector, such as a linear photodiode, a two- or four-segment detector, or a multi-detector array.In this configuration, the detector can also be sensitive to positional shifts in the reflected / scattered beam, such as due to angular deviations and / or lateral offsets in the beam. Alternatively, detector 121 may include a phase-sensitive detector and an interferometric detection scheme that generates a signal indicating the optical phase or optical phase shift of the beam incident on the detector. In these embodiments, the system can measure changes in intensity, beam angle, and / or optical delay caused by temperature variations in the sample due to the interaction or absorption of infrared light from the sample.

[0031] The infrared light source can be pulsed or modulated. For example, the controller 123 can generate a trigger or synchronization pulse that commands the light source to pulse at a specified rate. Alternatively, the light source can be based on an internal timing pulse and send the synchronization pulse back to the controller 123. Alternatively, the light source can have an external modulator 101 that periodically modulates its intensity. In a preferred embodiment, the light source is modulated or pulsed at a frequency exceeding 10 kHz, 100 kHz, or 1 MHz. Modulating infrared light at high frequencies reduces the effective thermal diffusion length, which would otherwise compromise the spatial resolution of the technique. The detected UV / vis light is then analyzed by the controller 123 and / or external signal conditioning / demodulation electronics. In one embodiment, the detector signal is analyzed by a lock-in amplifier or equivalent device to measure the amplitude of UV / vis modulation of the laser source at the modulation frequency or its harmonic frequencies. By using phase-sensitive detection, such as a lock-in amplifier, only the effect of infrared light absorbed by the sample and the resulting periodic deviation of the UV / vis beam caused by sample heating can be measured. By measuring the amplitude of UV / vis modulation at multiple locations on the sample 106, an image 128 of the infrared response of the sample can be created. A key aspect of this arrangement is that the infrared properties of the sample can be measured at a scale below the diffraction limit of the infrared light source irradiating the sample. Conversely, the spatial resolution is limited only by the spatial resolution limit of the irradiating UV / vis beam. This spatial resolution can be as low as λ / 2, where λ is the wavelength of the UV / vis beam. UV / vis modulation as a function of the wavelength of the infrared light source 102 can also be measured to generate the IR absorption, reflection, and / or transmission spectra 136 of the sample. In the case of narrowband sources, for example, the spectral linewidth is typically <10 cm⁻¹. -1 And preferably <1cm -1 The light source can generate a spectrum directly by measuring UV / vis modulation as a function of the emission wavelength (or equivalent ground wave number) of the infrared light source. This is possible with broadband light sources (typical linewidth > 100 cm). -1In this case, Fourier transform techniques may be needed to extract the wavelength dependence of UV / vis modulation and thus extract spectrum 136. In this case, light from IR source 102 passes through an interferometer including a beam splitter, a fixed mirror, and a moving mirror before it is incident on the sample. The moving mirror in the interferometer can be scanned at a series of different locations while monitoring UV / vis modulation to generate an interferogram. The interferogram can then be Fourier transformed to obtain the spectrum.

[0032] Spatially resolved maps 128 can be created in two main ways. First, the focused IR and UV / VIS spots can remain stationary, and the sample 106 can be scanned relative to these focused spots, for example, using a sample scanner 130. Alternatively, the UV / VIS beam can be scanned over the sample, for example, using a galvanometer scanning mirror used in laser scanning confocal microscopy. Note that the IR beam 100 can be stationary or scanning, depending on power requirements and the size of the focused spot. In one embodiment, the IR beam 100 is scanned synchronously with the UV / VIS spots such that the peak intensity of the IR beam and the center of the UV / VIS spot substantially overlap. Alternatively, the IR beam can be configured large enough to cover the range of travel of the scanned UV / VIS beam. In one embodiment, the IR source can be a heat source, such as a silicon carbide rod commonly used in Fourier transform infrared (FTIR) spectroscopy and microscopy. Alternatively, a small-area thermal emitter, for example from Axetris or NovaIR or other suppliers, can be used. In the case of a thermal emitter, it is desirable to modulate the temperature of the device or the output IR power. Some commercial small-area thermal emitters can be modulated to 100 Hz. AFM cantilever structures with integral resistance heaters can be modulated in the kHz range due to their small effective area and low thermal time constant. A thermal emitter fabricated by Susuma Noda and colleagues at Kyoto University can be modulated in the 10 kHz frequency range (doi:10.1038 / nmat4043). Various external modulators can also be employed, such as photoelastic modulators, high-speed choppers (e.g., from Scitec, up to 100 kHz), MEMS mirrors, piezoelectric deformable mirrors, and other modulators that can adjust the intensity, angle, and / or focused spot size of the infrared beam.

[0033] Figure 1 The ideal aspect of this device is that it can be used for both infrared photothermal optical microscopy and scanning probe microscopy measurements on the same platform. This can be achieved without manually moving samples from one instrument to another, thus supporting juxtaposition, sequential, and even simultaneous measurements in some cases.

[0034] In one embodiment, the UV / vis source may include a superluminescent diode (SLD). SLDs may be advantageous in this device because they have relatively short coherence lengths. Conventional lasers and laser diodes can have coherence lengths in the range of meters and millimeters. This can lead to problems as a light source for optical-thermal measurements because scattered and multiple reflections can self-interfere, causing undesirable parasitic oscillations in the measurement of IR light absorption with a UV-vis beam. Therefore, in one embodiment, a superluminescent diode is chosen as the UV-vis source. For example, superluminescent diodes manufactured by Exalos have spatial coherence in the range of 4–30 μm. These short coherence lengths mean that multiple reflections from a surface or scatterer, far exceeding the coherence length, will not strongly self-interfere at distances, thus resulting in an optical-thermal image with fewer interference artifacts. Qphotonics sells 405 nm superluminescent diodes coupled to single-mode fiber with a mode diameter of 3.6 μm. By using high NA and low aberration objectives, along with appropriate barrel lenses, light from single-mode fiber can be focused near the diffraction limit, thus achieving high spatial resolution without the optical interference problems associated with narrowband light sources.

[0035] In one embodiment, the image 128 generated by reading out IR absorption using a UV / vis beam can also be used as a “measurement scan” for higher resolution measurements by atomic force microscopy-based infrared spectroscopy (AFM-IR), scattering-scanning near-field optical microscopy (s-SNOM), tip-enhanced Raman spectroscopy (TERS), or any other probe-based microscopy scan, or for laser-based mass spectrometry, as described later. In the AFM-IR technique, the sample 106 is also irradiated by a beam 100 of infrared radiation from an IR source 102. In this case, if a portion of the irradiated area absorbs infrared light, the absorbing area can heat up and undergo thermal expansion, generating a force pulse on the probe tip 130 of the AFM. Alternatively, the IR radiation interacting with the sample can induce a force between the tip and the sample due to the interaction of an induced electric field. In either case, the force on the probe tip can cause the probe to bend, which can be detected optically or otherwise. In one embodiment, the same UV / vis laser system described above for reading out IR absorption can be used. In this configuration, a laser scanning mechanism (e.g., a scanning galvanometer) can be used to move the UV / vis laser beam from a region on the sample to the back of the cantilever. In one embodiment, the cantilever tilt angle and numerical aperture of objective 116 are selected such that light reflected from the AFM cantilever is reflected at an angle outside the collection angle of objective 116. For example, a Mitutoyo 20X 0.42NA long working distance objective can be used to focus the UV / vis laser spot onto the cantilever or the sample while still providing sufficient clearance for AFM deflection measurements outside the lens collection angle. The 20X 0.42NA objective has a half-angle of approximately 25°. Therefore, if the cantilever is tilted at 25 degrees or greater, the beam 124 reflected from the cantilever will pass outside the collection angle of objective 116 and can be collected by the position-sensitive detector 126. Despite this long working distance, the 20X 0.42NA objective can still focus the UV / vis beam into a spot with a diameter of less than 1 micrometer, a wavelength of approximately 670 nm for the light source 108, and an M2 beam quality of 1.2 or better. Similarly, a 10X 0.24NA 38mm working distance objective can be used. This objective can also achieve a focused spot diameter of slightly less than 1μm at light sources with wavelengths of 408nm or shorter. It has the advantage of a small collection angle of 14 degrees, which requires only a cantilever tilt of 7 degrees or more to keep the reflected beam outside the collection angle of the optics.

[0036] By utilizing a combined system of AFM-IR mapping incorporating UV / vis and IR absorption, rapid large-area mapping and extremely high spatial resolution IR mapping can be achieved. For example, a large area can be rapidly scanned using a UV / vis beam to obtain a measurement scan 128 with a spatial resolution of 0.2–1 μm. Smaller regions of interest 132 can then be identified within the measurement scan 128. These smaller regions 132 can then be measured using AFM-IR to obtain a high-resolution image 134 with spatial resolution down to the nanometer scale.

[0037] Advantageously, the receiver 120 that collects radiation reflected / scattered from the sample surface can be a detector 121 or a spectrometer 122 or a combination thereof. In one embodiment, the spectrometer 122 comprises a Raman spectrometer. Since the sample illumination beam is preferably in the UV or visible wavelength (or alternatively short-wavelength IR, e.g., 1064 nm), it can also be used to excite the Raman response in the sample. In this case, the backscattered / reflected light can be analyzed by a Raman spectrometer used for Raman-shifted photons. In this way, the same instrument can collect the infrared and Raman spectra of the same sample, and has submicron spatial resolution for both measurements.

[0038] Figure 2 An optical arrangement is shown in one embodiment, which uses the same objective lens to support both optical-thermal measurements and AFM-based measurements. Figure 2 A illustrates an arrangement for optical photothermal measurements. UV / vis light 200 passes through objective lens 202, where it is focused 204 onto region 206 of sample 208. Scattered and / or reflected light is transmitted upward through the objective lens and, according to... Figure 1 The methods described in the relevant texts are used for detection and analysis. Figure 2 B illustrates an arrangement for AFM-based measurements. In this arrangement, beam 210 is guided away from the center of the optical axis of objective 202. For example, beam 210 may be located near the outer diameter of the input aperture of objective 202. As beam 212 exits objective 202, it is guided to impact probe 214, such as an AFM cantilever probe. The reflected beam 216 is guided to an alternating optical path different from the incident beams 210 / 212 and exits the objective on a parallel but offset path 218. This offset allows for easy separation of the incident and emitted beams and guidance of the emitted beam 218, for example, by using mirror 220 to guide the reflected beam to position-sensitive detector 220 to measure the deflection of probe 214.

[0039] Figure 3One embodiment of the apparatus is shown, which includes top-side and side-angle illumination of a sample with an IR beam and high-resolution UV / vis readout. In this embodiment, the IR beam 308 illuminates the sample 306 at a low illumination angle. The IR beam 308 is focused onto a spot on the sample 306 using a focusing element 312, which may include one or more lenses and / or curved mirrors. In one embodiment, the focusing element 312 may be a parabolic mirror, such as an off-axis parabolic mirror. The UV / vis beam 300 is guided through an objective lens 302 to focus light 304 onto an area of ​​the sample 306. The cone angle 310 of the IR beam 308 can be selected such that it can be fitted within the working distance and angular clearance of the objective lens 302. For example, the objective lens 302 may be a 100X 0.7NA objective lens from Mitutoyo with a working distance of 6 mm. This working distance and the objective lens housing provide support for an IR illumination cone angle of approximately 32 degrees, corresponding to an illumination NA of 0.28 and an incident angle of 16 degrees. The illumination NA is sufficient to focus the IR radiation 308 into a sufficiently small spot to obtain the intensity required for optical-photothermal detection at the sample. For high spatial resolution, only a tightly focused UV / vis beam is required. The IR beam can be focused into a larger spot, provided the focused spot has sufficient intensity to produce a detectable deflection in the visible beam. Smaller IR illumination angles can also be used, for example, to provide more clearance between the IR beam 308 (and focusing element 312) and the sample 306.

[0040] In cases where higher NA focusing optics are required for UV / vis beams, side-angle illumination can be achieved using specially modified objectives. Figure 4 An embodiment involving a high NA objective 400 and side-angle illumination with an IR beam 406 is shown. In this case, the short working distance of a standard high NA objective may not provide sufficient clearance for side-angle illumination. For example, an objective with an NA of 0.85 or higher may have a working distance much less than 1 mm. In the case of ultra-high NA UV / visible light objectives, an illumination path for IR light can be created by fabricating a custom objective with an aperture or other clearance for side illumination. For example, the objective housing can be machined and, if necessary, a small portion of the edge of the finished objective can be machined. Figure 4 A high-NA objective lens 400 is shown, which has a UV / vis beam 402 focused onto a sample 404. A portion 406 of the objective lens 400 is cut off to provide a path for side-angle illumination by an IR beam 408.

[0041] Figure 5An embodiment combining photothermal IR spectroscopy and laser scanning confocal microscopy / spectroscopy is shown. IR source 502 focuses an IR radiation beam 504 onto sample 506. The sample can be scanned under the beam by scanner 508. Scanner 508 can be a piezoelectrically driven platform, a mechanical translation platform, or a combination thereof. It can be mechanical translation. The sample can also be measured by AFM probe 510 to measure its morphology and photothermal response. Sample 506 is also illuminated by a UV beam, visible beam, or near-infrared beam via light source 512. Light from light source 512 is collimated by lens 514 and then guided to beam splitter or dichroic mirror 516. A portion of the light is optionally guided toward scanning mirror 518, typically a pair of galvanometer-based steering mirrors. Light reflected from the galvanometer scanning mirror can be focused by scanning lens 520 to produce an intermediate focal point at 522. Tube lens 524, combined with objective lens 530, transfers the image of intermediate focal point 522 to the location on sample 506. As the galvanometer scanning mirror 518 moves, the position of the focused spot on the sample can be translated across the sample. If the focused spot of beam 504 is large relative to the scanning range provided by the scanning mirror 518, the IR focused spot can remain stationary, and the scanning mirror 518 can quickly map the photothermal response of the sample. Light reflected and / or scattered from object 506 is recaptured by objective lens 530 and reflected back into the incident light path. An optional beam splitter / dichroic mirror or removable mirror 526 can be used to provide an auxiliary optical path for white light illumination and / or a camera view of the sample. Light passing through or through beam splitter / dichroic mirror 526 continues along the incident light path back to beam splitter / dichroic mirror 516. In this case, we now consider light passing through beam splitter / dichroic mirror 516 and then entering optional focusing lens 530, where focusing lens 530 focuses the light onto a point on a confocal aperture or pinhole. The pinhole allows light to pass through, is confocal with the sample focal plane, and blocks the focused light. The aperture at this location can be an adjustable aperture or a selectable pinhole with various sizes to allow for appropriate trade-offs between signal and depth of focus. Light passing through pinhole 532 can be coupled to fiber optic 534 or directly to detector / spectrometer assembly 535. Detector / spectrometer 535 may include a mirror / dichroic mirror / beam splitter 536 to split or direct collected light along a path to either or both of UV / visible detector 540 or spectrometer 538. For example, 536 may be a rotatable or flip-up mirror to direct light to detector 540 or spectrometer 538 or 536, and may be a beam splitter to distribute light between two paths. In one embodiment, spectrometer 538 is a Raman spectrometer, allowing the system to perform complementary measurements of IR and Raman spectroscopy simultaneously on the same sample, or even if desired. When using a spectrometer, beam splitter 536 may be a dichroic mirror that reflects or transmits the excitation wavelength while reflecting or transmitting the Raman-shifted light in the opposite direction.In this way, light can be separated by wavelength and analyzed individually for photothermal IR absorption measurements at the excitation wavelength of light source 512, and Raman spectroscopy measurements can be performed at spectrometer 538 using wavelength-shifted light.

[0042] Figure 6 It shows the relationship with Figure 2 The embodiments shown are related to those described above, in which IR and UV / vis light are focused using the same objective lens. An IR light source 600 emits an IR radiation beam 601 toward an optional reflector 602, which reflects the beam toward an objective lens 604, focusing the beam 606 at the objective lens 604 onto a point on the sample 608. The objective lens 606 is preferably a reflecting objective lens, such as a Cassegrain / Schwarzschild objective lens, so that it can focus both UV / Vis and IR light at the same point in space. The objective lens 606 can also be a refractive objective lens, such as a lens made of an IR-transparent material (e.g., ZnSe). The IR light absorbed by the sample 608 causes an increase in temperature within the sample, resulting in photothermal distortions in the sample, such as changes in refractive index, reflectivity, and / or surface deformation. The UV / vis light source 624 is collimated by a lens 626 and reflected by a dichroic mirror or beam splitter 628 through the same objective lens 604, and focused onto substantially the same area of ​​the sample where the IR beam is focused. Temperature increases in the sample and the resulting photothermal distortion of the sample can cause changes in the intensity, angle, and / or optical phase of the reflected / scattered visible light from source 626. The scattered / reflected UV / vis light is collected by objective lens 604 and transmitted to dichroic mirror / beam splitter 614, where it is directed to receiver 618. Receiver 618 may include UV / vis detector 620 and / or spectrometer 622, as previously referenced. Figure 1 and Figure 5 The sample 608 can be scanned at focused UV / vis and IR points using scanner 610 to provide an IR absorption map of the sample. The wavelength of the IR source 600 can be scanned to obtain spectral measurements of the sample 608. Scanner 610 may include a large-stroke (mm to cm scale) mechanical platform for coarse imaging and a piezoelectric platform for fine imaging via UV / vis photothermal measurements or by reading the forces on the AFM probe caused by IR radiation incident on the sample using AFM probe 612.

[0043] Figure 7 An embodiment of a broadband IR source is shown, such as a silicon carbide rod or other heat source. The broadband IR source 700 emits a radiation beam 702 comprising multiple wavelengths, preferably including a wide wavelength range, for example, a wavelength range of 2.5 nm. -10Micrometers or larger. A broadband IR beam 702 is guided toward a beam splitter 704, where the beam is split into two paths. In one path, the broadband IR light strikes a fixed mirror 708, and in the other path, it strikes a movable mirror 706. The two beams are recombined with a relative phase shift determined by the position of the movable mirror 706. The combined beam is then guided through or directed to an optional modulator 710, which modulates the intensity and / or angle of the IR beam. The modulated beam is reflected from an optional mirror 712 and guided through an objective lens 714, where it is focused 716 onto a sample 718. The IR light absorbed by the sample produces photothermal distortion, which is read out by an AFM probe 722 or a UV / visible beam, as previously described. In the case of readout via an AFM probe, the modulation frequency of the modulator 710 can be set to correspond substantially to the resonant frequency of the probe 722. In this configuration, the detection of the photothermal deflection of the AFM cantilever is amplified by the quality factor of the cantilever resonance. This resonant amplification allows the use of a heat source (i.e., a silicon carbide rod), which has a much lower cost and much lower brightness than an IR laser. The modulator 710 can also be used to generate modulation in the excitation, which can then be used for locked detection of UV-vis light intensity. The modulator frequency can also be set to correspond to the resonant frequency of the resonant amplifier, for example, as described in U.S. Patent Application 20140361150.

[0044] Current devices can also be combined with mass spectrometry, such as... Figure 8 As shown. In this case, an IR laser and / or a UV / vis source can be used to thermally desorb material from the sample, which can then be analyzed in a mass spectrometer. For example... Figure 8As shown, light from IR source 800 or UV / vis source 812 can be focused onto sample 806 using objective lens 804. The focusing intensity of the selected laser source is set sufficient to desorb and / or evaporate material from sample 806. At least a portion of the desorbed plume is collected by collection tube 808, which then transfers the desorbed material to mass spectrometer 810 for analysis. Mass spectrometer 810 can then analyze the chemical content of the desorbed material by generating a spectrum of the desorbed molecular mass. The sample can be scanned under the desorbed beam by scanner 808 to generate a mass spectrometry array or an image of a selected mass. As previously described, the IR beam combined with UV / vis readings can also measure the IR and / or Raman spectra of the same region. Specifically, IR light from source 800 is focused onto sample 806, and the resulting photothermal distortion can be read out using UV / vis beam and / or via AFM probe 814. UV / vis light is collected by objective lens 804 and directed to receiver 816, which may include a UV / vis detector, a spectrometer, or both, as described above. The UV / vis measurement of the photothermal deformation of samples provides a very rapid and efficient means of performing IR measurements on samples to select regions for analysis by thermal desorption mass spectrometry. This platform can provide any combination of AFM, IR spectroscopy, laser scanning confocal microscopy, Raman spectroscopy, and mass spectrometry. UV / vis spectroscopy can also be performed using variable wavelength or broadband UV / vis light sources.

[0045] Figure 9 An embodiment employing total internal reflection illumination with infrared radiation is illustrated. An IR radiation beam 900 is focused to pass through an infrared transparent substrate 902, such as a prism. A sample 904 is mounted or deposited on the prism 902. The illumination angle of the beam 900 is selected to provide total internal reflection at the upper surface of the prism 902. In this case, the sample can only be illuminated if the refractive index is sufficient to allow transmission into the sample or through an evanescent field propagating into the sample. The reflected beam 906 can be analyzed by an IR detector to provide a spectral characterization of the sample, down to the scale of spatial resolution limited by the diffraction limit of the incident beam 900. As previously described, sub-diffraction limit measurements of IR absorption can be performed using a probe microscope 908 and / or a UV / vis beam from a light source 910. Light from the UV / vis source 910 is focused by an objective lens 912, and the reflected / scattered light can be collected by the same objective lens. At least a portion of the collected light is directed toward a receiver 914, which may include a UV / vis detector, a spectrometer, or both. Due to the transient illumination, the IR beam can have a very limited penetration depth into the sample, providing improved surface sensitivity, especially to the surface closest to the IR transparent prism 902.

[0046] The embodiments described herein are exemplary. Modifications, rearrangements, substitutions of processes, substitutions of elements, etc., may be made to these embodiments, and these modifications are still included within the teachings set forth herein. One or more steps, processes, or methods described herein may be performed by one or more appropriately programmed processing and / or digital devices.

[0047] Depending on the embodiment, certain actions, events, or functions of any method steps described herein may be performed in a different order, and may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary for the implementation of the algorithm). Furthermore, in some embodiments, actions or events may be performed concurrently rather than sequentially.

[0048] The various illustrative logic blocks, optical and SPM control elements, and method steps described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this hardware and software interchangeability, the various illustrative components, blocks, modules, and steps have been generally described above in terms of functionality. Whether this functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the system as a whole. The described functionality can be implemented differently for each specific application, but such implementation decisions should not be construed as departing from the scope of this disclosure.

[0049] The various illustrative logic blocks and modules described in conjunction with the embodiments disclosed herein can be implemented or executed by a machine, such as a processor configured with specific instructions, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. The processor may be a microprocessor, or it may be a controller, a microcontroller, or a state machine, a combination thereof, etc. The processor may also be implemented as a combination of computing devices, such as a DSP and a microprocessor, multiple microprocessors, a combination of one or more microprocessors incorporating a DSP core, or any other such configuration.

[0050] Elements of the methods, processes, or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly in hardware, in a software module executed by a processor, or a combination of both. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of computer-readable storage medium known in the art. An exemplary storage medium may be coupled to a processor such that the processor can read information from and write information to the storage medium. Alternatively, the storage medium may be an integral part of the processor. The processor and storage medium may reside in an ASIC. The software module may include computer-executable instructions that cause the hardware processor to execute the computer-executable instructions.

[0051] Unless otherwise expressly stated, or otherwise understood in the context as used, conditional statements used herein, such as “may,” “possibly,” “can,” “for example,” etc., are generally intended to convey that certain embodiments include, while other embodiments do not, certain features, elements, and / or states. Therefore, such conditional statements are not generally intended to imply that one or more embodiments require features, elements, and / or states in any way, or that one or more embodiments must include logic for determining, with or without author input or prompting, whether such features, elements, and / or states are included in or will be performed in any particular embodiment. The terms “comprising,” “including,” “having,” “involving,” etc., are synonyms and are used in an open-ended manner, not excluding additional elements, features, actions, operations, etc. Furthermore, the term “or” is used in its inclusive sense (rather than its exclusive sense), and thus, when used, for example, to connect lists of elements, the term “or” indicates one, some, or all of the elements in the list.

[0052] Unless otherwise specifically stated, disjunctive languages ​​such as the phrase “at least one of X, Y or Z” are understood in the context to generally refer to items, terms, etc., which may be X, Y or Z, or any combination thereof (e.g., X, Y and / or Z). Therefore, such disjunctive languages ​​are generally not intended and should not imply that certain embodiments require the presence of at least one of X, at least one of Y, or at least one of Z.

[0053] The terms “about” or “approximately” are synonyms and are used to indicate that the value modified by the term has a range of understanding associated with it, wherein the range may be ±20%, ±15%, ±10%, ±5%, or ±1%. The term “substantially” is used to indicate that a result (e.g., a measurement) is close to a target value, wherein close may mean, for example, that the result is within 80%, within 90%, within 95%, or within 99% of the value.

[0054] Unless otherwise expressly stated, articles such as “a” or “an” should generally be interpreted as including one or more of the described articles. Therefore, phrases such as “an apparatus configured to” are intended to include one or more of the described apparatuses. Such one or more of the described apparatuses may also be configured collectively to perform the described record. For example, “a processor configured to perform records A, B, and C” could include a first processor configured to perform record A, which works in conjunction with a second processor configured to perform records B and C.

[0055] While the above detailed description has shown, described, and pointed out novel features applicable to the illustrative embodiments, it should be understood that various omissions, substitutions, and changes may be made to the form and details of the illustrated apparatus or method without departing from the spirit of the disclosure. As will be appreciated, some embodiments described herein may be implemented in forms that do not provide all the features and benefits set forth herein, as some features may be used or implemented separately from other features. All variations within the meaning and scope of the claims are included within their scope.

Claims

1. An apparatus for rapidly characterizing samples using submicron infrared radiation, the apparatus comprising: An infrared radiation source is configured to irradiate a sample with an infrared radiation beam to create an infrared irradiated area. An ultraviolet-visible radiation source configured to irradiate at least one region of the infrared irradiation region of the sample with an ultraviolet-visible beam; A collector configured to collect at least a portion of ultraviolet-visible light as collected light, said ultraviolet-visible light being at least one of scattering, reflection, and refraction from said sample; A detector configured to analyze the collected light to indicate infrared absorption in at least one region of the infrared-illuminated area; as well as A Raman spectrometer configured to analyze the collected light to analyze the Raman response of the sample. The area of ​​the sample irradiated by the ultraviolet-visible beam is smaller than the area of ​​the sample irradiated by the infrared radiation beam.

2. An apparatus for rapidly characterizing samples using submicron infrared radiation, the apparatus comprising: An infrared radiation source is configured to irradiate a sample with an infrared radiation beam to create an infrared irradiated area. An ultraviolet-visible radiation source configured to irradiate at least one region of the infrared irradiation region of the sample with an ultraviolet-visible beam; A collector configured to collect at least a portion of ultraviolet-visible light as collected light, said ultraviolet-visible light being at least one of scattering, reflection, and refraction from said sample; A detector configured to analyze the collected light to indicate infrared absorption in at least one region of the infrared-illuminated area; as well as A Raman spectrometer configured to analyze the collected light to analyze the Raman response of the sample. The collector includes an objective lens, which is further configured to focus at least one of the infrared radiation beam and the ultraviolet-visible beam onto the sample.

3. An apparatus for rapidly characterizing samples using submicron infrared radiation, the apparatus comprising: An infrared radiation source is configured to irradiate a sample with an infrared radiation beam to create an infrared irradiated area. An ultraviolet-visible radiation source configured to irradiate at least one region of the infrared irradiation region of the sample with an ultraviolet-visible beam; A collector configured to collect at least a portion of ultraviolet-visible light as collected light, said ultraviolet-visible light being at least one of scattering, reflection, and refraction from said sample; A detector configured to analyze the collected light to indicate infrared absorption in at least one region of the infrared-illuminated area; as well as A Raman spectrometer configured to analyze the collected light to analyze the Raman response of the sample. The collector includes an objective lens, and the ultraviolet-visible radiation source and the objective lens are arranged such that the ultraviolet-visible light beam is focused onto the sample through the objective lens and the ultraviolet-visible light is collected through the objective lens.

4. A method for rapidly characterizing a sample using submicron infrared radiation, the method comprising: The sample is irradiated with an infrared radiation beam to create an infrared irradiated area; At least one region of the infrared irradiation area of ​​the sample is irradiated with an ultraviolet-visible beam; At least a portion of ultraviolet-visible light is collected as collected light, wherein the ultraviolet-visible light is at least one of scattering, refraction, and reflection from the sample; Analyze the collected light to determine the infrared absorption in the infrared irradiated area; as well as The collected light was analyzed to detect the Raman response of the sample. The area of ​​the sample irradiated by the ultraviolet-visible beam is smaller than the area of ​​the sample irradiated by the infrared radiation beam.

5. A method for rapidly characterizing a sample using submicron infrared radiation using the apparatus of claim 2, the method comprising: The sample is irradiated with an infrared radiation beam to create an infrared irradiated area; At least one region of the infrared irradiation area of ​​the sample is irradiated with an ultraviolet-visible beam; At least a portion of ultraviolet-visible light is collected as collected light, wherein the ultraviolet-visible light is at least one of scattering, refraction, and reflection from the sample; Analyze the collected light to determine the infrared absorption in the infrared irradiated area; as well as The collected light is analyzed to detect the Raman response of the sample.

6. A method for performing rapid characterization of a sample using submicron infrared radiation using the apparatus of claim 3, the method comprising: The sample is irradiated with an infrared radiation beam to create an infrared irradiated area; At least one region of the infrared irradiation area of ​​the sample is irradiated with an ultraviolet-visible beam; At least a portion of ultraviolet-visible light is collected as collected light, wherein the ultraviolet-visible light is at least one of scattering, refraction, and reflection from the sample; Analyze the collected light to determine the infrared absorption in the infrared irradiated area; as well as The collected light is analyzed to detect the Raman response of the sample.

7. A method for rapidly characterizing a sample using submicron infrared radiation, the method comprising: The sample is irradiated with an infrared radiation beam from a broadband infrared radiation source to create an infrared irradiated area. At least one region of the infrared irradiation area of ​​the sample is irradiated with an ultraviolet-visible beam; At least a portion of ultraviolet-visible light is collected as collected light, wherein the ultraviolet-visible light is at least one of scattering, refraction, and reflection from the sample; Analyze the collected light to determine the infrared absorption in the infrared irradiated area; as well as The collected light was analyzed to detect the Raman response of the sample. The area of ​​the sample irradiated by the ultraviolet-visible beam is smaller than the area of ​​the sample irradiated by the infrared radiation beam.

8. A method for rapidly characterizing a sample using submicron infrared radiation using the apparatus of claim 2, the method comprising: The sample is irradiated with an infrared radiation beam from a broadband infrared radiation source to create an infrared irradiated area. At least one region of the infrared irradiation area of ​​the sample is irradiated with an ultraviolet-visible beam; At least a portion of ultraviolet-visible light is collected as collected light, wherein the ultraviolet-visible light is at least one of scattering, refraction, and reflection from the sample; Analyze the collected light to determine the infrared absorption in the infrared irradiated area; as well as The collected light is analyzed to detect the Raman response of the sample.

9. A method for performing rapid characterization of a sample using submicron infrared radiation using the apparatus of claim 3, the method comprising: The sample is irradiated with an infrared radiation beam from a broadband infrared radiation source to create an infrared irradiated area. At least one region of the infrared irradiation area of ​​the sample is irradiated with an ultraviolet-visible beam; At least a portion of ultraviolet-visible light is collected as collected light, wherein the ultraviolet-visible light is at least one of scattering, refraction, and reflection from the sample; Analyze the collected light to determine the infrared absorption in the infrared irradiated area; as well as The collected light is analyzed to detect the Raman response of the sample.

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