CN108226574B - A Scanning Thermoelectric Microscopy Device for Thermoelectric Figure of Merit Behavioral Microscopic Imaging - Google Patents

Abstract

This application discloses a scanning thermoelectric microscopy device for microscopic imaging of thermoelectric figure of merit behavior, which is used to realize high-resolution microscopic imaging of the thermoelectric figure of merit behavior of a thermoelectric material sample under test, including: subsurface The thermoelectric signal in-situ excitation module is used for in-situ excitation of the subsurface thermoelectric Seebeck current signal of the measured thermoelectric material sample; the thermoelectric signal in-situ detection module is used for the subsurface thermoelectric Seebeck current signal of the measured thermoelectric material sample. In-situ real-time detection; pyroelectric signal microscopic imaging module, used for high-resolution microscopic imaging and display of subsurface pyroelectric figure of merit signals. This application has the unique functions of in-situ excitation of subsurface pyroelectric signals and in-situ synchronous characterization, and has the advantages of high resolution, high sensitivity, high signal-to-noise ratio, and direct testing. The key technical device of the application has simple structure and strong compatibility, is suitable for combining with different commercial scanning electron microscope systems, and is a new technology that is easy to popularize and apply.

Description

A Scanning Thermoelectric Microscopy Device for Thermoelectric Figure of Merit Behavioral Microscopic Imaging

technical field

The application relates to the field of signal detection instruments, in particular to a scanning pyroelectric microscopy device for pyroelectric figure of merit behavioral microscopic imaging.

Background technique

As an important energy material at present, thermoelectric materials based on the mutual conversion effect of heat energy and electric energy are used in many important high-tech industries such as the recycling of industrial waste heat and automobile exhaust heat, high-precision temperature control devices, space technology, military equipment, and information technology. It has a very broad application prospect in the field, which has attracted great attention from all over the world. For example, the United States has developed semiconductor thermoelectric materials to realize high-efficiency space power supplies that convert nuclear reaction heat energy into electrical energy, providing high-efficiency space power for its return to the moon and future manned Mars exploration programs. Reliable energy guarantee.

The thermoelectric figure of merit (also known as ZT factor) is the only index that expresses the performance of thermoelectric materials and the efficiency of thermoelectric conversion. The thermoelectric figure of merit is defined as:

ZT＝S ² σT/κ (1)

in,

S - Seebeck coefficient of thermoelectric materials

σ——conductivity

T - absolute temperature

κ - thermal conductivity

The determination of thermoelectric figure of merit is usually to measure parameters such as electrical conductivity, Seebeck coefficient and thermal conductivity respectively, and then determine the thermoelectric figure of merit of the measured material according to the definition of ZT factor. So far, there is no high-resolution microscopic imaging technology that can realize the spatial distribution of thermoelectric figure of merit. Therefore, it is difficult to intuitively understand and reveal the dynamic law of thermoelectric transport in micro-regions. In order to develop thermoelectric materials with high thermoelectric conversion efficiency, it is urgent to develop new characterization techniques to achieve an in-depth understanding of the structure-activity relationship between thermoelectric microstructures and thermoelectric transport behavior, especially those that can realize the thermoelectric figure of merit behavior of thermoelectric materials and devices. Characterization technology of high-resolution microscopic imaging to promote independent innovation research and development of high performance, high conversion efficiency, new thermoelectric materials and devices.

Contents of the invention

Based on the urgent need for research on the thermoelectric transport properties of subsurface thermoelectric materials and thermoelectric devices, this application proposes a new method for high-resolution microscopic imaging of subsurface thermoelectric figure of merit behavior on the ordinary scanning electron microscope platform, and establishes The scanning thermoelectric microscope with electron beam modulation has realized the in-situ, non-destructive high-resolution microscopic imaging of the internal thermoelectric behavior of thermoelectric materials and thermoelectric devices, and provided a high-resolution in-situ characterization technology for the evaluation of the physical properties of thermoelectric materials and thermoelectric devices.

The present application discloses a scanning thermoelectric microscopy device for microscopic imaging of thermoelectric figure of merit behavior, which is used to realize high-resolution microscopic imaging of the thermoelectric figure of merit behavior of a subsurface thermoelectric material sample, characterized in that, The device further includes: a subsurface thermoelectric signal in situ excitation module, which is used to in situ excite the subsurface thermoelectric Seebeck current signal of the measured thermoelectric material sample;

The thermoelectric signal in-situ detection module is used for in-situ real-time detection of the subsurface thermoelectric Seebeck current signal of the measured thermoelectric material sample;

Thermoelectric signal microscopic imaging module, used for high-resolution microscopic imaging and display of subsurface thermoelectric figure of merit signal;

Wherein, the relationship between the subsurface thermoelectric Seebeck current signal of the thermoelectric material sample and the thermoelectric figure of merit is:

Wherein, the I _2ω is the Seebeck current of the nonlinear 2ω, and Π, ZT, ι, P are the Peltier coefficient of the thermoelectric material, the thermoelectric figure of merit, the nonlinear beam current characteristic relaxation time and the heat of electron kinetic energy conversion Power density, the magnitude of the nonlinear 2ω Seebeck current I _2ω reflects the distribution inhomogeneity of the micro-region thermoelectric figure of merit behavior of the tested material sample.

Preferably, the present invention further discloses a scanning thermoelectric microscopy device for thermoelectric figure-of-merit behavioral microscopic imaging, characterized in that the subsurface thermoelectric signal in-situ excitation module further includes:

An electron gun, an electron beam deflector, a signal generator, a scanning electron microscope lens barrel, a scanning electron microscope sample chamber and a pyroelectric signal detector, the signal generator controls the electron beam deflector, from the The electron beam emitted by the electron gun passes through the electron beam deflector, enters the scanning electron microscope lens barrel, and then enters the measured thermoelectric material sample on the scanning electron microscope sample chamber, and the thermoelectric signal detector is used for the original bit detection of the weak subsurface thermoelectric current signal generated by the interaction between the measured thermoelectric material sample and the periodically modulated electron beam.

Preferably, the present invention further discloses a scanning thermoelectric microscopy device for thermoelectric figure-of-merit behavioral microscopic imaging, characterized in that, the scanning electron microscope barrel includes: a first condenser, a second condenser, a scanning coil and objective lens.

Preferably, the present invention further discloses a scanning pyroelectric microscopy device for pyroelectric figure of merit behavioral microscopic imaging, characterized in that the pyroelectric signal detector further includes:

A detector upper cover, a metal gasket, an insulator, a detector housing, a signal output end, and a positioning end, the detector upper cover is arranged on the measured thermoelectric material sample, and the measured thermoelectric material The bottom of the material sample is sequentially provided with the metal gasket, the insulator, the detector housing and the positioning end, and the signal output end is connected to the bottom of the metal gasket for effectively outputting the thermoelectric signal.

Preferably, the present invention further discloses a scanning thermoelectric microscopy device for thermoelectric figure of merit behavioral microscopic imaging, characterized in that,

The subsurface pyroelectric signal in-situ detection module further includes: a preamplifier and a lock-in amplifier, wherein the signal terminal of the pyroelectric signal detector, the preamplifier and the lock-in amplifier are connected in sequence to realize In situ detection and processing of the nonlinear 2ω Seebeck current I _2ω .

Preferably, the present invention further discloses a scanning thermoelectric microscopy device for thermoelectric figure-of-merit behavior microscopic imaging, characterized in that the subsurface thermoelectric signal microscopic imaging module further includes: a scanning electron microscope control The system and a computer system are used to realize in-situ real-time processing of subsurface pyroelectric signals and display high-resolution microscopic imaging results.

Preferably, the present invention further discloses a scanning thermoelectric microscopy device for thermoelectric figure-of-merit behavioral microscopic imaging, characterized in that the electron beam deflector is placed in the first stage of the scanning electron microscope barrel between the aperture and the second aperture.

Preferably, the present invention further discloses a scanning thermoelectric microscopy device for thermoelectric figure-of-merit behavioral microscopic imaging, characterized in that the electron beam deflector is composed of a pair of parallel metal plates, one end of which is grounded, The other end is connected to the output end of the signal generator, and the distance between the parallel metal plates is between 3 mm and 10 mm.

Preferably, the present invention further discloses a scanning thermoelectric microscopy device for thermoelectric figure-of-merit behavioral microscopic imaging, characterized in that the amplitude range of the alternating excitation voltage at both ends of the electron beam deflector is 30V-100V . The working frequency range is 1kHz-200kHz, which is used to realize the periodic modulation of the electron beam.

The present application provides a device that can be used for high-resolution microscopic imaging of thermoelectric materials and internal thermoelectric behaviors of thermoelectric devices. Combining multiple physical effects such as scanning electron microscope imaging function, thermal wave effect of periodically modulated electron beam and thermoelectric material interaction, Joule heating effect, thermoelectric Seebeck effect, thermoelectric Peltier effect, so as to establish its effective in situ excitation Subsurface pyroelectric signals of thermoelectric materials and thermoelectric devices, and electron beam modulation scanning thermoelectric microscopy for high-resolution thermoelectric microscopic imaging. This application not only has the unique functions of in-situ simultaneous excitation of subsurface thermoelectric signals and in-situ synchronous characterization, but also has the advantages of high resolution, high sensitivity, high signal-to-noise ratio, and direct testing. The key technical device described in this application has simple structure and strong compatibility, and is suitable for combining with different commercial scanning electron microscope systems, and is a new technology that is easy to popularize and apply.

Electron beam modulation scanning thermoelectric microscope expands the evaluation function of thermoelectric material and thermoelectric device subsurface thermoelectric physical properties that the existing commercial scanning electron microscope does not have, and provides a basis for in-depth study of thermoelectric transport theory of thermoelectric materials and innovative research and development of thermoelectric materials and their devices An important new solution for in situ, high-resolution characterization.

Description of drawings

The above and other objects, features and advantages of the present application will be apparent to those skilled in the art from the detailed description of the present application below with reference to the accompanying drawings.

Fig. 1 schematically shows the schematic diagram of the electron beam modulation scanning thermoelectric microscope of the subsurface thermoelectric behavior microscopic imaging technology of the present application;

Fig. 2 (a) is the periodic square wave modulated electron beam waveform diagram;

Figure 2(b) is a schematic diagram of the in-situ excitation of the nonlinear beam through the interaction between the periodically modulated electron beam and the thermoelectric material;

Fig. 3 schematically shows the structural block diagram of the subsurface thermoelectric behavior microscopic imaging device of the present application;

Fig. 4 schematically shows the structural block diagram of scanning electron microscope barrel main body described in Fig. 3;

Fig. 5 schematically shows the structural block diagram of subsurface pyroelectric signal detector described in Fig. 3;

Figure 6 schematically shows the high-resolution imaging results of the subsurface thermoelectric behavior of CoSb ₃ thermoelectric materials;

Fig. 7 schematically shows the high-resolution imaging results of the subsurface thermoelectric behavior of Bi ₂ Te ₃ thermoelectric devices.

reference sign

11 - electron gun

12——Electron beam deflector

13——Scanning Electron Microscope Tube

14——Scanning Electron Microscope Sample Room

15——Pyroelectric signal detector

16 - Preamplifier

17 - Lock-in amplifier

18——Scanning Electron Microscope Control System

19 - Computer systems

20 - signal generator

131——First Condenser

132——Second condenser lens

133 - scanning coil

134 - objective lens

14——Scanning electron microscope sample room

151——Tested thermoelectric material sample

152 - metal washer

153——Detector cover

154——Detector housing

155——signal output port

156 - insulator

157——Positioning end

100——Subsurface pyroelectric signal in-situ excitation module

200——In-situ detection module of subsurface pyroelectric signal

300——Subsurface pyroelectric signal in situ imaging module

Detailed ways

The following examples are the results of imaging the subsurface thermoelectric behavior of thermoelectric materials and thermoelectric devices using the electron beam modulation scanning thermoelectric microscope of the present application to further illustrate the effect of the present application, but are not limited to the following examples.

The present application establishes a new method and device for microscopic imaging of thermoelectric behavior on the subsurface of thermoelectric materials.

The relevant working principle of this application is shown in Figure 1, and can be specifically expressed as follows:

Step S1, when the scanning electron microscope electron beam is periodically modulated by an alternating voltage with frequency ω;

In step S2, a periodic heat wave with frequency ω will be formed inside the thermoelectric material sample;

Step S3, due to the thermoelectric Seebeck effect of the thermoelectric material, thermoelectric Peltier effect and other unique physical effects, the interaction between the periodic thermal wave and the thermoelectric material will generate a non-linear 2ω Seebeck current;

Step S4, according to the spectral relationship of the thermal wave, the penetration depth of the thermal wave is determined by the modulation frequency of the thermal wave. The higher the frequency, the shallower the penetration depth of the thermal wave; on the contrary, the deeper the penetration depth of the thermal wave. Therefore, the thermoelectric effect excited by the thermal wave at different frequencies can reflect the thermoelectric response behavior at different depths inside the thermoelectric material;

In step S5, according to the thermoelectric effect and the spectrum relationship, high-resolution microscopic imaging of the thermoelectric behavior inside the thermoelectric material micro-domain (ie subsurface) can be realized by in-situ detection of the 2ω Seebeck current at different frequencies.

Figure 2(a) and (b) show the schematic diagrams of periodically square-wave modulated electron beam and its in-situ excited nonlinear beam.

Theoretical analysis shows that this 2ω-current is directly related to the thermoelectric figure of merit (ZT). The theoretical analysis is detailed as follows:

Figure 2(a) is a waveform diagram of a periodically modulated electron beam, and Figure 2(b) is a schematic diagram of the in-situ excitation of a nonlinear beam current for the interaction between a periodically modulated electron beam and a thermoelectric material, and the interaction between a periodic electron beam and a thermoelectric material Multiple physical effects will be produced, including Joule heating effect, Seebeck effect, Peltier effect and so on. As shown in Figure 2(b), according to the principle of heat transfer, the general heat conduction equation of thermoelectric micro-area can be written as follows:

In formula (2),

c - the heat capacity of the thermoelectric sample

ρ——The density of the thermoelectric sample

σ——conductivity

Π——Peltier coefficient

λ——thermal conductivity

Among them, T(t) and Represents the dynamic distribution of temperature and potential. The first item on the right side of the formula is the heat flux generated by the Peltier effect, the second item is the heat flux generated by the temperature gradient, the third item is the power density generated by the Joule heating effect, and the fourth item p represents the thermal power density of electron kinetic energy conversion. The temperature gradient excites the Seebeck effect, and the Seebeck effect relationship can be given by the following expression:

Combining the basic relationship between heat and thermoelectricity:

cρa=λ (4)

And the relationship between current, electric field and potential in the hemispherical thermoelectric interaction zone with radius r, the function expression of nonlinear current can be solved as follows:

After Fourier series expansion, the amplitude of its double frequency harmonic signal can be expressed as:

in,

Π——Peltier coefficient of thermoelectric material

ZT——Thermoelectric figure of merit

τ——Nonlinear beam characteristic relaxation time

P——thermal power density of electron kinetic energy conversion

It can be seen from the above formula that at a certain frequency, since other parameters are constant, the 2ω-current signal mainly reflects the value of the thermoelectric figure of merit ZT of the thermoelectric material, and the larger 2ω-current signal reflects the larger value of ZT in the material. High thermoelectric figure of merit characteristics.

On the other hand, according to the spectral relationship of thermal waves, the penetration depth of thermal waves is determined by the modulation frequency of thermal waves. The higher the frequency, the shallower the penetration depth of the heat wave; on the contrary, the deeper the penetration depth of the heat wave. Therefore, the thermoelectric effect excited by thermal waves at different frequencies can reflect the thermoelectric response behavior at different depths inside the thermoelectric material. Therefore, in situ detection of 2ω Seebeck currents at different frequencies can realize high-resolution microscopic imaging of the thermoelectric behavior inside the micro-domain (ie subsurface) of thermoelectric materials.

Based on this working principle, this application establishes a high-resolution microscopic imaging device based on the scanning electron microscope's subsurface thermoelectric behavior—electron beam modulation scanning thermoelectric microscope

Please refer to FIG. 3 for a structural block diagram of the subsurface thermoelectric behavior microscopic imaging device of the present application.

It consists of three parts: an in-situ excitation module 100 for subsurface pyroelectric signals, an in-situ detection module 200 for pyroelectric signals, and a microscopic imaging module 300 for pyroelectric signals.

Among them, the subsurface thermoelectric signal in-situ excitation module 100 is used to excite the subsurface thermoelectric Seebeck current signal of the thermoelectric material in situ; the subsurface thermoelectric signal in-situ detection module 200 is used to realize the subsurface thermoelectric Seebeck current signal of the thermoelectric material. In-situ real-time detection and processing; pyroelectric signal microscopic imaging module 300, used to realize high-resolution microscopic imaging of subsurface pyroelectric signals and display the results.

Wherein, subsurface pyroelectric signal in-situ excitation module 100 includes: an electron gun 11, an electron beam deflector 12, a scanning electron microscope barrel 13, a scanning electron microscope sample chamber 14, a pyroelectric signal detector 15, a signal generation device 20. The electron gun 11 , electron beam deflector 12 , scanning electron microscope barrel 13 , scanning electron microscope sample chamber 14 , and pyroelectric signal detector 15 are connected in sequence, wherein the signal output terminal of the signal generator 20 is connected to the electron beam deflector 12 .

Among them, the electron beam deflector 12 is composed of two parallel metal pole plates, which are placed between the first-level diaphragm and the second-level diaphragm in the scanning electron microscope lens barrel 13, and the distance between the two parallel metal pole plates is 3 mm to 10 mm. Between them, an alternating excitation voltage is applied to both ends, the signal amplitude ranges from 30V to 100V, and the operating frequency range is 1kHz to 200kHz. Thus, through the alternating voltage on the two parallel metal plates of the electron beam deflector 12, The periodic modulation of the electron beam emitted by the electron gun 11 of the scanning electron microscope is realized.

FIG. 4 further illustrates the composition of the scanning electron microscope lens barrel 13 therein.

It includes: a first condenser lens 131, a second condenser lens 132, a scanning coil 133 and an objective lens 134, constituting the main structure of the lens barrel of the scanning electron microscope.

FIG. 5 further illustrates the composition of the pyroelectric signal detector 15 .

Including: the measured thermoelectric material sample 151, the metal gasket 152, the detector cover 153, the detector housing 154, the signal output terminal 155, the insulator 156, the positioning terminal 157; the detector cover 153, the measured thermoelectric material sample 151 , the metal washer 152, the insulator 156, the detector housing 154, and the positioning end are connected in sequence; the signal output end 155 is connected to the bottom of the metal washer 152 for effective output of thermoelectric signals. The pyroelectric signal detector 15 is placed on the sample chamber 14 of the scanning electron microscope and connected through the positioning end 157 . The pyroelectric signal detector 15 is an important component for the in-situ excitation of the subsurface pyroelectric signal, and its function is to interact with the periodically modulated electron beam between the measured thermoelectric material sample 151 and in situ excite the internal thermoelectric transport of the measured thermoelectric material sample 151. Informative and extremely weak subsurface pyroelectric signals. At this time, the measured thermoelectric material sample 151 and the periodically modulated electron beam produce multiple physical effects such as the Joule heating effect, the thermoelectric Seebeck effect, and the thermoelectric Peltier effect, thereby effectively in-situ exciting and the internal thermoelectric transport of the measured thermoelectric material sample 151. Closely correlated double-frequency nonlinear thermoelectric Seebeck current signals.

Both the upper cover 153 of the pyroelectric signal detector and the housing 154 of the detector are connected by fine-pitch threads to facilitate the installation of samples of different sizes and make them in good contact. The detector components are all made of metal materials, assembled and connected to form a shielding body to effectively prevent interference from external stray signals.

In FIG. 5 , the signal output terminal 155 is connected to the bottom of the metal washer 152 through a cable, so as to realize the effective output of the subsurface thermoelectric signal.

The positioning end 157 of the pyroelectric signal detector is connected to the components of the scanning electron microscope sample chamber 14 to realize the scanning of the measured thermoelectric material sample 151 by the periodically modulated electron beam and the excitation of subsurface pyroelectric signals.

The signal generator 20 in Figure 2 applies a frequency-modulated alternating voltage to the electron beam deflector 12, thereby realizing periodic modulation of the electron beam emitted by the electron gun, and the frequency-modulated electron beam is incident through the main body 13 of the scanning electron microscope barrel On the measured thermoelectric material sample 151 of the thermoelectric signal detector 15 on the scanning electron microscope sample chamber 14; the periodically modulated electron beam periodically scans the measured thermoelectric material sample 151, thereby generating periodic heat inside the thermoelectric sample Wave, and then due to the thermoelectric Seebeck effect and Peltier effect, a nonlinear double-frequency thermoelectric Seebeck current signal is generated inside the thermoelectric material. The current signal is output through the signal output terminal 155 at the bottom of the metal gasket 152 closely connected with the thermoelectric sample 151 .

The subsurface pyroelectric signal in-situ detection module 200 includes: a preamplifier 16 and a lock-in amplifier 17 . One end of the preamplifier 16 is connected to the signal output end 155 of the pyroelectric signal detector 15 , and the other end is connected to the input end of the preamplifier 16 . The output end of the preamplifier 16 is connected to the signal input end of the lock-in amplifier 17 , and the reference signal end of the lock-in amplifier 17 is connected to the synchronous signal port of the signal generator 20 . The high-sensitivity preamplifier 16 and the lock-in amplifier 17 together constitute the in-situ detection module 200 of the subsurface pyroelectric signal, which has the advantages of high measurement sensitivity, strong anti-interference, linear and nonlinear detection functions, and meets the working requirements of the system. Realize high-sensitivity detection of weak pyroelectric signals.

The subsurface thermoelectric signal in situ imaging module 300 includes: a scanning electron microscope control system 18 and a computer system 19 . The signal output terminal of the lock-in amplifier 17 outputs a nonlinear 2ω Seebeck current signal to the scanning electron microscope control system 18 and computer system 19 to realize in-situ real-time processing and imaging of subsurface pyroelectric signals, and display high-resolution imaging results.

Example 1

Using the high-resolution microscopic imaging device for subsurface thermoelectric signals established in this application, the electron beam modulation scanning thermoelectric microscope, was used to test the subsurface thermoelectric behavior of thermoelectric materials and devices, and the results are shown in Figure 6 and Figure 7 .

Figure 6 shows the thermoelectric microscopic imaging results of a Bi ₂ Te ₃ bulk thermoelectric material at different frequencies, where picture (a) is the secondary electron image of the sample surface topography, and picture (bi) is twice the size of the sample Frequency thermoelectric Seebeck current like. It can be seen from the figure that the thermoelectric Seebeck current image shows completely different information from the topographic image in figure (a). It is closely related to the strong scattering of thermoelectric transport carriers. The thermoelectric microscopic images of different frequencies reflect the thermoelectric defect structure with different penetration depths of modulated electron beams. As the modulation frequency decreases, the penetration depth gradually increases, and the outlines of internal defect particles gradually appear and become clearer, showing different depths. Effects of defects on thermoelectric transport behavior.

Example 2

Fig. 7(a) is the result of thermoelectric microscopic imaging of a Bi ₂ Te ₃ bulk thermoelectric device, in which (a) is the secondary electron image of the surface topography of the thermoelectric device, showing the thermoelectric material and metal electrodes on the surface of the device. Figure (b) is the thermoelectric microscopic image of the boxed area in Figure (a). It can be clearly seen in the figure that the thermoelectric material shows thermoelectric contrast information, but the metal electrode part of the device does not, so it is sufficient It is shown that the scanning thermoelectric microscopy contrast of electron beam modulation is only derived from the pyroelectric effect. The complex thermoelectric contrast image of the thermoelectric material in Figure (b) reflects the interaction behavior of the thermoelectric transport carriers in the micro-area of the thermoelectric material and the microstructures such as grains, grain boundaries, and defects in the micro-area, and reflects the thermoelectric figure of merit inside the thermoelectric device. The inhomogeneity of the factor also reflects the spatial inhomogeneity of thermoelectric transport.

The above examples show that the electron beam modulation scanning thermoelectric microscopy device based on the scanning electron microscope solves the key technical problem of high-resolution microscopic imaging of thermoelectric material and subsurface thermoelectric figure of merit behavior inside the device. The new microscopic imaging device realizes in-situ excitation and in-situ detection of thermoelectric behavior inside materials and devices, and expands the function of high-resolution microscopic imaging of subsurface thermoelectric behavior that existing commercial scanning electron microscopes do not have. The nature of the correlation between thermoelectric microstructure and thermoelectric transport inside thermoelectric materials and thermoelectric devices, especially the dynamic behavior of subsurface thermoelectric transport provides an important new method for in situ characterization.

In summary, the outstanding advantages of this application combine the scanning electron microscope imaging function, electron beam modulation technology, the thermal wave effect of the interaction between modulated electron beam and materials, and the Seebeck effect and Peltier effect of thermoelectric materials to develop subsurface A new method for characterization of thermoelectric behavior, established scanning thermoelectric microscopy imaging based on electron beam modulation of scanning electron microscope, to realize high-resolution microscopic imaging of thermoelectric transport behavior of thermoelectric materials and thermoelectric device subsurfaces.

This application has the unique functions of in-situ excitation of subsurface pyroelectric signals and in-situ synchronous characterization, and has the advantages of high resolution, high sensitivity, high signal-to-noise ratio, and direct testing. The key technical device described in this application has simple structure and strong compatibility, and is suitable for combining with different commercial scanning electron microscope systems. important applications in other fields.

The foregoing description of the preferred embodiment is provided to enable any person skilled in the art to make or utilize the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles described herein can be applied to other embodiments without the use of inventive step. Thus, the present application will not be limited to the embodiments shown here, but should be based on the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. A scanning thermoelectric microscopy apparatus for thermoelectric figure of merit behavior microscopy imaging for achieving high resolution microscopy imaging of sub-surface thermoelectric figure of merit behavior of a thermoelectric material sample under test, the apparatus further comprising:

the subsurface thermoelectric signal in-situ excitation module is used for in-situ exciting a subsurface thermoelectric seebeck current signal of the tested thermoelectric material sample;

the thermoelectric signal in-situ detection module is used for carrying out in-situ real-time detection on the subsurface thermoelectric seebeck current signal of the tested thermoelectric material sample;

the thermoelectric signal microscopic imaging module is used for performing high-resolution microscopic imaging and displaying on the sub-surface thermoelectric figure of merit factor signals;

wherein the relationship between the sub-surface thermoelectric seebeck current signal of the thermoelectric material sample and the thermoelectric figure of merit factor is as follows:

wherein, the I_2ωThe current is a nonlinear 2 omega Seebeck current, pi, ZT, tau and P are Peltier coefficients, thermoelectric figure of merit factors, nonlinear beam characteristic relaxation time and thermal power density of electron kinetic energy conversion of thermoelectric materials, and the nonlinear 2 omega Seebeck current I_2ωThe size of (a) reflects the non-uniformity of the distribution of the micro-area thermoelectric figure of merit factor behavior of the material sample under test.

2. The scanning thermoelectric microscopy apparatus for thermoelectric figure of merit behavior microscopy imaging as defined in claim 1, wherein said sub-surface thermoelectric signal in situ excitation module further comprises:

the device comprises an electron gun, an electron beam deflector, a signal generator, a scanning electron microscope lens barrel, a scanning electron microscope sample chamber and a thermoelectric signal detector, wherein the signal generator controls the electron beam deflector, an electron beam emitted from the electron gun passes through the electron beam deflector, enters the scanning electron microscope lens barrel and then enters the tested thermoelectric material sample on the scanning electron microscope sample chamber, and the thermoelectric signal detector is used for in-situ detection of a weak sub-surface thermoelectric current signal generated by the interaction of the tested thermoelectric material sample and a periodically modulated electron beam.

3. A scanning thermoelectric microscopy apparatus for thermoelectric figure of merit behavior microscopy according to claim 2,

the scanning electron microscope lens barrel comprises a first condenser lens, a second condenser lens, a scanning coil and an objective lens.

4. A scanning thermoelectric microscopy apparatus for thermoelectric figure of merit behavior microscopy according to any one of claims 1 to 3 wherein said thermoelectric signal detector further comprises:

the detector comprises a detector upper cover, a metal gasket, an insulator, a detector shell, a signal output end and a positioning end, wherein the detector upper cover is arranged on a tested thermoelectric material sample, the bottom of the tested thermoelectric material sample is sequentially provided with the metal gasket, the insulator, the detector shell and the positioning end which are sequentially connected, and the signal output end is connected with the bottom of the metal gasket and used for effectively outputting the thermoelectric signal.

5. A scanning thermoelectric microscopy apparatus for thermoelectric figure of merit behavior microscopy according to claim 4,

the sub-surface thermoelectric signal in-situ detection module further comprises: the signal end of the thermoelectric signal detector, the preamplifier and the phase-locked amplifier are connected in sequence to realize the seebeck current I of the nonlinear 2 omega_2ωIn situ detection and processing.

6. A scanning thermoelectric microscopy apparatus for thermoelectric figure of merit behavior microscopy according to claim 5,

the sub-surface thermoelectric signal microscopic imaging module further comprises: a scanning electron microscope control system and a computer system, which is used for realizing the in-situ real-time processing of the sub-surface thermoelectric signal and displaying the high-resolution microscopic imaging result.

7. A scanning thermoelectric microscopy apparatus for thermoelectric figure of merit behavior microscopy according to claim 6,

the electron beam deflector is arranged between a first-stage diaphragm and a second-stage diaphragm in the scanning electron microscope lens barrel.

8. A scanning thermoelectric microscopy apparatus for thermoelectric figure of merit behavior microscopy according to claim 7,

the electron beam deflector is composed of a pair of parallel metal polar plates, one end of the electron beam deflector is grounded, the other end of the electron beam deflector is connected with the output end of the signal generator, and the distance between the parallel metal polar plates is 3-10 mm.

9. A scanning thermoelectric microscopy apparatus for thermoelectric figure of merit behavior microscopy according to claim 8,

the range of the alternating excitation voltage amplitude at two ends of the electron beam deflector is 30V-100V, and the range of the working frequency is 1 kHz-200 kHz, so that the periodic modulation of the electron beam is realized.