Stereo temperature wave measurement device and method

Abstract

To provide a stereo temperature wave measurement device and method capable of easily measuring a heat flow direction in an anisotropic material or in a composite material, the method beng a novel hot transport evaluation system in a STEM.SOLUTION: The invention comprises: a heating unit for heating, using a pulse-state electron beam with a prescribed frequency (f), first and second contact pieces which are formed of a second metal material for generating thermal electromotive force to a first metal material, and which contact at two positions (T1 position (F point), T2 point (E point)) of a sample formed of a first metal material, and at least one heating point on the sample; and a device for detecting outputs of the first and second contact pieces being response to temperature rise of contact points between the first and second contact pieces due to heating of the pulse-state electron beam with a prescribed frequency, and measuring an amplitude component of a temperature wave corresponding to the heating position of the heating point by the prescribed frequency. By determining a rate of the heat flow flowing into the contact points (T1 point (F point), T2 point (E point)), the heat flow direction of the sample can be determined.SELECTED DRAWING: Figure 6B

Description

[Technical Field]

[0001] The present invention relates to a device for measuring temperature, relative heat flow direction, and thermal resistance on the nano- and micro-scale, and more specifically to a stereo temperature wave measurement device and method suitable for use in nano-scale heat transport evaluation in a transmission electron microscope using an electron beam pulse and a micro-thermocouple. [Background technology]

[0002] In recent years, there has been a demand for the development of new nanoscale heat transport evaluation methods aimed at controlling the thermal properties of thermoelectric materials and developing materials and devices for precise thermal control. The present inventors have been developing a scanning transmission electron microscope (STEM)-based thermal analytical microscopy (STAM) method that combines nanothermocouples fabricated by electrolytic polishing with a local heating technique using electron beam irradiation (see Patent Document 1 and Non-Patent Document 1). Here, electrolytic polishing refers to a method in which a product is placed on the positive side and a direct current is passed through an electrolyte to dissolve the metal surface, thereby achieving a polishing effect. The STAM method utilizes the temperature rise caused by plasmon excitation during electron beam irradiation, and has the advantage of being able to evaluate the heat passing through the sample based on Fourier's law by two-dimensionally recording the steady-state temperature (thermoelectric power) corresponding to each heating position during STEM scanning. Furthermore, the inventors have developed a pulsed STAM method based on the STAM method, proposing a new method for evaluating heat transport in STEM based on temperature wave phase measurement, which is relatively insensitive to changes in heat absorption due to differences in sample thickness and type of material (see Non-Patent Document 4). The pulsed STAM method uses temperature wave thermal analysis.

[0003] Temperature wave thermal analysis is used to measure the thermal diffusivity of small amounts of thin materials, primarily thin polymeric materials (see Patent Document 2 and Non-Patent Documents 2 and 3). In temperature wave thermal analysis, a weak temperature wave with an amplitude of 1°C or less is applied to a sample, its propagation is analyzed, and the thermal conductivity (λ) is determined from the temperature amplitude attenuation, and the thermal diffusivity (α) is determined from the phase delay measurement. Known methods for applying thermal stimuli include pulse (flash method), step (hot wire method), alternating current (temperature wave method), and differential scanning calorimetry (DSC). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6164735 Claim 17 [Patent Document 2] Patent No. 5489789 [Non-patent literature]

[0005] [Non-Patent Document 1] N. Kawamoto et al., Nano Energy, 52 323-328 (2018). [Non-patent document 2] Junko Morikawa and Toshimasa Hashimoto, "Measurement of Thermal Diffusivity and Thermal Conductivity Using Temperature Waves," Network Polymers, Vol. 34, No. 2 (2013) [Non-patent document 3] Toshimasa Hashimoto and Junko Morikawa, "Fourier Transform Temperature Wave Thermal Analysis," Thermal Measurements Vol. 27 No. 3, 141-151 (2000) [Non-patent document 4] NIMS, JST, January 16, 2024, Direct observation of heat transfer at the nanoscale ~Development of a new electron microscope method capable of quantitatively measuring thermal diffusion~, https: / / www.jst.go.jp / pr / announce / 20240116-2 / pdf / 20240116-2.pdf Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional monaural temperature wave measuring devices as micro-thermal conductivity measuring devices, such as those shown in Patent Document 1 and Non-Patent Document 1, the temperature at each heated point in a steady state after the temperature has risen to its maximum is recorded two-dimensionally at the nano-thermocouple contact point (fixed). When analyzing thermal conductivity based on Fourier's law using a conventional monaural temperature wave measuring device, it is necessary to prepare a sample in which a reference material with known thermal conductivity and a measurement sample are arranged in series, and the sample must be rod-shaped and have as uniform a thickness as possible, which poses the problem of time-consuming sample preparation. In other words, with the STAM method, the amount of heat input by electron beam irradiation depends on differences in sample thickness and the plasmon mean free path of the irradiated material, so heat transport evaluation poses challenges such as the need to prepare samples with as uniform a thickness as possible and to take into consideration the amount of heat input during analysis. Furthermore, the pulsed STAM method measures heat flow one-dimensionally, with one electron beam irradiation position and one temperature measurement point. However, in anisotropic materials and composite materials, the heat flux changes depending on the direction of the heat flow, so one-dimensional heat flow measurements either cannot measure three-dimensional heat flow, or one-dimensional heat flow measurements must be performed sequentially at observation points arranged two-dimensionally, which poses the problem of enormous measurement time and data analysis burden.

[0007] The present invention aims to solve the above-mentioned problems and to provide a stereo temperature wave measurement device and method, which is a new method for evaluating heat transport in a STEM, that can easily measure the heat flow direction in anisotropic materials and composite materials. [Means for solving the problem]

[0008] [1] According to the stereo temperature wave measuring device of the present invention, as shown in, for example, Fig. 6B, Fig. 7 and Fig. 9A, a first contactor 28 and a second contactor 29 made of a second metal material contact a sample 25 made of a first metal material or a conductive composite material containing the first metal material at two points (point T1 (point F) and point T2 (point E)) and generate a thermoelectric power to the first metal material; A heating device 10 for heating at least one heating point on a sample 25 using a pulsed electron beam 22 having a predetermined frequency (f); a device (42, 44, 50) for detecting outputs of the first contactor (28) and the second contactor (29) in response to a temperature rise at the contact point between the first contactor (28) and the second contactor (29) due to heating by the pulsed electron beam (22) of the predetermined frequency (f), and measuring an amplitude component of a temperature wave corresponding to the heating position of the heating point by the predetermined frequency (f); When generating thermoelectromotive force at the first contactor 28 and the second contactor 29, a portion (25b, 26, 27) that holds the sample 25 within an area irradiated with the pulsed electron beam 22 is used as a reference junction, and the contact points between the first contactor 28 and the second contactor 29 and the sample 25 are used as first and second temperature measuring junctions, and thermoelectromotive force is generated. The amplitude component of the temperature wave generated by the pulsed electron beam 22 (T E (x), T F (y)), the amplitude ratio (T E (x) / (T E (x)+T F (y)), the direction of heat flow in the sample 25 is determined by calculating the proportion of heat flowing into the contact points (point T1 (point F), point T2 (point E)).

[0009] [2] In the stereo temperature wave measuring device [1] of the present invention, preferably, the amplitude ratio (T E (x) / (T E (x)+T F (y)) may be calculated by the following formula:

number

[10] In the stereo temperature wave measuring device [1] of the present invention, it is preferable that the thickness of the sample 25 at the first contactor 28, the second contactor 29 and the heated point by the electron beam 22 is thinner than the thickness of the portions (25b, 26, 27) that hold the sample 25 within the area irradiated by the electron beam 22.

[11] In the stereo temperature wave measuring device [1] of the present invention, it is preferable that the measurement timing of the device for measuring the phase component of the temperature wave is a state in which the temperature oscillates with a small amplitude at a temperature that has been raised to a substantially steady state by the pulsed electron beam. Here, the small amplitude means an amplitude that is small compared to the amount of change in the temperature that has been raised to a steady state by the pulsed electron beam, for example, an amplitude that is 1 / 10 or less of the amount of change in the temperature.

[12] In the stereo temperature wave measuring device [1] to

[11] of the present invention, it is preferable to further include an analysis computer, and the analysis computer calculates the amplitude component (T E (x), T F (y)), the amplitude ratio (T E (x) / (T E(x)+T F The direction of heat flow in the sample 25 may be determined by calculating the proportion of heat flowing into the contact points (points F and E) based on (y).

[0010]

[13] According to the stereo temperature wave measuring method of the present invention, as shown in FIG. 8, for example, first and second contactors (28, 29) made of a second metallic material that generates a thermoelectric power to the first metallic material are brought into contact with a sample 25 made of a first metallic material or a conductive composite material containing the first metallic material at two locations (point T1 (point F), point T2 (point E)) (S804), and the heating points on the sample 25 are heated using a pulsed electron beam 22 of a predetermined frequency (f) (S806). The outputs of the first and second contactors responding to the temperature rise at the contact points (point T1 (point F), point T2 (point E)) with the first and second contactors (28, 29) due to heating by the pulsed electron beam 22 of the predetermined frequency are detected (S808), and the amplitude component of the temperature wave corresponding to the heating position of the heating point by the predetermined frequency is measured (S810). E (x), T F (y)) to measure the amplitude ratio (T E (x) / (T E (x)+T F Based on the result of (y), the ratio of the heat flow flowing into the contact points (points F and E) is calculated (S812), and the direction of the heat flow in the sample 25 is calculated (S814).

[0011]

[14] In the stereo temperature wave measurement method

[13] of the present invention, preferably, the amplitude ratio (T E (x) / (T E (x)+T F (y)) may be calculated by the following formula:

number

[15] In the stereo temperature wave measurement method

[13] of the present invention, preferably, a plurality of outputs of the first and second contacts (28, 29) in response to the temperature rise of the contact points (point T1 (point F), point T2 (point E)) caused by heating with the pulsed electron beam 22 of a predetermined frequency are detected, and the phase components of the temperature waves corresponding to the heating positions of the heating points caused by the electron beam 22 of the predetermined frequency are measured; The phase component (θ) of the temperature wave generated by the pulsed electron beam is used to calculate the distance (L) from the heating point to the contact points (T1 point (F point), T2 point (E point)) of the first and second contacts on the sample 25. F , L E ) the thermal diffusivity (α) between the heating point and the contact point can be calculated using the following formula: α=πf / (θ / L F ) 2 or α=πf / (θ / L E ) 2

[16] In the stereo thermal wave measurement method

[13] of the present invention, preferably, the sample 25 is placed in a TEM or STEM so that its TEM image or STEM image can be observed; The electron beam 22 may be irradiated by an electron gun of a TEM or STEM.

[17] In the stereo thermal wave measurement method

[13] of the present invention, preferably, in a state where the contact between the sample 25 and the first and second contactors (28, 29) is released, a plurality of calibration outputs corresponding to the heating positions of the plurality of heating points from the first and second contactors (28, 29) are detected; The influence of secondary electrons generated by irradiation of the electron beam onto the plurality of heating points on the outputs of the first and second contacts (28, 29) can be canceled out by the plurality of calibration outputs.

[18] In the stereo thermal wave measurement method

[13] of the present invention, preferably, the heating points on the sample 25 are a plurality of heating points having different distances (L) to the contact points of the first and second contactors (28, 29) on the sample.

[19] In the stereo temperature wave measurement method

[13] of the present invention, the predetermined frequencies are preferably a plurality of frequencies selected between 1 Hz and 1 MHz.

[20] In the stereo temperature wave measurement method

[13] of the present invention, preferably, the pulsed electron beam of a predetermined frequency (f) has an on-off duty ratio selected between 1:9 and 9:1, and the pulse on-time width selected between 100 ns and 1 sec.

[21] In the stereo temperature wave measurement method

[13] of the present invention, the timing for measuring the phase component of the temperature wave is preferably when the temperature is oscillating with a small amplitude at a temperature that has been raised to a substantially steady state by the pulsed electron beam. Here, the small amplitude refers to an amplitude that is small compared to the amount of change in the temperature that has been raised to a steady state by the pulsed electron beam, for example, an amplitude that is 1 / 10 or less of the amount of change in the temperature. [Effects of the Invention]

[0012] According to the stereo temperature wave measurement device and method of the present invention, the heat flow direction of a sample is measured using the stereo temperature wave amplitude ratio method, so that even if the sample is made of a first metal material or a conductive composite material containing the first metal material, the heat flow direction can be easily measured in anisotropic materials and composite materials. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the overall configuration of a monaural temperature wave phase measurement device. [Figure 2A] Photo of a TEM holder with a nanothermocouple attached. [Figure 2B] TEM image showing nanothermocouple in contact with sample [Figure 2C] FIG. 1 is a diagram illustrating the propagation of a temperature wave when a heating point on a sample is heated by an electron beam. [Figure 3A] This is an explanatory diagram of the principle of the monaural temperature wave phase measurement method, showing the frequency method. [Figure 3B] This is an explanatory diagram of the principle of the monaural temperature wave phase measurement method, showing the distance method of the heating position. [Figure 4] 1 is a flowchart illustrating a monaural temperature wave phase measurement method. [Figure 5] A conceptual diagram modeling an example configuration that can determine the absolute value of thermal conductivity. [Figure 6A] 1 is a diagram showing a main configuration of an example of a detection unit of a stereo thermal wave measuring device according to the present invention. FIG. [Figure 6B] 1 is a signal processing circuit diagram of a main part of a stereo temperature wave measuring device according to the present invention; [Figure 7] 1 is a diagram showing the overall signal processing circuit of a stereo temperature wave measuring device according to the present invention; [Figure 8] 1 is a flowchart illustrating a stereo temperature wave amplitude measurement method. [Figure 9A] 1 is an explanatory view of an overall view of a dissimilar material joint for stereo thermal wave measurement used in the present invention. [Figure 9B] This is an explanatory diagram showing an enlarged view of the main part of the dissimilar material joint for stereo thermal wave measurement used in the present invention, where (b) shows the contact point (point F) between the first contactor 28 and the sample 25, and (c) shows the contact point (point E) between the second contactor 29 and the sample 25. [Figure 10A] FIG. 1 shows a junction of dissimilar materials observed by HAADF-STEM. [Figure 10B] FIG. 1 shows the results (amplitude image and phase image) of stereo thermal wave measurement. [Figure 11A] This figure shows the amplitude images measured at two points for amplitude ratio analysis, and shows the amplitude images measured at the contact point (point E) and the contact point (point F) separately. [Figure 11B] FIG. 10 is a diagram showing an analysis of the amplitude ratio of a temperature wave using an analysis of an amplitude image. [Figure 12] FIG. 1 is an explanatory diagram of a local heat flow analysis using stereo thermal wave measurement. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following definitions are given for the academic terms used in this specification. Fourier's law describes the relationship between the amount of heat transferred in conductive heat transfer and is expressed by the following equation:

number

[0015] Thermal conductivity is a coefficient that determines the speed at which thermal energy is transferred due to a temperature gradient. Specifically, when the amount of heat flowing per unit cross-sectional area per unit time, i.e., heat flux, is proportional to the temperature gradient, the relationship between heat flux (J) and temperature (T) gradient is expressed as the following equation (2), where λ is the coefficient. J=-λgradT (2) If we express the relationship between temperature and heat in a material more generally using Gauss's divergence theorem, we can derive the following heat conduction equation: ∂q / ∂t=∇ 2 λT (3) Here, q is the amount of heat per unit volume, and it is assumed that there is no heat absorption or heat generation within the material. If the thermal conductivity (λ) is constant regardless of position or time, then equation (3) becomes ∂q / ∂t=λ∇ 2 T (4) This becomes:

[0016] Thermal diffusivity is a coefficient that determines the speed at which temperature propagates through a temperature gradient. Specifically, it is the proportionality coefficient α in the thermal diffusion equation (equation (5)) derived by converting the amount of heat (q) into temperature (T) in equation (4). ∂T / ∂t=α∇ 2 T (5) The relationship between thermal conductivity (λ) and thermal diffusivity (α) is: λ=α·Cp·ρ (6) These are related as follows, and together with ρ (density) and Cp (specific heat capacity at constant pressure), they are called the four thermal constants. When measuring, either thermal conductivity or thermal diffusivity is calculated and converted using equation (6). As with material diffusion, the longer the diffusion distance and the smaller the thermal diffusivity, the longer it takes to homogenize.

[0017] Temperature wave is a method of measuring amplitude attenuation and phase delay by applying a weak AC stimulus of thermal energy to a sample. To popularize the measurement method, it was standardized as ISO22007-3 (for thin films using phase analysis) in the field of thermal conductivity of plastics (TC-61) in 2008, and furthermore, amplitude analysis type was also certified as ISO-22007-6. In the case of an AC temperature wave, the thermal diffusion length (μ) is defined as follows as a measure of the distance required for the temperature to be uniform: μ=√2α / ω (7)

[0018] Next, in explaining the principle of the present invention, monaural temperature wave measurement, which is a prerequisite for stereo temperature wave measurement, will be explained. The monaural temperature wave measuring device and method that are the premise of the present invention measure thermal diffusivity (α) using a temperature wave phase method, and are based on the following one-dimensional heat conduction equation:

number

number

[0019] In detecting the amplitude and phase of the temperature wave, the phase change (Δθ) occurring between heating positions is given by the following equation:

number

[0020] Next, a description will be given of the calculation formula specific to the stereo temperature wave measuring device and method of the present invention. The two contact points where the first and second thermocouples come into contact with the sample are designated as points F and E. Then, the amplitude component of the temperature wave detected at point E is given by the following equation, based on the above equation (9):

number

number

number

[0021] [Monaural temperature wave measuring device (micro thermal conductivity measuring device)] FIG. 1 is a diagram showing the overall configuration of a monaural temperature wave measurement device, which is the premise of stereo temperature wave measurement. In the figure, the monaural temperature wave measuring device comprises a transmission electron microscope 10, a temperature wave generating unit 20, a lock-in amplifier 30, a signal processing unit 40, an electron beam control and image processing system 50, and an analysis computer 60. The transmission electron microscope 10 includes an electrostatic shutter 12, a shutter driver 13, an electrostatic dose modulator (EDM) 14, a synchronization signal generator 15, an attenuation adjustment knob 16, and a control software unit 18. The temperature wave generating unit 20 is an enlarged view of the electron beam irradiation area of ​​the transmission electron microscope 10 shown in Figure 1. The temperature wave generating unit 20 is equipped with a sample 21, a pulsed electron beam 22, a constantan probe 23, and a chromel probe 24. Details will be explained using Figures 2A and 2B. Examples of the sample 21 include, but are not limited to, single crystal sapphire, α-Al2O3 (alumina), polycrystalline aluminum nitride (AlN), insulating ceramic materials, and various thermoelectric materials. Examples of the sample 21 include insulators, semiconductors, metals, nanowires, nanotubes, particles, thermally conductive fillers, composite heat dissipation materials, etc. The physical properties to be measured include, for example, heat transport measurements and specific heat measurements of the sample 21. In the lock-in amplifier 30, a constantan probe 23 and a chromel probe 24 of the thermocouple are connected to the input terminal, and a synchronization signal generator 15 is connected to the reference terminal.

[0022] The signal processing unit 40 includes an amplifier circuit, a filter circuit, and an attenuation circuit. The electron beam control and image processing system 50 can be, for example, a DigiScan™ system provided by Gatan, Inc., a member company of the Electronic Instruments Business Group of AMETEK Corporation. Electron beam control signals and image signals processed by a signal processing unit 40 are sent to the input terminal, and an analysis computer 60 is connected to the output terminal. The electron beam control and image processing system 50 can measure the phase component of a temperature wave corresponding to the heating position of a heating point heated by a specified frequency using the STEM image obtained by the transmission electron microscope 10. The analytical computer 60 inputs the amplitude and phase of the temperature wave measured by the electron beam control and image processing system 50 and calculates the thermal conductivity of the sample 21. For this calculation, for example, a Gatan digital micrograph (trademark) may be used, in which a script for dividing the position information is actually written and converted into a thermal diffusivity image. Alternatively, instead of using the analytical computer 60, a line profile of the phase image of the rod-shaped sample may be taken and the thermal diffusivity (α) may be calculated in Excel (trademark) using the following equation: α=πf / (θ / L) 2 (14) The signal processing unit 40, the electron beam control and image processing system 50, and the analysis computer 60 are well known to those skilled in the art, or can be constructed by those skilled in the art without exerting any special inventive effort based on the descriptions in this specification and the drawings, so specific explanations and illustrations will be omitted.

[0023] The electrostatic dose modulator (EDM) 14 is a high-speed beam blanking system with pre-sample electrostatic deflectors, including electronics and software control. With the EDM, the beam can be switched on or off in less than 50 ns. This blanking speed is approximately 10,000 to 100,000 times faster than the opening and closing speed of conventional electrostatic shutters 12, instantly improving the clarity of data acquired with fast exposure times. The EDM can also attenuate electron irradiation without affecting imaging conditions, giving TEM and STEM users exceptional control over the dose delivered to the sample. With state-of-the-art electronics and software add-ons, the EDM enables advanced applications such as time-dose structuring and STEM synchronization.

[0024] The electron beam control and image processing system 50 can be connected to a STEM device, and a common user interface allows for flexible setting of scan conditions and digitization gradation to acquire images suited to the experiment. For example, the DigiScan™ system allows for up to four synchronized input channels as standard, and is equipped with analog or pulse input and the ability to set the number of pixels in the X and Y directions up to 32k x 32k pixels, but is not limited to this number of channels or pixels. The pixel dwell time can be set within the range of 50 ns to 400 ms per pixel. "Dwell time" refers to the time the electron beam remains at one pixel when acquiring a STEM image by electron beam scanning. Dwell time is an indicator of the electron beam scanning speed. Multiplying the retention time by the number of scan pixels in one horizontal line scan and adding the flyback time gives the scan time for one horizontal line scan. Multiplying this scan time by the number of vertical scans (horizontal scan lines) calculates the acquisition time for one scanned image.

[0025] Figure 2A is a photograph of a TEM holder with a nano-thermocouple attached, and Figure 2B is a TEM image showing the state where the nano-thermocouple is in contact with the sample. As shown in paragraph numbers 0013 to 0019 of Patent Document 1, Cu 55 Ni 45 (mass %) (Constantan (trademark)) probe and Cr 10 Ni 90 (mass %) (Chromel (trademark)) probe were combined to fabricate a Constantan - Chromel nano-thermocouple. As a result, the operating temperature range could be significantly expanded to -200°C < T < 800°C. Also, low thermal conductivity, large thermoelectric power, linear responsiveness, high resolution of the measured temperature reaching 10 -2 K, high responsiveness with a tiny junction realized, and the ability to introduce the thermocouple material into a strong magnetic field space such as inside a transmission electron microscope because the thermocouple material is a combination of non-magnetic materials, etc., enabled performance improvement in various aspects. Also, in this manufacturing method, nano-thermocouples can be fabricated using other thermocouple materials according to the application.

[0026] [Method for manufacturing a nano-thermometer] By means of electrolytic polishing, microprobes with the tip diameters of Cu-Ni and Cr-Ni wires sharpened to 100 nm or less were fabricated respectively. Specifically, by precisely controlling the positions of these microprobes using a piezo element inside a transmission electron microscope (TEM) and bringing the tip parts of these microprobes into contact with each other, and passing a current of about 10 μA between the probes, a junction with an extremely small contact resistance between the Constantan wire and the Chromel wire shown in Figure 2B was formed, and a nano-thermocouple, that is, a nano-thermometer, was fabricated. In the mono temperature wave measuring device configured in this manner, by irradiating the sample 21 with a focused electron beam, heat is applied to a nanoscale region on the sample 21, and the location and amount of heat input can be controlled.

[0027] Figure 2A shows a photograph of the holder used to attach the nanothermocouple fabricated in this way and measure the temperature of a microscopic region on a target sample within a TEM. Figure 2A also shows a schematic of a voltmeter used to measure the thermoelectric power generated in the nanothermocouple within the holder. It is important to note that because a large magnetic field (e.g., 2 T in this example) is applied to the sample position within the TEM, the holder material, and in particular the nanothermocouple, must be made of a nonmagnetic material. In this example, this condition is satisfied by using chromel and constantan as the nanothermocouple materials. Note that in this example, α-Al2O3 (hereinafter simply referred to as alumina), which can be used as a filler in composite materials, is used as the sample, but it is of course possible to use various other materials as the sample to be measured.

[0028] [Heat application and temperature measurement at the nanoscale] The holder with the nanothermocouple attached as described above is placed inside the TEM, and the tip (junction) of the nanothermocouple is brought into contact with the sample as shown in FIG. 2B. Here, an electron beam is irradiated near the tip of the thermocouple, and the thermoelectromotive force generated in the nanothermocouple changes depending on whether the electron beam is turned on or off. The electron gun used to irradiate the electron beam can be the same as that used in TEMs. Furthermore, the position where the nanothermocouple contacts the sample and the irradiation position of the focused electron beam can be accurately determined by observation using a TEM. In this way, the irradiation position can be determined by referring to the TEM image, allowing for a greater degree of measurement flexibility than methods that require the position to be heated to be determined in advance and then a specialized sample prepared for that purpose.

[0029] Importantly, the location where heat is applied by the electron beam and the location where the temperature is measured do not need to be spatially coincident, and the electron beam can be irradiated at any point on the sample other than the contact point of the nanothermocouple, allowing for analysis of the heat conduction in a desired section on the sample.

[0030] FIG. 2C is a diagram illustrating the propagation of a temperature wave when a heating point on a sample is heated by an electron beam. In a one-dimensional sample 21, the position where a thermocouple, a constantan probe 23 and a chromel probe 24, are connected to one end of the sample 21 is set as the origin, and the coordinates of the irradiation position of the pulsed electron beam 22 are set as x0, x1, and x2. i , t) (i=0, 1, 2), the amplitude attenuates with distance, but the following equation holds for the phase lag (θ): θ1=k(x1-x0) (15) θ2=k(x2-x0) (16)

[0031] Figure 3A is an explanatory diagram of the principle of the temperature wave method, showing the frequency method (frequency control). (A) shows the heating position of the sample using a pulsed electron beam and the thermocouple attachment position, and (B) shows the phase delay (θ). The horizontal axis shows the square root of frequency (√f) and the vertical axis shows the phase. In Figure 3A, T M indicates the position where the thermocouple is attached to the sample, and the distance (L) indicates the distance between the position where the sample is heated by the pulsed electron beam and the position where the thermocouple is attached. The phase lag (θ) increases at the rate of the square root of the frequency (√f) as the frequency (f) increases.

[0032] Figure 3B is an explanatory diagram of the principle of the temperature wave method, showing the heating position distance method (Heating position control). (A) shows the heating position of the sample using a pulsed electron beam and the thermocouple attachment position, and (B) shows the phase delay (θ). The horizontal axis shows the square root of frequency (√f), and the vertical axis shows the distance (L) between the heating position of the sample using a pulsed electron beam and the thermocouple attachment position. In Figure 3B(A), the heating position of the sample by the pulsed electron beam is moved from a position close to the thermocouple attachment position to the other end of the sample. The phase lag (θ) increases in proportion to the increase in the distance (L) between the heating position of the sample by the pulsed electron beam and the thermocouple attachment position.

[0033] FIG. 4 is a flowchart illustrating the monaural temperature wave measurement method of the present invention. First, the sample 21 is placed in a TEM or STEM so that its TEM or STEM image can be observed (S402). Next, thermocouples (23, 24) are brought into contact with the sample 21 (S404). Next, at least one heating point on the sample 21 is heated using a pulsed electron beam of a predetermined frequency (f) (S406). The signal processing unit 40 detects multiple outputs of the thermocouples (23, 24) in response to the temperature rise at the contact point due to heating by the pulsed electron beam of a predetermined frequency (S408). If necessary, the positional and temporal relationship between the multiple output signals of the thermocouples (23, 24) by the signal processing unit 40 and the electron beam irradiated by the transmission electron microscope 10 is linked by the electron beam control and image processing system 50. The electron beam control and image processing system 50 measures the phase components of the temperature waves corresponding to the heating positions of the heating points at a predetermined frequency (S410). The analytical computer 60 uses the phase component (θ) of the temperature wave generated by the pulsed electron beam to determine the thermal diffusivity (α) between the heated point and the contact point based on the distance (L) from the heated point to the contact point of the thermocouples (23, 24) on the sample 21 using the following equation (S412). α=πf / (θ / L) 2 (14)

[0034] Preferably, the reliability of the monaural temperature wave measurement method of the present invention can be improved by performing a calibration operation at regular intervals or when deemed necessary. In the calibration operation, a plurality of calibration outputs corresponding to the heating positions of a plurality of heating points from the thermocouples (23, 24) are detected while the sample 21 is released from contact with the thermocouples (23, 24), and the influence of secondary electrons caused by the irradiation of the electron beam 22 onto the plurality of heating points on the outputs of the thermocouples (23, 24) is canceled out by the plurality of calibration outputs.

[0035] A specific example of the device configured in this way will be described. In Figure 5, (A) is a conceptual diagram modeling an example of a configuration that can determine the absolute value of thermal conductivity of a conventional device, and (B) is a line graph showing the relationship between the distance from the tip of the thermocouple to the electron beam irradiation position and the temperature rise at the tip of the thermocouple due to the irradiation. In Figure 5(A), the sample 21 has a measured sample portion 212, a standard material portion 214, electron beam heat conversion portions 216a, 216b, and 216c, a thermal resistance portion 218, and a base portion 219. The measured sample portion 212 is a portion where the thermal conductivity (k) of the sample is measured. The standard material portion 214 is a standard material with a known thermal conductivity (k). The electron beam heat conversion portions 216a, 216b, and 216c are "the same sample" made of a heavy element (e.g., tungsten W) that has a high heat conversion rate and a relatively large heat input when irradiated with an electron beam. They are divided into three portions so as to sandwich the standard sample portion 214 and the measured sample portion 212. The irradiation portions of the pulsed electron beam 22 are the electron beam heat conversion portions 216a, 216b, and 216c so that all electron beam irradiation points are made of the same material so that the amount of heat absorbed during electron beam irradiation is the same at all irradiation points. The thermal resistance portion 218 is made of, for example, epoxy resin, and has a sufficiently large thermal resistance at the end opposite to the end that contacts the thermocouples 23 and 24. The pedestal portion 219 supports the entire sample 21, and supports the electron beam heat conversion portions 216a, 216b, 216c, etc. and the thermocouples 23 and 24 via the thermal resistance portion 218.

[0036] In a system configured as described above, an electron beam is irradiated onto points on the electron beam heat conversion units 216a, 216b, and 216c on a sample placed in a TEM, whereby heat is applied to the points, causing a temperature rise. This creates a temperature gradient, which generates a heat flow. In Figure 5(A), heat flow can occur to both the left and right sides of the electron beam irradiation point. However, heat flow to the right is largely blocked by the low thermal conductivity (i.e., high thermal resistance) of the thermal resistance unit 218 (epoxy resin) used to bond the sample 21 to the pedestal 219. Therefore, most of the heat flow flows to the left side of Figure 5, eventually reaching the thermocouples 23 and 24 at the left end, causing a temperature change at this location. By providing electron beam heat conversion units 216a, 216b, and 216c, it is also possible to measure the thermal conductivity of samples made of light elements that are difficult to convert into heat when irradiated with an electron beam, in which the sample to be measured 212 is irradiated with an electron beam. Even if the sample to be measured 212 is made of light elements such as carbon nanotubes, graphene, or epoxy resin, which are more transparent to electron beams, the sample is not directly irradiated with an electron beam, and therefore the problem of insufficient heat input due to poor heat absorption, which occurs when irradiated with an electron beam directly, can be overcome.

[0037] In the configuration shown in Figure 5(A), of the electron beam irradiation points (1) to (6), points (2) and (3) are located near the measurement sample on the upstream and downstream sides of the measurement sample portion 212 in relation to the direction of heat flow. Points (4) and (5) are also located near the upstream and downstream sides of the reference material portion 214 in relation to the direction of heat flow. By irradiating this configuration with an electron beam as described above and measuring the temperature change at the left end with a thermocouple, the graph shown in Figure 5(B) is obtained. Because the electron beam is irradiated entirely onto the tungsten portion, the amount of heat absorbed by the sample upon each irradiation is the same. The heat flow path lengths in the measurement sample and the reference material can be measured by TEM observation, etc. Therefore, the slope of the line between points (2) and (3), ΔT sample / Δx sample, and the slope of the line between points (4) and (5), ΔT reference material / Δx reference material, can be calculated.

[0038] Now, using the known thermal conductivity (k) of the standard material, the thermal conductivity (k) of the sample can be expressed as follows: k standard material = αk sample (17) where: α = (ΔT sample / Δx sample) / (ΔT standard material / Δx standard material) (18) Since the numerator and denominator of the fractional expression representing α can be calculated as described above, the absolute value of the thermal conductivity (k) of the sample can also be calculated.

[0039] In this way, by using a standard material with known thermal conductivity to estimate the heat energy generated during electron beam irradiation, it becomes possible to estimate the absolute value. That is, in order to ensure that the heat flow passes through a material with known thermal conductivity (standard material portion 214), the standard material portion 214 sandwiched between electron beam heat conversion portions 216a, 216b, and 216c is provided in the path of the heat flow.

[0040] Furthermore, if the thermal conductivities of the electron beam thermal conversion parts 216a, 216b, and 216c sandwiching the measurement sample part 212 in the above description under the intended use environment are known, the standard material part 214 can be made of the same material as the electron beam thermal conversion parts 216a, 216b, and 216c. If the standard material part 214 is made of the same material as the electron beam thermal conversion parts 216a, 216b, and 216c, the structure on the left side of (3) in Figure 5(A) is simplified to an integrated structure made only of the same material as the electron beam thermal conversion parts 216a, 216b, and 216c. The above-mentioned formula for calculating the absolute value of thermal conductivity can also be modified accordingly.

[0041] [Stereo thermal wave measurement device (heat flow direction measurement device for anisotropic materials and composite materials)] Fig. 6A is a diagram showing an example of the main configuration of a detection unit of a stereo temperature wave measuring device of the present invention. Fig. 6B is a diagram showing a main signal processing circuit of a stereo temperature wave measuring device of the present invention. Fig. 7 is a diagram showing the entire signal processing circuit of a stereo temperature wave measuring device of the present invention. The stereo thermal wave measurement device of this embodiment includes a heating device 10 (not shown), a tungsten reference temperature section 26, a sample stage 27, a first contactor 28, a second contactor 29, lock-in amplifiers 30A and 30B, a signal switch 42, an offset / gain control device 44, an electron beam control and image processing system 50, and an analysis computer 60. Furthermore, a sample 25 to be measured is mounted on a sample stage 27 via a tungsten reference temperature part 26. The sample 25 is a metallic material or a conductive composite material containing a metal. The metallic material may be a material composed of multiple phases with different compositions or constituent elements, for example, a metallic material composed of multiple phases of different compositions with crystal grain sizes of sub-micrometers to several micrometers. An example of a conductive composite material containing a metal is a composite material composed of a conductive filler and an insulating resin. An example of the conductive filler is a conductive Ag paste, which is composed of Ag particles as a conductive filler in an insulating resin.

[0042] The sample 25 has a thin portion 25a, which serves as a heating point for the electron beam 22, and a thick portion 25b, which functions as a reference electrode and has negligible temperature fluctuations compared to the thin portion 25a. The sample 25 has a reduced heat capacity by making the thicknesses of the first contact 28, the second contact 29, and the thin portion 25a thinner than the thicknesses of the portions (thick portion 25b, tungsten reference temperature portion 26, and sample stage 27) that hold the sample 25 within the region irradiated by the electron beam 22. The thin portion 25a has a thickness sufficient to generate a temperature wave due to irradiation with the pulsed electron beam 22, preferably 200 nm, but not limited thereto, and preferably 100 to 300 nm. The thin portion 25a is preferably rectangular, with a length of 20 to 50 μm and a width of 5 to 15 μm. The thick portion 25b preferably has a heat capacity such that the temperature fluctuation as a reference electrode is negligible compared to the thin portion 25a even when it is exposed to a temperature wave caused by irradiation with the pulsed electron beam 22, and is preferably, for example, 1 to 2 μm, but is not limited to this, and is preferably, for example, 1 to 5 μm. The thick portion 25b is provided continuously with the thin portion 25a, and is preferably, for example, 2 to 5 μm in the length direction and 10 to 30 μm in the width direction. The tungsten reference temperature portion 26 is a jig used to mount the thick portion 25b on the sample stage 27, and is, for example, made into a comb-like tip of the sample stage 27. It is preferable that it has a thickness of, for example, 1 to 2 μm and has approximately the same shape as the thick portion 25b of the sample 25, but is not limited to this and may have a thickness of, for example, 1 to 5 μm. The sample stage 27 is a jig that holds the sample 25 within the electron beam irradiation area, and may be, for example, a molybdenum mesh from Omniprobe (manufactured by Oxford Instruments). The sample stage 27 has multiple comb-like tips, and by attaching multiple samples 25 to the comb-like tips, multiple samples 25 can be measured at the same time.

[0043] The first contactor 28 and the second contactor 29 are made of a second metallic material that generates a thermoelectric power with respect to the first metallic material, and contact a sample 25 made of the first metallic material or a conductive composite material containing the first metallic material at two different points (points T1 and T2 shown in FIGS. 6B and 7, which correspond to points F and E shown in FIGS. 9 and 10, respectively). The second metallic material is preferably chromel, constantan, or a metallic material that generates a large amount of thermoelectric power with respect to the first metallic material. The first contactor 28 and the second contactor 29 are preferably needle-shaped, and the diameter of the needle-shaped tip is preferably 100 nm or less.

[0044] The heating device 10 heats at least one heating point on the sample 25 using a pulsed electron beam 22 of a predetermined frequency (f). The heating device 10 uses an electron gun housed in a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM), but is not limited to this and may also be a device generating a beam of charged particles such as ions. The electron gun allows observation of a TEM image or STEM image, and irradiates the heated point on the sample 25 with a focused electron beam. The first lock-in amplifier 30A has an input terminal connected to the output terminal of the first contactor 28 and the tungsten reference temperature part 26, and a reference terminal connected to a synchronization signal generator (not shown) of the heating device 10. The second lock-in amplifier 30B has an input terminal connected to the output terminal of the second contactor 29 and the tungsten reference temperature part 26, and a reference terminal connected to a synchronization signal generator (not shown) of the heating device 10.

[0045] The signal switch 42 receives the amplitude and phase signals of the first lock-in amplifier 30A and the second lock-in amplifier 30B, and outputs the amplitude and phase signals of either the lock-in amplifiers 30A, 30B to the offset / gain control device 44. The signal switch 42 allows the offset / gain control device 44 and the electron beam control and image processing system 50 to simultaneously acquire the following seven image patterns: That is, a STEM image + a phase 1 image, a STEM image + a phase 2 image, a STEM image + an amplitude 1 image, a STEM image + an amplitude 2 image, a phase 1 image + a phase 2 image, an amplitude 1 image + a phase 1 image, an amplitude 1 image + an amplitude 2 image, or an amplitude 2 image + a phase 2 image. Here, the phase 1 and amplitude 1 images are sent from the lock-in amplifier 30A. The phase 2 and amplitude 2 images are sent from the lock-in amplifier 30B. The STEM images are sent from a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM) that constitutes the heating device 10. The offset / gain control device 44 controls the offset and gain of the amplitude signal and phase signal selected by the signal switcher 42 .

[0046] The electron beam control and image processing system 50 can be the DigiScan™ system described above. Electron beam control signals and image signals processed by the offset / gain control device 44 are sent to the input terminal, and an analysis computer 60 is connected to the output terminal. The electron beam control and image processing system 50 can measure the phase component of the temperature wave corresponding to the heating position of the heating point at a specified frequency using the STEM image obtained by the heating device 10. The analytical computer 60 inputs the amplitude and phase of the temperature wave measured by the electron beam control and image processing system 50 and calculates the direction of heat flow in the sample 25, which is an anisotropic material or a composite material. If the electron beam control and image processing system 50 has four-channel input terminals, there is no need to use the signal switch 42, and the amplitude and phase signals of the lock-in amplifiers 30A and 30B that have been signal-processed by the offset / gain control device 44 can be processed simultaneously.

[0047] Here, the lock-in amplifiers 30A, 30B, signal switch 42, offset / gain control device 44, and electron beam control and image processing system (DigiScan) 50 are devices that detect outputs from the first contactor 28 and the second contactor 29 in response to a temperature increase at the contact point between the first contactor 28 and the second contactor 29 due to heating by a pulsed electron beam 22 of a predetermined frequency, and measure the amplitude component of a temperature wave corresponding to the heated position of the heated point by the predetermined frequency (f). The lock-in amplifiers 30A, 30B, signal switch 42, offset / gain control device 44, and electron beam control and image processing system (DigiScan) 50 may also have a function of detecting outputs from the first contactor 28 and the second contactor 29 in response to a temperature increase at the contact point between the first contactor 28 and the second contactor 29 due to heating by a pulsed electron beam of a predetermined frequency, and measure the phase component of a temperature wave corresponding to the heated position of the heated point by the predetermined frequency.

[0048] The device configured in this manner operates as follows. When generating thermoelectric power in the first contactor 28 and the second contactor 29, the portion (thick portion 25b, tungsten reference temperature portion 26, sample stage 27) that holds the sample 25 within the area irradiated by the pulsed electron beam 22 is used as the reference junction, and the contact points between the first contactor 28 and the second contactor 29 and the sample 25 are used as the first and second temperature measuring junctions to generate thermoelectric power. The amplitude component of the temperature wave generated by the pulsed electron beam 22 (T E (x), T F(y)), the amplitude ratio (T E (x) / (T E (x)+T F (y)), the direction of heat flow in the sample 25 is determined by calculating the proportion of heat flowing into the contact points (point T1 (point F), point T2 (point E)).

[0049] This amplitude ratio (T E (x) / (T E (x)+T F (y)) is calculated by the following formula:

number

[0050] The predetermined frequency may be a plurality of frequencies selected from the range of 1 Hz to 1 MHz. The pulsed electron beam of the predetermined frequency (f) may have an on-off duty ratio selected from the range of 1:9 to 9:1, and the pulse on-time width selected from the range of 100 ns to 1 sec. The analytical computer 60 calculates the amplitude component (T E (x), T F (y)) to measure the amplitude ratio (T E (x) / (T E (x)+T F The direction of heat flow in the sample 25 can be determined by calculating the proportion of heat flowing into the contact points (points F and E) based on (y).

[0051] FIG. 8 is a flowchart illustrating the stereo temperature wave amplitude measurement method. In the stereo thermal wave measurement method of the present invention, a first contactor 28 and a second contactor 29 made of a second metallic material that generates a thermoelectric power to the first metallic material are brought into contact with a sample 25 made of a first metallic material or a conductive composite material containing the first metallic material at two points (point T1 (point F) and point T2 (point E)) (S804). Then, the heating points on the sample 25 are heated using a pulsed electron beam 22 of a predetermined frequency (f) (S806). Next, the lock-in amplifiers 30A and 30B detect the outputs of the first contactor 28 and the second contactor 29 in response to the temperature rise at the contact points with the first contactor 28 and the second contactor 29 due to heating by the pulsed electron beam 22 of a predetermined frequency (S808). The amplitude component of the temperature wave corresponding to the heating position of the heating point at a predetermined frequency is measured by the lock-in amplifiers 30A and 30B, the signal switch 42, the offset / gain control device 44, and the electron beam control and image processing system 50 (S810). Next, the analysis computer 60 calculates the amplitude component (TE (x), T F (y)), the amplitude ratio (T E (x) / (T E (x)+T F Based on the heat flow rate (y), the ratio of the heat flowing into the contact points (points F and E) is calculated (S812), and the heat flow direction of the sample 25 is calculated (S814).

[0052] Fig. 9A is an overall explanatory diagram of a dissimilar material joint for stereo thermal wave measurement used in the present invention. Fig. 9B is an explanatory diagram showing an enlarged view of the main part of the dissimilar material joint for stereo thermal wave measurement used in the present invention, where (b) shows the contact point (point F) between the first contactor 28 and the sample 25, and (c) shows the contact point (point E) between the second contactor 29 and the sample 25.

[0053] FIG. 10A is a diagram showing a junction of dissimilar materials observed by HAADF-STEM (High Angle Annular Dark-Field Scanning Transmission Electron Microscopy). 10B shows the results (amplitude and phase images) of stereo thermal wave measurement, showing the phase and amplitude images at the contact points (points E and F). In the phase and amplitude images measured at the contact point (point E), when the heated point X is located near the contact point (point F) of the first contactor 28, the direction of the heat flow inside the sample 25 is not toward point Y on the extension of the contactor 28, but toward the contact point (point E). This is expected to be because the internal structure of the sample 25 contains defects that create thermal resistance that makes it difficult for heat to flow, such as grain boundaries or vacancies, in the direction parallel to the line connecting the contact points (points E and F). On the other hand, in the phase image measured at the contact point (point F), a concentric phase image centered on the contact point (point F) was obtained, and no heat flow from the contact point (point F) to the contact point (point E) was observed. This is because, in the internal structure of the sample 25, defects that cause thermal resistance that makes it difficult for heat to flow, such as grain boundaries or vacancies, in the direction parallel to the line connecting the contact points (points E and F), do not exist in the direction of point Y on the extension line between the contact point (point F) and the contact 28. In the amplitude image measured at the contact point (point F), a distorted concentric amplitude image was obtained on the side toward the contact point (point E), which suggests the presence of defects such as grain boundaries and vacancies between the contact point (point F) and the contact point (point E).

[0054] Figure 11A shows the amplitude images measured at two points for amplitude ratio analysis, showing the contact point (point E) and the contact point (point F) separately. n is a distance (L E )x, the area where the amplitude of the temperature wave is large near the contact point (point E) of the contactor 29 is wide. n is a distance (L F )y, the region where the amplitude of the temperature wave is large near the contact point (point F) of the first contactor 28 is narrower than the contact point (point E) of the contactor 29. Figure 11B shows an analysis of the amplitude ratio of temperature waves using amplitude image analysis, showing the amplitude ratio of the temperature waves flowing from each heated point to the contact point (point E). When a heated point is located near the contact point (point E), most of the heat flows to the contact point (point E), with almost no heat flow to the contact point (point F). When a heated point is located near the contact point (point F), most of the heat flows to the contact point (point F), with almost no heat flow to the contact point (point E). For the heated points at the corners of sample 25, with the contact point (point F) as the vertex, there is a region of low heat flow at the triangular contact point (point F), and it is expected that some kind of tissue mismatch exists in the linear region near the base of this triangle.

[0055] FIG. 12 is an explanatory diagram of local heat flow analysis using stereo thermal wave measurement. Here, the image is divided into 8x6 grids, and each square is labeled A through H in the top row, I through P in the second row, Q through X in the third row, Y, Z, and a through f in the fourth row, g through n in the fifth row, and o through v in the last row. In the figure, squares O, T, W, a, e, and m are black squares. Squares O, W, e, and m represent four consecutive defects in the vertical direction. Squares T and a represent a single defect.

[0056] α represents the contact point (point E) of the second contactor 29, which is in contact with mass H. β represents the contact point (point F) of the first contactor 28, which is in contact with mass v. (a) shows the case where the heating point is mass H, and the heat flow ratio of α to β is 9.5:0.5. (b) shows the case where the heating point is mass G, and the heat flow ratio of α to β is 9:1. (c) shows the case where the heating point is mass F, and the heat flow ratio of α to β is 8.5:1.5. (d) shows the case where the heating point is mass N, and the heat flow ratio of α to β is 7:3. (e) shows the case where the heating point is mass V, and the heat flow ratio of α to β is 6:4. Next, (f) shows the case where the heating point is mass d, and the heat flow ratio between α and β is 4:6. (g) shows the case where the heating point is mass l, and the heat flow ratio between α and β is 3:7. (h) shows the case where the heating point is mass t, and the heat flow ratio between α and β is 1.5:8.5. (i) shows the case where the heating point is mass u, and the heat flow ratio between α and β is 1:9. (j) shows the case where the heating point is mass v, and the heat flow ratio between α and β is 0.5:9.5. In this way, even if the sample 25 has defects such as voids, grain boundaries, contact interfaces, etc. that inhibit the uniformity of the heat flow direction, the anisotropy of the heat flow direction can be detected.

[0057] The stereo temperature wave measurement device and method of the present invention measure the heat flow direction of a metallic material or a conductive composite material containing a metal by combining a nanoscale heat application method using electron beam irradiation or the like with temperature measurement with nanoscale spatial resolution, and various modifications are conceivable within the scope obvious to those skilled in the art. For example, the stereo temperature wave measurement device and method of the present invention can be combined with conventional electron microscopy methods such as microstructure evaluation and elemental analysis (EDS, EELS), electromagnetic field observation, electrical transport measurement, and stress measurement to simultaneously measure the heat flow direction and perform electromagnetic property and elemental analysis. [Industrial Applicability]

[0058] As described above, the stereo temperature wave measurement device and method of the present invention can be applied to the evaluation of thermal resistance at pores, grain boundaries, and contact interfaces in a sample made of a first metallic material or a conductive composite material containing the first metallic material, and can also be applied to the measurement of the heat flow direction in anisotropic materials and composite materials. [Explanation of symbols]

[0059] 10 Transmission electron microscope (STEM / charged particle beam generator) 12 Electrostatic Shutter 14 Electrostatic Dose Modulator (EDM) 20 Temperature wave generator 21 Samples (insulating materials, ceramics, etc.) 22 Pulsed electron beam 23 Constantan probe (thermocouple) 24 Chromel probe (thermocouple) 25 Sample (first metal material) 25a Thin section 25b Thick wall part 26 Tungsten reference temperature element 27 Sample stage 28 First Contact 29 Second Contact 30, 30a, 30b Lock-in amplifier 40 Signal Processing Unit 42 Signal Switcher 44 Offset and gain control device 50 Electron beam control and image processing system (DigiScan) 60 Analysis computer

Claims

1. Two points (T １ Point (F point), T ２ first and second contacts made of a second metallic material, which contact the first metallic material at a point (point E) and generate a thermoelectric power with respect to the first metallic material; a heating device that heats at least one heating point on the sample using a pulsed electron beam having a predetermined frequency (f); a device for detecting outputs of the first and second contactors in response to a temperature rise at the contact points with the first and second contactors due to heating by the pulsed electron beam of the predetermined frequency (f), and measuring an amplitude component of a temperature wave corresponding to the heating position of the heating point by the predetermined frequency (f), When generating thermoelectromotive forces at the first and second contactors, a portion that holds the sample within a region irradiated with the electron beam is used as a reference junction, and points of contact between the first and second contactors and the sample are used as first and second temperature measuring junctions, The amplitude component (T Ｅ (x), T Ｆ (y)), the amplitude ratio (T Ｅ (x) / (T Ｅ (x) + T Ｆ (y)), the proportion of heat flowing into the contact points (points F and E) is calculated, thereby determining the direction of heat flow in the sample.

2. The amplitude ratio (T Ｅ (x) / (T Ｅ (x) + T Ｆ 2. The stereo temperature wave measuring device according to claim 1, wherein (y) is calculated by the following formula: [Equation 1] where α is the thermal diffusivity, f is the frequency of the electron beam, and x is the distance from the heating point to the second contact point (T ２ Point (Point E)) direction distance (L Ｅ ), y: distance from the heating point to the first contact point (T １ Point (F)) direction distance (L Ｆ )

3. Further, the device includes a device for detecting outputs of the first and second contactors in response to a temperature rise at the contact points with the first and second contactors due to heating by the pulsed electron beam of the predetermined frequency (f), and measuring a phase component of a temperature wave corresponding to the heating position of the heating point by the predetermined frequency (f), The phase component (θ) of the temperature wave generated by the pulsed electron beam is used to determine the distance (L) from the heating point to the contact points (points F and E) of the first and second contactors on the sample. Ｆ , L Ｅ 2. The stereo temperature wave measuring device according to claim 1, wherein the thermal diffusivity (α) between the heating point and the contact point is calculated based on the following equation: α=π / / (θ / L Ｆ ) ２ or α=πf / (θ / L Ｅ ) ２

4. The sample is accommodated in a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM) so that a TEM image or a STEM image can be observed; a heating device that irradiates the focused electron beam onto the heating point is an electron gun of the TEM or STEM; The stereo temperature wave measuring device according to claim 1 .

5. The heating point on the sample is the distance (L Ｆ , L Ｅ 2. The stereo temperature wave measuring device according to claim 1, wherein the heating points are different from each other.

6. 2. The stereo temperature wave measuring device according to claim 1, wherein the predetermined frequency (f) is a plurality of frequencies selected from the range of 1 Hz to 1 MHz.

7. 2. The stereo temperature wave measuring device according to claim 1, wherein the pulsed electron beam of the predetermined frequency (f) has an on-off duty ratio selected from the range of 1:9 to 9:1, and a pulse on-time width selected from the range of 100 ns to 1 sec.

8. 2. The stereo temperature wave measuring device according to claim 1, wherein the first and second contacts are needle-shaped, and the diameter of the tip of the needle-shaped contact is 100 nm or less.

9. 2. The stereo temperature wave measuring device according to claim 1, wherein the second metal material is chromel, constantan, or a metal material that generates a large amount of thermoelectromotive force with respect to the first metal material.

10. 2. The stereo temperature wave measuring device according to claim 1, wherein the thickness of the sample at the first and second contacts and the heated points by the electron beam is thinner than the thickness of a portion of the sample that holds the sample within an area irradiated with the electron beam.

11. 2. The stereo temperature wave measuring device according to claim 1, wherein the measurement timing of the device for measuring the phase component of the temperature wave is a state in which the temperature is oscillating with a small amplitude at a temperature that has risen to a substantially steady state by the pulsed electron beam.

12. Furthermore, it is equipped with an analytical computer, The analysis computer calculates the amplitude component (T Ｅ (x), T Ｆ (y)), the amplitude ratio (T Ｅ (x) / (T Ｅ (x) + T Ｆ (y)), the ratio of the heat flow flowing into the contact points (points F and E) is calculated, thereby determining the heat flow direction of the sample.

12. The stereo temperature wave measuring device according to claim 1.

13. A sample made of a first metal material or a conductive composite material containing the first metal material is provided with first and second contacts (T) made of a second metal material that generate a thermoelectric power to the first metal material. １ Point (F point), T ２ Contact at point E Heating a heating point on the sample using a pulsed electron beam having a predetermined frequency (f), detecting outputs of the first and second contactors in response to a temperature rise at the contact points with the first and second contactors due to heating by the pulsed electron beam of the predetermined frequency (f), and measuring an amplitude component of a temperature wave corresponding to the heating position of the heating point due to the predetermined frequency (f); The amplitude component (T Ｅ (x), T Ｆ (y)), the amplitude ratio (T Ｅ (x) / (T Ｅ (x) + T Ｆ (y)), the ratio of the heat flow flowing into the contact points (points F and E) is calculated, thereby determining the heat flow direction of the sample. Stereo temperature wave measurement method.

14. The amplitude ratio (T Ｅ (x) / (T Ｅ (x) + T Ｆ The stereo temperature wave measurement method according to claim 13, wherein (y)) is calculated by the following formula: [Equation 2] where α is the thermal diffusivity, f is the frequency of the electron beam, and x is the distance from the heating point to the second contact point (T ２ Point (Point E)) direction distance (L Ｅ ), y: distance from the heating point to the first contact point (T １ Point (F)) direction distance (L Ｆ )

15. detecting a plurality of outputs of the first and second contacts in response to a temperature rise of the contact point due to heating by the pulsed electron beam of the predetermined frequency (f), and measuring phase components of temperature waves corresponding to the heating positions of the heating point due to the predetermined frequency (f); The phase component (θ) of the temperature wave generated by the pulsed electron beam is used to determine the distance (L) from the heating point to the contact points (points F and E) of the first and second contactors on the sample. Ｆ , L Ｅ 14. The stereo temperature wave measuring method according to claim 13, wherein the thermal diffusivity (α) between the heating point and the contact point is calculated based on the following equation: α=π / / (θ / L Ｅ ) ２ or α=πf / (θ / L Ｆ ) ２

16. The sample is placed in a TEM or STEM so that a TEM image or a STEM image can be observed; The electron beam is irradiated by an electron gun of the TEM or STEM. The stereo temperature wave measurement method according to claim 13.

17. detecting a plurality of calibration outputs corresponding to the heating positions of the plurality of heating points from the first and second contactors while the sample is released from contact with the first and second contactors; and canceling, by the plurality of calibration outputs, the influence of secondary electrons caused by the irradiation of the electron beam onto the plurality of heating points on the outputs of the first and second contacts. The stereo temperature wave measurement method according to claim 13.

18. 14. The stereo thermal wave measurement method according to claim 13, wherein the heated points on the sample are a plurality of heated points having different distances (L) to the contact points of the first and second contactors on the sample.

19. 14. The stereo temperature wave measuring method according to claim 13, wherein the predetermined frequency (f) is a plurality of frequencies selected from the range of 1 Hz to 1 MHz.

20. 14. The stereo temperature wave measuring method according to claim 13, wherein the pulsed electron beam of the predetermined frequency (f) has an on-off duty ratio selected from the range of 1:9 to 9:1, and a pulse on-time width selected from the range of 100 ns to 1 sec.

21. 21. The stereo temperature wave measuring method according to claim 13, wherein the timing for measuring the phase component of the temperature wave is when the temperature is oscillating with a small amplitude after the temperature has risen to a substantially steady state by the pulsed electron beam.

Images