阅读说明：本技术 一种高压光谱椭偏测量装置及测量方法 (High-voltage spectrum ellipsometry measuring device and measuring method ) 是由 江浩 刘佳敏 王勐 刘世元 王一帆 谷洪刚 于 2020-05-28 设计创作，主要内容包括：本发明属于光学测量相关技术领域,并公开了一种高压光谱椭偏测量装置及测量方法。该装置包括入射起偏光路、反射检偏光路和装夹单元,入射起偏光路中设置有第一微透镜,用于将直径为毫米级的平行光束汇聚成直径为微米级的光斑并照射在待测样品表面；反射检偏光路中设置有第二微透镜,用于将装夹单元中待测样品表面反射的光线准直为平行反射光；装夹单元中设置有高压加载模块,该高压加载模块中包括相对设置的金刚石压砧,测量过程中,待测样品装夹在相对设置的金刚石压砧之间,通过金刚石压砧在待测样品上施加不同的压力,改变待测样品的受力状态,以此改变反射光的偏振态信息。通过本发明,实现待测样品压强依赖性光学常数的准确获取。(The invention belongs to the technical field related to optical measurement, and discloses a high-pressure spectrum ellipsometry measuring device and a measuring method. The device comprises an incident polarization light path, a reflection polarization detection light path and a clamping unit, wherein a first micro lens is arranged in the incident polarization light path and is used for converging parallel light beams with the diameter of millimeter level into light spots with the diameter of micron level and irradiating the light spots on the surface of a sample to be measured; a second micro lens is arranged in the reflection polarization detection light path and is used for collimating the light reflected by the surface of the sample to be detected in the clamping unit into parallel reflected light; the clamping unit is internally provided with a high-pressure loading module which comprises oppositely arranged diamond anvils, in the measuring process, a sample to be measured is clamped between the oppositely arranged diamond anvils, different pressures are applied to the sample to be measured through the diamond anvils, the stress state of the sample to be measured is changed, and therefore the polarization state information of reflected light is changed. By the method, the pressure-dependent optical constant of the sample to be measured can be accurately obtained.)

1. The utility model provides a high-pressure spectrum ellipsometry measuring device which characterized in that, the device includes incident polarizing path, reflection polarization-analyzing path and clamping unit, wherein:

the incident polarization light path is used for emitting elliptical polarized light and converging the elliptical polarized light into light spots to irradiate the surface of the sample to be measured of the clamping unit; the reflection polarization detection light path is used for detecting the polarized light reflected by the sample to be detected so as to obtain the polarization state information of the reflected light;

the incident polarization light path is provided with a first micro lens (60) which is used for converging the parallel light beams in the incident polarization light path into light spots and irradiating the light spots on the surface of a sample to be measured; a second micro lens (80) is arranged in the reflection polarization analyzing light path and is used for collimating light rays reflected by the surface of a sample to be detected in the clamping unit into parallel reflected light, and the second micro lens and the first micro lens are symmetrically arranged above the clamping unit;

the clamping unit is internally provided with a high-pressure loading module which comprises oppositely arranged diamond anvils (73), in the measuring process, a sample to be measured is clamped between the oppositely arranged diamond anvils, different pressures are applied to the sample to be measured through the diamond anvils, the stress state of the sample to be measured is changed, the polarization state information of the reflected light is changed, and the optical characteristics of the sample to be measured under different pressures are further obtained.

2. The high-pressure spectroscopic ellipsometry apparatus of claim 1, wherein the diamond anvil (73) is transparent, the size of the pressure-bearing surface of the diamond anvil is 100-200 μm, the diameter of the incident light spot on the surface of the sample to be measured is 30-60 μm, and the diameter of the parallel light beam in the incident polarization light path is 4-6 mm.

3. The high-voltage spectroscopic ellipsometry apparatus of claim 1, wherein the incident polarization light path comprises a light source (10), a collimating module (20), a polarizer (30) and a compensator (40), wherein the collimating module (20) is configured to collimate a divergent light beam emitted from the light source into a completely non-polarized parallel light beam, the polarizer (30) is configured to modulate the completely non-polarized parallel light beam into a linearly polarized light beam, and the compensator is configured to modulate the linearly polarized light beam into an elliptically polarized light with a polarization state varying with time.

4. The high-pressure spectroscopic ellipsometry apparatus of claim 3, wherein the collimating module (20) comprises a small converging lens (21), an aperture stop (22) and a small collimating lens (23), the small converging lens (21) is used for collecting the diverging light beam and converging it at the aperture stop (22), the aperture stop (22) is used for restricting the size of the converging light spot, and the small collimating lens (23) is used for collimating the converging light spot into a parallel light beam.

5. A high-pressure spectroscopic ellipsometry apparatus as in claim 3, wherein said compensator comprises a quarter wave plate (40) and a motor (50) for driving the wave plate in rotation.

6. The high-pressure spectroscopic ellipsometry apparatus of claim 1, wherein the reflection analyzer comprises a motor (50), a quarter-wave plate (40), an analyzer (90), a converging lens (100), and a detector (110), wherein the motor (50) drives the quarter-wave plate (40) to rotate to modulate the parallel reflected light from the second microlens (80), then the parallel reflected light is modulated by the analyzer (90), and finally the parallel reflected light is converged by the converging lens (100) into the detector, thereby detecting the polarization state information of the reflected light.

7. The method of measurement of a high-pressure spectroscopic ellipsometry apparatus of any one of claims 1-6, comprising the steps of:

s1, calibrating the diamond anvil to obtain the Mueller matrix M of the diamond anvil_d；

S2 placing a sample to be tested between diamond anvils which are oppositely arranged, applying pressure P to the sample to be tested through the diamond anvils, enabling the incident polarization light path to emit light to sequentially pass through the first micro lens, the diamond anvils, the sample to be tested, the diamond anvils and the second micro lens, and finally detecting through the reflection polarization detection light path to obtain a Mueller matrix M common to the sample to be tested and the diamond anvils under the pressure P₀；

S3 Mueller matrix M using the diamond anvil_dMueller matrix M shared by sample to be tested and diamond anvil cell under pressure P₀Is calculated to obtainObtaining the Mueller matrix M of the sample to be measured under the pressure P_s；

S4, changing the pressure P, and repeating the steps S2 and S3 to obtain the Mueller matrix of the sample to be measured under different pressures P, namely, the measurement of the sample to be measured is realized.

8. The measurement method of claim 7, wherein in step S1, the mueller matrix of the diamond anvil is obtained according to the following steps:

s11 Standard SiO₂The sample is placed between diamond anvils which are oppositely arranged, and the high-pressure spectrum ellipsometry measuring device is adopted to measure standard SiO₂Mueller matrix M of sample and diamond anvil cell₁；

S12 will be set at standard SiO₂Removing the diamond anvil above the sample, and measuring by using the high-pressure spectroscopic ellipsometry device to obtain SiO₂Mueller matrix M of the sample₂；

S13 SiO according to the standard₂Mueller matrix M of sample and diamond anvil cell₁And SiO₂Mueller matrix M of the sample₂And (3) calculating a Mueller matrix of the diamond anvil cell according to the following relational expression:

M_d＝(M₁·M₂)^1/2·M₂ ^-1

wherein M is_dIs a mueller matrix of a diamond anvil cell.

9. The method of claim 7, wherein in step S3, the Mueller matrix M of the sample to be tested is measured at a pressure P_sCalculated according to the following relation:

M₀＝M_d·M_s·M_d

wherein M is₀Is the common Mueller matrix of the sample to be tested and the diamond anvil cell.

Technical Field

The invention belongs to the technical field related to optical measurement, and particularly relates to a high-pressure spectrum ellipsometry measuring device and a measuring method.

Background

The spectroscopic ellipsometer is a standard measuring instrument capable of characterizing the optical constants of solid materials, and is widely applied to the acquisition of the optical constants of materials such as metals or alloys, semiconductors, dielectrics and the like as a nondestructive, non-contact and rapid measuring device. The basic measurement principle of the instrument is as follows: irradiating a beam of specific polarized light on the surface of a sample, decoupling an ellipsometric parameter or a muller matrix of the sample to be measured by capturing the light intensity of the reflected light and modulating, and then performing inversion fitting on the ellipsometric parameter or the muller matrix to obtain an optical constant of the sample to be measured.

With the development of high-pressure material physical theory research and application technology, the optical response characteristics of the material under the high-pressure loading condition are more and more concerned, and especially the optical constants of the material under the different pressure loading conditions can reflect the evolution characteristics of the crystal structure and the electronic energy band structure of the material along with the pressure. The existing methods for characterizing the high-pressure optical properties of materials mainly refer to high-pressure reflectivity measurement and high-pressure Stokes vector measurement, and when the method is used for measuring the pressure-dependent optical constants of the materials, obvious fitting errors are easily introduced, and the anisotropy of the materials caused by the pressure intensity is difficult to distinguish. In addition, the polarization effect of the diamond anvil is rarely considered in both high-pressure reflectivity measurement methods and high-pressure stokes vector measurement methods. Because the size of the pressure bearing surface of the diamond anvil is in the order of hundreds of microns, a common ellipsometer with measuring light spots in several millimeters cannot perform high-pressure ellipsometry parameter measurement.

Therefore, the present invention provides a measuring device and a measuring method capable of accurately characterizing the optical constant of a solid material under high pressure loading.

Disclosure of Invention

Aiming at the defects or the improvement requirements of the prior art, the invention provides a high-voltage spectrum ellipsometry measuring device and a measuring method, the device is used for researching and designing an optical constant measuring unit and a high-voltage loading module, calibrating the polarization effect of a diamond anvil under different pressure loading, further ensuring that the pressure dependence Mueller matrix of a sample to be measured can be accurately measured, and finally obtaining the pressure dependence optical constant of the sample to be measured by carrying out inversion fitting on the measured Mueller matrix. The measuring device realizes accurate characterization of the high-voltage optical constant of the solid material, realizes calibration of the polarization effect of the diamond anvil cell, and can carry out high-voltage optical property measurement research work on various solid materials. Meanwhile, the measuring device provided by the invention can be suitable for various samples to be measured, such as solid film materials, solid powder materials and the like, and has extremely strong expandability, such as the measuring spectral range and the loading pressure range can be adjusted according to actual research or application requirements.

To achieve the above object, according to one aspect of the present invention, there is provided a high-pressure spectroscopic ellipsometry apparatus including an incident polarization path, a reflection polarization analyzing path, and a clamping unit, wherein:

the incident polarization light path is used for emitting elliptical polarized light and converging the elliptical polarized light into light spots to irradiate the surface of the sample to be measured of the clamping unit; the reflection polarization detection light path is used for detecting the polarized light reflected by the sample to be detected so as to obtain the polarization state information of the reflected light;

the incident polarization light path is provided with a first micro lens which is used for converging the parallel light beams in the incident polarization light path into light spots and irradiating the light spots on the surface of a sample to be measured; a second micro lens is arranged in the reflection polarization detection light path and is used for collimating light rays reflected by the surface of a sample to be detected in the clamping unit into parallel reflected light, and the second micro lens and the first micro lens are symmetrically arranged above the clamping unit;

the clamping unit is internally provided with a high-pressure loading module which comprises oppositely arranged diamond anvils, a sample to be measured is clamped between the oppositely arranged diamond anvils in the measuring process, different pressures are applied to the sample to be measured through the diamond anvils, the stress state of the sample to be measured is changed, and therefore the polarization state information of the reflected light is changed.

Further preferably, the diamond anvil is transparent, the size of the pressure bearing surface of the diamond anvil is 100-200 microns, the diameter of an incident light spot on the surface of a sample to be measured is 30-60 microns, and the diameter of a parallel light beam in an incident polarization light path is 4-6 mm.

Further preferably, the incident polarization light path comprises a light source, a collimation module, a polarizer and a compensator, the collimation module is used for collimating a divergent light beam emitted by the light source into a completely non-polarized parallel light beam, the polarizer is used for modulating the completely non-polarized parallel light beam into a linearly polarized light beam, and the compensator is used for modulating the linearly polarized light beam into elliptically polarized light with a polarization state changing with time.

Further preferably, the collimating module comprises a small converging lens, an aperture stop and a small collimating lens, the small converging lens is used for collecting the diverging light beam and converging the diverging light beam at the aperture stop, the aperture stop is used for restricting the size of the converging light spot, and the small collimating lens is used for collimating the converging light spot into a parallel light beam.

Further preferably, the compensator includes a quarter wave plate and a motor driving the wave plate to rotate.

Further preferably, the reflection polarization analyzing optical path includes a motor, a quarter-wave plate, an analyzer, a converging lens and a detector, the motor drives the quarter-wave plate to rotate to modulate the parallel reflection light from the second microlens, then the parallel reflection light is modulated by the analyzer, and finally the parallel reflection light is converged into the detector by the converging lens, so as to detect the polarization state information of the reflection light.

According to another aspect of the present invention, there is provided a measuring method of the high-pressure spectroscopic ellipsometry apparatus, the measuring method comprising the steps of:

s1, calibrating the diamond anvil to obtain the Mueller matrix M of the diamond anvil_d；

S2 placing a sample to be tested between diamond anvils which are oppositely arranged, applying pressure P to the sample to be tested through the diamond anvils, enabling the incident polarization light path to emit light to sequentially pass through the first micro lens, the diamond anvils, the sample to be tested, the diamond anvils and the second micro lens, and finally detecting through the reflection polarization detection light path to obtain a Mueller matrix M common to the sample to be tested and the diamond anvils under the pressure P₀；

S3 Mueller matrix M using the diamond anvil_dMueller matrix M shared by sample to be tested and diamond anvil cell under pressure P₀Calculating to obtain the Mueller matrix M of the sample to be measured under the pressure P_s；

S4, changing the pressure P, and repeating the steps S2 and S3 to obtain the Mueller matrix of the sample to be measured under different pressures P, namely, the measurement of the sample to be measured is realized.

Further preferably, in step S1, the mueller matrix of the diamond anvil is obtained according to the following steps:

s11 Standard SiO₂The sample is placed between diamond anvils which are oppositely arranged, and the high-pressure spectrum ellipsometry measuring device is adopted to measure standard SiO₂Mueller matrix M of sample and diamond anvil cell₁；

S12 will be set at standard SiO₂Removing the diamond anvil above the sample, and measuring by using the high-pressure spectroscopic ellipsometry device to obtain SiO₂Mueller matrix M of the sample₂；

S13 SiO according to the standard₂Mueller matrix M of sample and diamond anvil cell₁And SiO₂Mueller matrix M of the sample₂And (3) calculating a Mueller matrix of the diamond anvil cell according to the following relational expression:

M_d＝(M₁·M₂)^1/2·M₂ ^-1

wherein M is_dIs a mueller matrix of a diamond anvil cell.

Further preferably, in step S3, the mueller matrix M of the sample to be tested is under pressure P_sCalculated according to the following relation:

M₀＝M_d·M_s·M_d

wherein M is₀Is the common Mueller matrix of the sample to be tested and the diamond anvil cell.

In general, compared with the prior art, the above technical solution conceived by the present invention has the following effects:

1. the size of the pressure bearing surface of the diamond anvil is in the order of hundreds of microns, so that the external pressure can be effectively transmitted to the surface of a sample, the external pressure can be amplified, the surface pressure of the sample can easily reach the GPa order, and meanwhile, the diamond anvil can allow the transmission of light beams, so that the detection light beams can reach the surface of the sample;

2. the diameter of the incident light spot is 30-60 microns, so that the incident light spot can completely irradiate the diamond anvil surface with the pressure bearing surface size of 100-200 microns, reflection generated by irradiation to other places is avoided, measurement errors are brought, and the measurement precision is improved in the mode;

3. the high-voltage spectrum ellipsometry measuring device and the measuring method provided by the invention not only realize the Mueller matrix of the sample to be measured under different pressure loading conditions, can obtain the optical constant of the sample to be measured by fitting the Mueller matrix, but also realize the calibration of the polarization effect of the diamond anvil cell, thereby ensuring the accurate measurement of the pressure-dependent optical constant of any sample. In fact, the present invention is able to identify the birefringence characteristics of solid materials caused by pressure.

Drawings

FIG. 1 is a schematic diagram of a high-pressure spectroscopic ellipsometry apparatus constructed in accordance with a preferred embodiment of the present invention.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:

10-light source, 20-collimation module, 21-small convergent lens, 22-aperture diaphragm, 23-small collimation lens, 30-polarizer, 40-quarter wave plate, 50-motor, 60-first micro lens, 71-diamond saddle, 72-sample to be measured, 73-diamond anvil, 80-second micro lens, 90-analyzer, 100-convergent lens and 110-optical detector.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

As shown in FIG. 1, the high-pressure spectroscopic ellipsometry device for calibrating the polarization effect of a diamond anvil and determining the optical constants of a sample under a high-pressure loading condition comprises an optical constant measuring unit and a clamping unit.

(1) The clamping unit is internally provided with a high-pressure loading module which comprises a diamond saddle 71, a diamond anvil 73 and a sample 72 to be tested, wherein the diamond saddle 71 wraps a pair of diamond anvils 73 and applies external pressure to the diamond anvils 73, the diamond anvils 73 transmit the pressure to the sample 72 to be tested, and the pair of diamond anvils 73 and the sample 72 to be tested form a sandwich structure;

(2) the optical constant measuring module comprises an incident polarization light path and a reflection polarization analyzing light path, wherein the incident polarization light path comprises a white light source 10, a collimation module 20, a polarizer 30, a compensator and a first micro lens 60, the compensator comprises a motor 50 and a quarter wave plate 40, the collimation module comprises a small convergent lens 21, an aperture diaphragm 22 and a small collimating lens 23, and the reflection polarization analyzing light path comprises a second micro lens 80, a compensator, an analyzer 90, a convergent lens 100 and a light detector 110;

(3) the white light source 10 generates a divergent light source with a spectral range of 200 nm-1700 nm, and then the divergent light source is incident to the collimation module 20, the small convergent lens 21 firstly collects divergent light beams and converges the divergent light beams to the aperture diaphragm 22, and then the divergent light beams are collimated into parallel light beams by the small collimation lens 23, wherein the parallel light beams are completely unpolarized light beams;

(4) the completely unpolarized parallel light beam is modulated into a linearly polarized light beam by a polarizer 30, then is further modulated into an elliptically polarized light with a polarization state changing along with time and a diameter of 4-6 mm by a quarter-wave plate 40 driven by a motor 50 to rotate, and then is converged into a conical light beam with a diameter of 30-60 microns by a first micro lens 60, wherein the conical light beam penetrates through a diamond anvil 73 and is just focused on the surface of a pressure-bearing sample 72;

(5) the cone beam reflected by the surface of the sample 72 to be measured penetrates through the diamond anvil 73 again, is collimated into a parallel beam by the second micro lens 80, is modulated by the quarter wave plate 40 driven by the motor 50 to rotate, is then subjected to polarization modulation by the polarization detector 90, and is finally converged into the optical detector 110 by the converging lens 100, so that the measuring device collects a light intensity signal which changes along with time, and the measurement mueller matrix M contributed by the sample 72 to be measured and the diamond anvil 73 together can be obtained by performing modulation and demodulation in the form of fourier transform on the light intensity signal₀。

(6) The incident polarization path converges the polarized light beam with a specific polarization state on the diamond anvil 73, the converged probe light beam penetrates through the diamond anvil 73 and finally irradiates the surface of the sample 72, the reflection polarization analysis path collects the light beam reflected by the surface of the sample 72 and penetrating through the diamond anvil 73, and the polarization state of the reflected light beam is analyzed, so that a Mueller matrix M shared by the sample 72 to be measured and the diamond anvil 73 is obtained₀；

(7) When the diamond anvil 73 is pressed by the diamond saddle 71, the sample 72 is also subjected to a high pressure, and when the converged incident beam penetrates the diamond anvil 73, the diamond anvil 73 modulates the polarization state of the incident beam, and when the divergent beam reflected by the surface of the sample 72 passes through the diamond anvil 73 again, the diamond anvil 73 also modulates the polarization state of the reflected beam, which can be distinguished by assuming that the mueller matrices of the sample 72 and the diamond anvil 73 are M, respectively_sAnd M_dThen, the following formula M can be determined₀＝M_d·M_s·M_dThus, to determine the Mueller matrix M of the sample 72 to be tested_sThe Mueller matrix M of the diamond anvil 73 must be determined by a calibration method_d；

(8) The diamond anvil 73 is calibrated by measuring the standard SiO with the optical constant measuring module when the high-voltage loading module is not installed or installed₂Mueller matrix M of the sample₂And M₁By the formula M_d＝(M₁·M₂)^1/2·M₂ ^-1To calculate the Mueller matrix M of the diamond anvil 73_dMeanwhile, since the optical constants of the diamond anvil 73 hardly change within the range of the pressure to be studied, the mueller matrix of the diamond anvil 73 under the loading of other pressures is still M_d。

After the Mueller matrix of the diamond anvil 73 is determined in the step (8), the Mueller matrix of the sample 72 to be tested under the high-pressure loading condition can be determined by substituting the determined Mueller matrix into the formula in the step (7), and then the Mueller matrix M is subjected to_sAnd (5) carrying out inversion fitting to obtain the high-pressure-dependent optical constant of the sample 72 to be measured.

The optical constants of the solid samples of the other types were characterized under high pressure loading, almost identical to the above-described implementation, with no substantial difference.

It will be understood by those skilled in the art that the foregoing is merely a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included within the scope of the present invention.