Apparatus and method for inverse photoemission spectroscopy

Abstract

Disclosed are an apparatus and method for inverse photoemission spectroscopy, the apparatus comprising: a support which supports a sample; an electron gun which irradiates electrons to the sample; a curved mirror which is disposed above the sample and collects and reflects photons emitted from the sample; a reflective mirror which receives and reflects the photons reflected from the curved mirror; and a detector which detects the reflected photons, wherein the support, the electron gun, the curved mirror, the reflective mirror, and the detector are provided in a single vacuum chamber.

Description

Inverse photoelectron spectroscopy apparatus and method

[0001] The present invention relates to an inverse photoelectron spectroscopy device and method, and more particularly, to an inverse photoelectron spectroscopy device and method in which an optical system is provided entirely in a single chamber.

[0002] Recently, various research and development using organic materials, such as organic light-emitting diodes (OLEDs), organic photovoltaics (OPVs), and organic thin film transistors (OTFTs), are underway, and industrial demand is increasing. Accordingly, it is becoming important to understand the factors that affect the operation of the device, such as the transport method of electrons and holes within the device and the energy barrier between different organic materials by identifying the energy levels of organic materials. The energy level that many researchers mainly measure is the optical bandgap, which is measured using a single material. However, in actual devices, excitons are formed when electrons and holes combine, and the electrons and holes are transferred from other materials that make up the device, which also changes the energy structure. The bandgap in which the actual electron and hole transport occurs after these internal and external influences combine is called the transport bandgap.

[0003] There is a difference between the optical band gap, which is measured in a single measurement without external influence, and the transport band gap of a material operating in an actual device. Therefore, in semiconductors, where controlling the flow of electrons and holes is crucial, accurate measurement and analysis of the transport band gap plays a very crucial role. The cold energy level (highest occupied molecular orbital, HOMO) in the transport band gap can be measured using photoemission spectroscopy (PES), which measures photoelectrons emitted by the photoelectric effect caused by injecting ultraviolet light.

[0004] One analytical method for measuring the lowest unoccupied molecular orbital (LUMO) is inverse photoemission spectroscopy (IPES). IPES, which operates in reverse to PES, injects electrons with well-defined kinetic energy, stabilizes them, and measures the photons they emit to analyze energy levels. Unlike PES, inverse photoemission spectroscopy has a low yield in the process of electron injection and photon emission, resulting in weaker signal intensities compared to other analytical instruments.

[0005] Accordingly, efforts have been made to use high-performance photon detectors and high-resolution electron guns, but the long measurement time and low signal intensity compared to PES and other material property measurement technologies have been obstacles to the commercialization of IPES technology.

[0006] Furthermore, to increase low yields, conventional IPES technology typically places detectors as close to the sample as possible or uses multiple detectors simultaneously to add up the measured values. However, because photons are emitted radially from the sample surface, most are lost and discarded. Efforts to improve these issues have included adding multiple components, but these solutions often require a large amount of space inside and outside the chamber for the analysis device, and adjustment of individual components is difficult.

[0007] The present invention has been devised to solve the above problems, and aims to provide an inverse photoelectron spectroscopy device that increases usability through simplification of the structure and improves photon detection performance through shortening of the optical path.

[0008] As a means for achieving the above-described object, the present invention discloses an inverse photoelectron spectroscopy apparatus including a support for supporting a sample; an electron gun for irradiating electrons to the sample; a curved mirror disposed on an upper portion of the sample and capturing and reflecting photons emitted from the sample; a reflecting mirror for receiving and reflecting photons reflected from the curved mirror; and a detector for detecting the reflected photons; wherein the support, the electron gun, the curved mirror, the reflecting mirror, and the detector are provided in a single vacuum chamber.

[0009] Here, the curved mirror can reflect photons emitted from the sample and focus them at a focal point.

[0010] Here, the reflective mirror is arranged parallel to and spaced apart from the curved mirror, and can reflect photons reflected from the curved mirror so that they are incident on the detector.

[0011] Here, the detectors may be arranged parallel to the electron gun at regular intervals.

[0012] Here, the curved mirror includes a through hole through which electrons irradiated on the sample pass; and a reflective surface formed into a curved surface to surround the sample and reflect photons emitted from the sample by the electrons that pass through the through hole; and the through hole can be formed on the reflective surface.

[0013] The diameter of the surface on which the electrons are incident may be equal to or greater than the diameter of the reflective surface.

[0014] Here, the diameter shape of the above-mentioned through hole can be formed into any one of a circular, oval, triangular, square, rectangular, polygonal, and slit shape.

[0015] In addition, the present invention discloses a reverse photoelectron spectroscopy method, which comprises the steps of: irradiating electrons to a sample through a curved mirror to achieve the above-described purpose; capturing and reflecting photons emitted from the sample irradiated with the electrons by the curved mirror; reflecting the reflected photons by a reflecting mirror; and detecting the reflected photons by a detector.

[0016] The inverse photoelectron spectroscopy device of the present invention can minimize the optical path as the optical system is configured inside a single vacuum chamber.

[0017] In addition, the inverse photoelectron spectroscopy device of the present invention can improve spectral performance by reducing interference with photons in the air and reducing the degree of exposure to the external environment.

[0018] In addition, the inverse photoelectron spectroscopy device of the present invention can ensure convenience for users as it can be integrated into a single vacuum chamber.

[0019] Figure 1 is an exemplary diagram showing a reverse photoelectron spectroscopy device according to one embodiment of the present invention.

[0020] FIG. 2 is an exemplary diagram showing a curved mirror according to one embodiment of the present invention.

[0021] Figure 3 is a graph showing the optical path in the reverse photoelectron spectroscopy device of the present invention.

[0022] Figure 4 is an image showing the results of simulating the optical path in the reverse photovoltaic spectrometer of the present invention.

[0023] FIG. 5 is an image showing the amount of light in a reflective mirror and detector according to one embodiment of the present invention.

[0024] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0025] Throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0026] The terms "about," "substantially," and the like, as used herein, are used to mean at or near the numerical value when manufacturing and material tolerances inherent to the meanings stated are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that contain precise or absolute numerical values ​​to aid understanding of the present disclosure. Furthermore, throughout the present disclosure, the terms "step of doing" or "step of" do not mean "step for."

[0027] Those skilled in the art will appreciate that the gist of the present invention can be applied in a variety of ways, and therefore the scope of the present invention is not limited to the following examples. The scope of the present invention extends to any portion that would be readily replaceable or modified by a person skilled in the art using prior art, based on the matters set forth in the claims.

[0028] Hereinafter, the present invention will be described in more detail with reference to the attached drawings when necessary.

[0029] <Reverse photoelectron spectroscopy device>

[0030] As a means for achieving the above-described purpose, the present invention discloses an inverse photoelectron spectroscopy device in which an optical system is integrated within a single vacuum chamber by reflecting photons emitted from an irradiated sample through a curved mirror and reflecting the reflected photons again through a reflecting mirror to reach a detector.

[0031] FIG. 1 is an exemplary diagram showing an inverse photoelectron spectroscopy device according to one embodiment of the present invention. Referring to FIG. 1, it can be seen that the inverse photoelectron spectroscopy device of the present invention includes a support (110) for supporting a sample; an electron gun (120) for irradiating electrons to the sample; a curved mirror (130) disposed on an upper portion of the sample and capturing and reflecting photons emitted from the sample; a reflecting mirror (140) for receiving and reflecting photons reflected from the curved mirror (130); and a detector (150) for detecting the reflected photons. Furthermore, it can be seen that the support (110), the electron gun (120), the curved mirror (130), the reflecting mirror (140), and the detector (150) are provided within a single vacuum chamber (160).

[0032] Here, the electron gun (120) can inject low-energy electrons with high resolution while affecting organic materials as little as possible. This electron gun (120) can be implemented as an electron gun with a simple lens configuration and capable of obtaining a high beam current. That is, the electron gun (120) can be configured with one cathode and three cylindrical lenses (e.g., an extraction lens, a focus lens, and a final lens), and can have a structure in which a spacer is used between each lens and the cathode so that each lens can maintain its own voltage while maintaining an insulating state. Here, the spacer can be implemented as an insulator made of ceramics.

[0033] Fig. 2 is an exemplary diagram showing a curved mirror according to one embodiment of the present invention. Referring to Fig. 2, the curved mirror (130) of the present invention includes a through hole (131) through which electrons incident on a sample pass, and a reflective surface (133) formed in a curved surface to surround the sample and capture photons emitted from the sample by the penetrated electrons. The through hole (131) may be formed on the reflective surface (133).

[0034] In addition, the curved mirror of the present invention may have a diameter of a surface onto which the electrons are incident, which may be equal to or larger than the diameter of the reflective surface. The curved mirror in Fig. 2a is an example of a curved mirror in which the size of the penetration diameter (131-1) of the surface onto which the electrons are incident and the size of the penetration diameter (131-1) of the surface from which the electrons are emitted are the same. The curved mirror in Fig. 2b is an example of a curved mirror in which the size of the penetration diameter (131-2) of the surface onto which the electrons are incident is larger than the size of the penetration diameter (131-3) of the surface from which the electrons are emitted. In other words, the penetration hole (131) of the curved mirror in Fig. 2b may have a shape that gradually narrows from the penetration diameter of the surface onto which the electrons are incident to the penetration diameter of the surface from which the electrons are emitted.

[0035] In Fig. 2, all of the through holes (131) are implemented in a circular shape, but there is no limitation on the shape of the through holes. The curved mirror of the present invention may have a diameter shape of a surface on which electrons are incident, formed in any one of a circle, an ellipse, a triangle, a square, a rectangle, a polygon, and a slit shape. In addition, the diameter shape of the reflective surface of the through hole may be formed in any one of a circle, an ellipse, a triangle, a square, a rectangle, a polygon, and a slit shape.

[0036] Meanwhile, the diameter of the penetration hole can be designed in various ways. That is, the diameter of the penetration hole and the size of the curved mirror can be adjusted depending on the size of the diameter of the electron beam fired from the electron gun.

[0037] The above reflective surface may be formed into a curved shape to increase the ability to capture photons emitted from the sample. Furthermore, the reflective surface may be formed in consideration of an optimized focal length and an emission trajectory of photons emitted from the sample, and may be formed in any one of an elliptical shape, a hemisphere shape, a parabolic shape, and a free-form shape. According to one embodiment of the present invention, the shape of the curved mirror may be a 1 / 4 ellipse shape with a=50 and b=30. Here, a is the horizontal length of the ellipse, and b is the vertical length of the ellipse.

[0038] The above curved mirror can be implemented with a material having excellent reflectivity at ultraviolet (UV) and vacuum UV wavelengths. In an embodiment, the curved mirror can be implemented with a bare aluminum metal mirror. The curved mirror can capture and reflect photons emitted from a sample. At this time, the curved mirror is arranged to surround the sample, so that the photons emitted from the sample can be reflected so as to be focused toward a focal point. In addition, as the curved mirror focuses the photons toward a focal point, the effect of increasing the reflection efficiency of the reflective mirror and the detection efficiency of the detector, which will be described later, can be expected.

[0039] The photons focused toward the focal point can be reflected through a reflective mirror arranged parallel to and spaced apart from the curved mirror. The reflective mirror is arranged parallel to and spaced apart from the curved mirror, and can reflect the photons reflected from the curved mirror so that they are incident on the detector.

[0040] The above reflective mirror can be implemented with a material (e.g., bare aluminum metal) having excellent reflectivity at ultraviolet (UV) and vacuum UV wavelengths, similar to the curved mirror described above.

[0041] In FIGS. 3 and 4, the reflective mirrors are all implemented in a plane shape, but there is no limitation on the shape of the reflective mirrors. The shape of the reflective mirror may be appropriately selected to increase the efficiency of focusing photons reflected from the curved mirror onto a detector. More specifically, the reflective surface of the reflective mirror is formed in consideration of an optimized focal length and a reflection trajectory of photons reflected from the curved mirror, and may be formed in any one shape among a plane shape, an elliptical shape, a hemisphere shape, a parabolic shape, and a free-form shape.

[0042] Meanwhile, the above-described reflective mirror may also function as a mirror filter. The above-described mirror filter refers to a mirror that reflects photons to be detected and filters external photons that act as noise. In order to use the above-described reflective mirror as a mirror filter, the above-described reflective mirror may be, for example, an excimer laser mirror. The above-described excimer laser is a high-power ultraviolet laser that uses a gas (KrF, ArF, F2, XeCl, etc.) as a medium, is pulsed light, outputs power of about 5 to 200 W, and is mainly used in chemical reaction processes or medical fields. The above-described excimer laser mirror refers to a mirror that reflects the unique wavelength of each excimer laser described above.

[0043] Excimer laser mirrors that can be used as the above-mentioned reflection mirrors include, for example, a KrF excimer laser mirror (hereinafter referred to as a “KrF mirror filter”), an ArF excimer laser mirror (hereinafter referred to as an “ArF mirror filter”), an F2 excimer laser mirror (hereinafter referred to as an “F2 mirror filter”), a XeCl excimer laser mirror (hereinafter referred to as a “XeCl mirror filter”), etc., and it is also possible to manufacture and use a mirror that reflects only a specific wavelength as needed.

[0044] In the present invention, the detector may be included in the same chamber as the optical system (including the support, electron gun, curved mirror, and reflective mirror), and is not limited to a specific location. For example, the detector may be arranged parallel to the electron gun at a constant interval to detect photons reflected by the reflective mirror. According to one embodiment of the present invention, the electron gun and the detector may be arranged parallel to the same axis to miniaturize the device.

[0045] With the detectors arranged as described above, the optical system of the inverse photoelectron spectroscopy device of the present invention can be entirely housed within a single vacuum chamber. By arranging the entire optical system within a single vacuum chamber, the device can be miniaturized, and furthermore, the optical path taken by photons emitted from a sample to reach the detector can be shortened, effectively blocking external variables.

[0046] The above detector is not limited to a specific detector type. Any type that is easy to detect photons may be used. In an embodiment of the present invention, the detector may be a photomultiplier tube type, capable of detecting photons reflected by the reflective mirror. A photomultiplier tube (PMT) can amplify incident photons.

[0047] These photomultipliers are easy to use in a vacuum and are sensitive to the amplification of low-energy photons of a specific wavelength. That is, photomultipliers can convert irregularly varying signals resulting from light particles reflected from a reflective mirror into an analog signal of constant intensity and period through a photon counter.

[0048] Fig. 3 is a graph showing the optical path in the inverse photoelectron spectroscopy device of the present invention. More specifically, in Fig. 3, point F1 (0, 0) represents the start point of photons emitted from a sample, and point F2 (80, 0) represents the focal point where the emitted photons are reflected through a curved mirror and then collected.

[0049] Referring to FIG. 3, the inverse photoelectron spectroscopy device of the present invention uses a curved mirror designed with a size of a=50 and b=30, so it can be confirmed that photons emitted from point F1 are focused to point F2.

[0050] In addition, by arranging a reflective mirror parallel to the curved mirror in the middle of the path of the photons thus collected, the photons reflected by the curved mirror can be reflected, and by installing a detector on the path of the reflected photons, the optical path can be shortened, and at the same time, the detection efficiency of the photons can be expected to increase.

[0051] Figure 4 is an image showing the results of simulating the optical path in the reverse photovoltaic spectrometer of the present invention. More specifically, the blue solid line represents the path of photons emitted from a sample, the green solid line represents the path of photons reflected by a curved mirror, and the red solid line represents the path of photons reflected by a reflective mirror.

[0052] Referring to Fig. 4, it can be confirmed that the photons reach the reflective mirror while reducing the loss of the photons through the curved mirror designed to be focused at a focus when reflecting the photons emitted from the sample. In addition, the photons reflected through the curved mirror can be reflected in a form that is concentrated toward the focus rather than in a parallel light form. Therefore, by installing the reflective mirror on the path of the photons, it is possible to minimize the loss of the photons while reducing the optical path until they reach the detector, which is expected to have the effect of increasing the detection efficiency.

[0053] Figure 5 is an image showing the amount of light in a reflective mirror and a detector according to one embodiment of the present invention. More specifically, Figure 5a shows the amount of light incident on the reflective mirror, and Figure 5b shows the amount of light incident on the detector. For reference, the amount of light captured in the curved mirror is 93.1%.

[0054] Referring to Fig. 5, in the reverse photoelectron spectroscopy device of the present invention, it can be confirmed that the photons emitted from the sample exhibit a light collection efficiency of about 93.1% by the curved mirror. In addition, it can be confirmed that the photons reflected from the curved mirror are incident on the reflective mirror with a light quantity of about 93.0%, and it can be confirmed that the photons reflected from the reflective mirror are incident on the detector with a light quantity of about 92.7%.

[0055] That is, according to the reverse photoelectron spectroscopy device of the present invention, photons collected by the curved mirror can be incident on the reflective mirror with almost no loss, and photons reflected by the reflective mirror can also reach the final detector with minimal loss. In this way, the reverse photoelectron spectroscopy device of the present invention can exhibit the effect of increasing the photon detection efficiency of the detector by minimizing the loss of photons.

[0056] <Reverse photoelectron spectroscopy method>

[0057] In addition, the present invention discloses a reverse photoelectron spectroscopy method as a means for achieving the above-described purpose.

[0058] The reverse photoelectron spectroscopy method of the present invention comprises the steps of: irradiating a sample with electrons through a curved mirror; capturing and reflecting photons emitted from the sample irradiated with the electrons by the curved mirror; reflecting the reflected photons by a reflecting mirror; and detecting the reflected photons by a detector.

[0059] As previously described, the step of irradiating the sample with electrons can irradiate high-resolution, low-energy electrons via an electron beam while minimizing the impact on organic materials. Furthermore, the electrons irradiated onto the sample may be focused using a focusing lens (not shown) included in the electron beam. The focusing lens can act as a filter from an electron energy perspective by blocking electrons with energies lower than -0.9 V0.

[0060] In the step of capturing and reflecting photons emitted from the sample by a curved mirror, the curved mirror may include a reflective surface formed in a curved shape to increase the photon capturing capability as described above. The photons emitted by the electron-irradiated sample may be captured by the reflective surface of the curved mirror, and the curved mirror may reflect the photons so that the photons are focused toward a focus.

[0061] In the step of reflecting the reflected photons with a reflective mirror, the reflective mirror can be installed in the path of the photons reflected from the curved mirror as described above to reflect the reflected photons.

[0062] Photons reflected through the above reflective mirror can reach the detector and be finally detected.

[0063] The inverse photoelectron spectroscopy device of the present invention can minimize the optical path as the optical system is configured inside a single vacuum chamber.

[0064] In addition, the inverse photoelectron spectroscopy device of the present invention can improve spectral performance by reducing interference with photons in the air and reducing the degree of exposure to the external environment.

[0065] In addition, the inverse photoelectron spectroscopy device of the present invention can ensure convenience for users as it can be integrated into a single vacuum chamber.

[0066] The above description is merely an example of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present invention.

[0067] Accordingly, the embodiments disclosed in the present invention are intended to illustrate, rather than limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical concepts within the scope equivalent thereto should be construed as being included within the scope of the present invention.

[0068] <Explanation of symbols>

[0069] 110 support

[0070] 120 electron gun

[0071] 130 Curved Mirror

[0072] 140 reflective mirror

[0073] 150 detectors

[0074] 160 vacuum chamber

Claims

1. A support for supporting the sample; An electron gun for irradiating electrons onto the above sample; A curved mirror positioned on top of the sample to capture and reflect photons emitted from the sample; A reflective mirror that receives and reflects photons reflected from the above curved mirror; and A detector for detecting the reflected photon; An inverse photoelectron spectroscopy device, wherein the support, the electron gun, the curved mirror, the reflecting mirror and the detector are provided within a single vacuum chamber.

2. In paragraph 1, The above curved mirror is a reverse photoelectron spectroscopy device that reflects photons emitted from the sample and focuses them at a focus.

3. In paragraph 1, A reverse photoelectron spectroscopy device in which the above reflecting mirror is arranged parallel to and spaced apart from the curved mirror and reflects photons reflected from the curved mirror so that they are incident on the detector.

4. In paragraph 1, A reverse photoelectron spectroscopy device, wherein the detectors are arranged parallel to the electron gun at regular intervals.

5. In paragraph 1, The above curved mirror has a through hole through which electrons irradiated on the sample pass; and A reflective surface formed into a curve to surround the sample and reflect photons emitted from the sample by the electrons passing through the sample; A reverse photoelectron spectroscopy device, wherein the above through hole is formed on the above reflective surface.

6. In paragraph 5, The above-mentioned penetration hole is a reverse photoelectron spectroscopy device, wherein the diameter of the surface on which the electrons are incident is equal to or larger than the diameter of the reflective surface.

7. In paragraph 5, A reverse photoelectron spectroscopy device, wherein the diameter shape of the above through hole is formed into any one of a circular, elliptical, triangular, square, rectangular, polygonal and slit shape.

8. A step of irradiating electrons onto the sample through a curved mirror; A step of capturing and reflecting photons emitted from the sample irradiated with the electrons using a curved mirror; a step of reflecting the reflected photons with a reflective mirror; and A reverse photoelectron spectroscopy method, comprising: a step of detecting the reflected photon using a detector.

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