Method for testing heat conduction performance of diamond ultra-thin structure

Abstract

The present application belongs to the technical field of super-thin diamond heat conduction performance detection, and particularly relates to a method for testing the heat conduction performance of a super-thin diamond structure. The present application fixes the super-thin diamond structure to be tested on a heat sink; on the surface of the super-thin diamond structure to be tested, a calibration laser is used to excite the sample, and by analyzing the linear relationship between the diamond characteristic Raman peak position and the ambient temperature, the temperature coefficient of the super-thin diamond structure to be tested is obtained; on the surface of the super-thin diamond structure to be tested, a heating laser is used to excite the sample, and the thermal conductivity of the super-thin diamond structure to be tested under different ambient temperatures is calculated. The present application tests the heat conduction performance of a super-thin diamond structure based on Raman spectroscopy. This method is a non-contact type testing method, and compared with the 3ω method, it avoids the damage and testing errors caused by the surface process on the sample; compared with the TDTR method, its testing process is relatively simple; and since the testing laser radius is small, this method has an ultra-high spatial resolution.

Description

Technical Field

[0001] This invention belongs to the field of ultrathin diamond thermal conductivity testing technology, specifically relating to a testing method for the thermal conductivity of ultrathin diamond structures. Background Technology

[0002] With the increasing severity of self-heating effects and heat accumulation problems in high-power-density electronic devices, ultrathin diamond structures have attracted widespread attention as heat dissipation structures due to their high thermal conductivity, low thermal diffusivity, and relatively high resistivity. Therefore, to accurately analyze the thermal conductivity (especially in-plane thermal conductivity) of this structure, thermal conductivity testing methods for ultrathin diamond have become a research hotspot. Currently, the most widely used testing methods can be mainly divided into two categories: non-contact testing methods and contact testing methods.

[0003] A representative contact testing method is the 3ω method. Its principle involves depositing metal on the sample surface, designing an electrode structure, and applying an alternating current of a certain frequency to the structure under test. The thermal signal is then fed back as an electrical signal, allowing further analysis of the measured thermal properties. Its advantages include easy signal acquisition and processing; however, its disadvantages include a relatively large thermal penetration depth, making it unsuitable for testing thin films thinner than 10 μm, and the potential for sample damage due to overvoltage. Furthermore, since this testing method requires surface processing, errors in the processing structure may increase the testing error.

[0004] Non-contact testing methods commonly used include Time-Domain Thermal Reflectance (TDTR). This method primarily uses a heating laser beam to heat the sample surface, and simultaneously analyzes the signal fed back from the probe laser beam with the heating laser to obtain a curve showing the change in the sample surface reflectivity over time. Further analysis reveals changes in the sample surface temperature, internal heat transport, and related thermal parameters. This method offers high accuracy and a wide testing range (in-plane thermal conductivity / normal thermal conductivity / interfacial thermal resistance, etc., applicable to both bulk and thin film materials). However, the high difficulty and cost of building the testing system limits its further commercial application. Summary of the Invention

[0005] The purpose of this invention is to provide a method for testing the thermal conductivity of ultrathin diamond structures. The testing method provided by this invention is a non-contact testing method, which has the characteristics of not causing damage to the sample surface during the testing process, simple testing procedure and high spatial resolution.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for testing the thermal conductivity of ultrathin diamond structures, comprising the following steps:

[0008] (1) Take the diamond ultrathin structure to be tested. The shape of the diamond ultrathin structure to be tested is rectangular. Fix the wide side of the diamond ultrathin structure to be tested on the heat sink.

[0009] (2) On the surface of the diamond ultrathin structure to be tested, the sample is excited by a calibration laser under different ambient temperature conditions. The calibration laser power is ≤1mW. The Raman characteristic peak positions of the diamond ultrathin structure to be tested corresponding to different ambient temperatures under the calibration laser excitation conditions are obtained. The ambient temperature is used as the independent variable and the corresponding Raman characteristic peak position is used as the dependent variable for linear fitting to obtain the linear relationship between the peak position of the diamond ultrathin structure to be tested and the ambient temperature. The slope of the linear relationship is the temperature coefficient of the diamond ultrathin structure to be tested.

[0010] (3) On the surface of the diamond ultrathin structure to be tested, the sample is excited by heating laser under different ambient temperatures. The power of the heating laser excitation is ≥15mW. The Raman characteristic peak position of the diamond ultrathin structure to be tested corresponding to different ambient temperatures under the heating laser excitation conditions is obtained. The thermal conductivity of the diamond ultrathin structure to be tested under different ambient temperatures is calculated according to Formula 1. The curve of the thermal conductivity of the diamond ultrathin structure to be tested as a function of ambient temperature is obtained.

[0011]

[0012] In Formula 1: κ is the thermal conductivity of the diamond ultrathin structure under test; A is a constant related to the sample size and laser excitation position; χ is the temperature coefficient of the diamond ultrathin structure under test; n is the laser absorption constant of the diamond ultrathin structure under test; ΔP is the difference between the heating laser power and the calibration laser power; Δω D The difference in the peak position of the Raman characteristic peaks obtained by heating laser and calibration laser respectively under the same ambient temperature conditions.

[0013] Preferably, the thickness of the diamond ultrathin structure to be tested is 10–100 nm; the width of the diamond ultrathin structure to be tested is 0.5–10 μm; and the length of the diamond ultrathin structure to be tested is 2–20 μm.

[0014] Preferably, the linear equation relating the position of the excited Raman characteristic peak of the diamond ultrathin structure to be tested to the ambient temperature is shown in Equation 2:

[0015] ω D =χT+ω0 Formula 2;

[0016] In Formula 2: ω D χ represents the Raman characteristic peak position of the diamond ultrathin structure to be tested, χ is the temperature coefficient of the diamond ultrathin structure to be tested, T is the ambient temperature, and ω0 is the Raman characteristic peak position of the diamond ultrathin structure to be tested at 0K.

[0017] Preferably, at least one wide side of the ultrathin diamond structure to be tested is fixed to the heat sink;

[0018] When only one wide side of the diamond ultrathin structure under test is fixed to the heat sink, and the laser excitation position is the suspended side of the diamond ultrathin structure under test, the parameter A in Formula 1 is calculated by the following Formula 3:

[0019]

[0020] In Formula 3: L is the length of the diamond ultrathin structure to be tested, W is the width of the diamond ultrathin structure to be tested, and h is the thickness of the diamond ultrathin structure to be tested.

[0021] When both wide sides of the diamond ultrathin structure under test are fixed on the heat sink, and the laser excitation position is the surface of the diamond ultrathin structure, the parameter A in Formula 1 is calculated by the following Formula 4:

[0022]

[0023] In Formula 4: L is the length of the diamond ultrathin structure to be tested, W is the width of the diamond ultrathin structure to be tested, h is the thickness of the diamond ultrathin structure to be tested, L1 is the distance from the laser excitation position to the heat sink end with one wide side fixed, and L2 is the distance from the laser excitation position to the heat sink end with the other wide side fixed.

[0024] Preferably, the wavelengths of the calibration laser and the heating laser are 488nm, 532nm, or 632nm, and the corresponding Gaussian radii of the light spots are 207nm, 224nm, or 268nm.

[0025] Preferably, the power of the calibration laser excitation is 0.8 to 1 mW.

[0026] Preferably, the power of the heating laser excitation is 15-30mW.

[0027] Preferably, the heat sink is a thermally conductive material.

[0028] Preferably, the heat sink is made of a metallic material.

[0029] Preferably, in step (1), the fixing is performed by welding the diamond ultrathin structure to be tested onto the heat sink by ion beam deposition of Pt.

[0030] This invention provides a method for testing the thermal conductivity of ultrathin diamond structures, comprising the following steps:

[0031] (1) Take a diamond ultrathin structure to be tested. The shape of the diamond ultrathin structure to be tested is rectangular. Fix the wide side of the diamond ultrathin structure to be tested on a heat sink. (2) On the surface of the diamond ultrathin structure to be tested, use a calibration laser to excite the sample under different ambient temperature conditions. The calibration laser power is ≤1mW. Obtain the Raman characteristic peak position of the diamond ultrathin structure to be tested corresponding to different ambient temperatures under the calibration laser excitation conditions. Perform linear fitting with ambient temperature as independent variable and the corresponding Raman characteristic peak position as dependent variable to obtain the diamond ultrathin structure to be tested. The linear relationship between peak position and ambient temperature, the slope of the linear relationship is the temperature coefficient of the diamond ultrathin structure to be tested; (3) On the surface of the diamond ultrathin structure to be tested, the sample is excited by heating laser under different ambient temperatures, the power of the heating laser excitation is ≥15mW, the Raman characteristic peak position of the diamond ultrathin structure to be tested corresponding to different ambient temperatures under the heating laser excitation conditions is obtained, the thermal conductivity of the diamond ultrathin structure to be tested under different ambient temperatures is calculated according to Formula 1, and the curve of the change of thermal conductivity of the diamond ultrathin structure to be tested with ambient temperature is obtained. Figure 1 and Figure 2 The testing apparatus and process shown in this invention are based on the following testing principle: When only one wide edge is fixed to the heat sink, a laser is focused on the suspended side of the diamond ultrathin structure; when both wide edges are fixed to the heat sink, a laser is focused on the surface of the diamond ultrathin structure. In this case, the surface of the diamond ultrathin structure sample is heated. Because the sample thickness is less than the phonon mean free path of diamond, it is limited by size effects; and except for the heat sink end, the remaining edges of the ultrathin structure are in contact with air, which is not conducive to heat conduction. When only one wide edge is fixed to the heat sink, the heat generated by laser excitation tends to propagate from the excitation point along the horizontal plane of the ultrathin structure to one end of the heat sink; when both wide edges are fixed to the heat sink, the heat generated by laser excitation tends to propagate from the excitation point along the horizontal plane of the ultrathin structure to both ends of the heat sink. Furthermore, since the length of the diamond ultrathin structure under test is much larger than the laser spot size, the heat should propagate radially; simultaneously, the shape of the heat flow wavefront can be considered as a plane parallel to the sample cross-section. This invention obtains the Raman spectrum of the sample by laser excitation. Furthermore, because the diamond lattice spacing changes with ambient temperature, the Raman characteristic peak position of diamond is adjusted by ω. D (At room temperature, it is generally 1332.5cm) -1The Raman characteristic peaks of the diamond also exhibit a shift: as the temperature rises, the peak positions of the Raman characteristic peaks of the diamond under test undergo a redshift. Based on the above testing principle, this invention first measures the curve of the Raman characteristic peak position of the diamond ultrathin structure under test versus the ambient temperature under calibration laser excitation, and performs linear fitting to obtain the temperature coefficient of the diamond under test. In this step, this invention selects a calibration laser with a power ≤1mW for excitation. At this level, the laser power is low, and its influence on the sample surface temperature is minimal, thus avoiding any impact on the calculation of the temperature coefficient of the diamond under test. After obtaining the temperature coefficient of the diamond under test, this invention collects the Raman characteristic peak positions of the diamond ultrathin structure under test under different ambient temperature conditions under heating laser excitation with a power ≥15mW. Then, it uses Formula 1 to obtain the thermal conductivity of the diamond ultrathin structure under test under different ambient temperature conditions, and finally obtains the curve of the thermal conductivity of the diamond ultrathin structure under test changing with ambient temperature. This invention proposes a method for testing the thermal conductivity of diamond ultrathin structures based on Raman spectroscopy. This method is a non-contact testing method. Compared with the 3ω method, it avoids the damage to the sample and testing errors caused by surface processing. Compared with the TDTR method, its testing process is relatively simple. Moreover, due to the small test laser radius, this method has ultra-high spatial resolution. Attached Figure Description

[0032] Figure 1 The apparatus 1 and experimental flowchart used in the test method for the thermal conductivity of diamond ultrathin structures provided by the present invention;

[0033] Figure 2 The apparatus 2 and experimental flowchart used in the test method for the thermal conductivity of diamond ultrathin structures provided by the present invention;

[0034] Figure 3 The thermal conductivity data obtained by measuring different diamond ultrathin structures in the embodiments of the present invention and the diamond thermal conductivity data measured in the literature are shown below.

[0035] Figure 4 This is a linear curve showing the change in the position of the Raman characteristic peak with ambient temperature under calibrated laser excitation in Example 2.

[0036] Figure 5 This is a linear curve showing the change in the position of the Raman characteristic peak with ambient temperature under heated laser excitation in Example 3. Detailed Implementation

[0037] This invention provides a method for testing the thermal conductivity of ultrathin diamond structures, comprising the following steps:

[0038] (1) Take the diamond ultrathin structure to be tested. The shape of the diamond ultrathin structure to be tested is rectangular. Fix the wide side of the diamond ultrathin structure to be tested on the heat sink.

[0039] (2) On the surface of the diamond ultrathin structure to be tested, the sample is excited by a calibration laser under different ambient temperature conditions. The calibration laser power is ≤1mW. The Raman characteristic peak positions of the diamond ultrathin structure to be tested corresponding to different ambient temperatures under the calibration laser excitation conditions are obtained. The ambient temperature is used as the independent variable and the corresponding Raman characteristic peak position is used as the dependent variable for linear fitting to obtain the linear relationship between the peak position of the diamond ultrathin structure to be tested and the ambient temperature. The slope of the linear relationship is the temperature coefficient of the diamond ultrathin structure to be tested.

[0040] (3) On the surface of the diamond ultrathin structure to be tested, the sample is excited by heating laser under different ambient temperatures. The power of the heating laser excitation is ≥15mW. The Raman characteristic peak position of the diamond ultrathin structure to be tested corresponding to different ambient temperatures under the heating laser excitation conditions is obtained. The thermal conductivity of the diamond ultrathin structure to be tested under different ambient temperatures is calculated according to Formula 1. The curve of the thermal conductivity of the diamond ultrathin structure to be tested as a function of ambient temperature is obtained.

[0041]

[0042] In Formula 1: κ is the thermal conductivity of the diamond ultrathin structure under test; A is a constant related to the sample size and laser excitation position; χ is the temperature coefficient of the diamond ultrathin structure under test; n is the laser absorption constant of the diamond ultrathin structure under test; ΔP is the difference between the heating laser power and the calibration laser power; Δω D The difference in the peak position of the Raman characteristic peaks obtained by heating laser and calibration laser respectively under the same ambient temperature conditions.

[0043] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0044] This invention uses a rectangular ultrathin diamond structure to be tested, with its wide side fixed to a heat sink. In this invention, the thickness of the ultrathin diamond structure is preferably 10–100 nm, more preferably 55–85 nm. The width of the ultrathin diamond structure is preferably 0.5–100 μm, more preferably 4–8 μm. The length of the ultrathin diamond structure is preferably 2–20 μm, more preferably 10–15 μm. In a specific embodiment of this invention, the ultrathin diamond structure is preferably fabricated using a focused ion beam (FIB) processing system. The heat sink is preferably a thermally conductive material, more preferably a metallic material, specifically copper. The fixing is preferably achieved by welding the ultrathin diamond structure to the heat sink using ion beam deposition of Pt. In a specific embodiment of this invention, at least one wide side of the ultrathin diamond structure is fixed to the heat sink. The ultrathin diamond structure to be tested is welded to the heat sink along one wide side, or both wide sides of the ultrathin diamond structure to be tested are welded to the heat sink. This invention does not have special requirements regarding the specific implementation process of the ion beam deposition.

[0045] This invention involves exciting the sample with a calibration laser on the surface of the diamond ultrathin structure under test. The calibration laser power is ≤1mW, and the calibration laser excitation is performed under different ambient temperatures. The Raman characteristic peak positions of the diamond ultrathin structure under test, corresponding to different ambient temperatures under the calibration laser excitation conditions, are obtained. A linear fit is performed with different ambient temperatures as the independent variable and the peak positions of the diamond ultrathin structure under test as the dependent variable to obtain a linear curve or linear equation between the peak positions of the diamond ultrathin structure under test and the ambient temperature. The slope of the linear curve or linear equation is taken to obtain the temperature coefficient of the diamond ultrathin structure under test. In this invention, the wavelength of the calibration laser is preferably 488nm, corresponding to a Gaussian spot radius of 207nm. Alternatively, the wavelength of the calibration laser is preferably 532nm, corresponding to a Gaussian spot radius of 224nm. Alternatively, the wavelength of the calibration laser is preferably 632nm, corresponding to a Gaussian spot radius of 268nm. The power of the calibration laser is preferably 0.8~1mW. In a specific embodiment of the present invention, the preferred ambient temperature is -190 to 190°C. The linear equation between the peak position of the excited Raman characteristic peak of the diamond ultrathin structure obtained by the present invention and the ambient temperature is shown in Equation 2:

[0046] ω D =χT+ω0 Formula 2;

[0047] In Formula 2: ω D χ represents the Raman characteristic peak position of the diamond ultrathin structure to be tested, χ is the temperature coefficient of the diamond ultrathin structure to be tested, T is the ambient temperature, and ω0 is the Raman characteristic peak position of the diamond ultrathin structure to be tested at 0K.

[0048] After obtaining the temperature coefficient of the diamond ultrathin structure to be tested, the present invention uses a heated laser to excite the sample on the surface of the diamond ultrathin structure to be tested. The power of the heated laser excitation is ≥15mW, and the heated laser excitation is carried out under different ambient temperatures. The Raman characteristic peak positions of the diamond ultrathin structure to be tested corresponding to different ambient temperatures under the heated laser excitation conditions are obtained. The thermal conductivity of the diamond ultrathin structure to be tested under different ambient temperatures is calculated according to Formula 1, and the curve of the thermal conductivity of the diamond ultrathin structure to be tested as a function of ambient temperature is obtained.

[0049]

[0050] In Formula 1: κ is the thermal conductivity of the diamond ultrathin structure under test; A is a constant related to the sample size and laser excitation position; χ is the temperature coefficient of the diamond ultrathin structure under test; n is the laser absorption constant of the diamond ultrathin structure under test; ΔP is the difference between the heating laser power and the calibration laser power; Δω D The difference in the peak position of the Raman characteristic peaks obtained by heating laser and calibration laser respectively under the same ambient temperature conditions.

[0051] In this invention, at least one wide side of the diamond ultrathin structure to be tested is fixed on a heat sink.

[0052] In this invention, when only one wide side of the diamond ultrathin structure under test is fixed to the heat sink, and the laser excitation position is the suspended side of the diamond ultrathin structure under test, the parameter A in Formula 1 is calculated by the following Formula 3:

[0053]

[0054] In Formula 3: L is the length of the diamond ultrathin structure to be tested, W is the width of the diamond ultrathin structure to be tested, and h is the thickness of the diamond ultrathin structure to be tested.

[0055] In this invention, when both wide sides of the diamond ultrathin structure under test are fixed on the heat sink, and the laser excitation position is the surface of the diamond ultrathin structure, parameter A in formula 1 is calculated by the following formula 4:

[0056]

[0057] In Formula 4: L is the length of the diamond ultrathin structure to be tested, W is the width of the diamond ultrathin structure to be tested, h is the thickness of the diamond ultrathin structure to be tested, L1 is the distance from the laser excitation position to the heat sink end with one wide side fixed, and L2 is the distance from the laser excitation position to the heat sink end with the other wide side fixed.

[0058] In this invention, the wavelength of the heating laser is preferably 488 nm, corresponding to a Gaussian spot radius of 207 nm. Alternatively, the wavelength of the heating laser is preferably 532 nm, corresponding to a Gaussian spot radius of 224 nm. Or, the wavelength of the heating laser is preferably 632 nm, corresponding to a Gaussian spot radius of 268 nm. The power of the heating laser is preferably 15–30 mW, more preferably 18–26 mW, and even more preferably 20–25 mW. In a specific embodiment of this invention, the ambient temperature is preferably -190–190°C.

[0059] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] Two types of diamonds with different impurity contents were selected: brown diamond and colorless diamond, with the impurity content in brown diamond being greater than that in colorless diamond. FIB processing was used to obtain ultrathin diamond samples for testing. The brown diamond ultrathin sample is designated as brown sample 1. Figure 3 and Figure 4 The colorless ultrathin diamond structure to be tested (Brown) is designated as colorless sample 2. Figure 3 and Figure 5 The brown sample 1 and the colorless sample 2 have a length of 10-15 μm, a width of 4-8 μm, and a thickness of 55-85 nm.

[0062] Example 2

[0063] according to Figure 1 The test structure diagram shows that brown sample 1 is welded to a copper grid by ion beam deposition of platinum (Pt).

[0064] like Figure 1 As shown, at ambient temperatures of 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, and 190℃, a laser (wavelength 488nm, 532nm, or 632nm, Gaussian radius of focused spot 207nm, 224nm, or 268nm, power P1 of 1mW) was focused on the suspended side of brown sample 1. The dimensional parameter A was calculated to be 14~68 / μm, and the Raman characteristic peak position ω of brown sample 1 at different ambient temperatures was collected. D1 With temperature as the independent variable, the peak position ω of the Raman characteristic peak of brown sample 1 was used as the reference value. D1Using [variable name] as the dependent variable, a linear fit was performed to obtain the linear curve of the Raman characteristic peak position changing with ambient temperature, as shown below. Figure 3 As shown, by taking the slope of the linear curve or linear equation, the temperature coefficient χ of brown sample 1 is obtained as -0.0135 / (cmK).

[0065] Raman characteristic peak positions ω of brown sample 1 were collected at ambient temperatures of 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, and 190℃, respectively, using lasers (wavelengths of 488nm, 532nm, or 632nm; Gaussian radii of the focused spot of 207nm, 224nm, or 268nm; power P2 of 15mW). D2 Calculate ΔP = P2 - P1, and Δω under different ambient temperatures. D =ω D2 -ω D1 Then, the size parameters A, laser absorption constant n (0.5), temperature coefficient χ, ΔP and Δω of the brown sample 1 were determined. D Substituting into Formula 1, the thermal conductivity of brown sample 1 under various ambient temperature conditions is obtained.

[0066]

[0067] Then, with the thermal conductivity of brown sample 1 as the dependent variable and temperature as the independent variable, a curve showing the change in thermal conductivity of brown sample 1 with temperature was established, as follows: Figure 2 The sample with the icon "Brown" in the image.

[0068] Example 3

[0069] according to Figure 1 The test structure diagram shows that colorless sample 2 is welded to a copper grid by ion beam deposition of platinum (Pt) along one wide side.

[0070] like Figure 1As shown, the ambient temperatures were -190℃, -180℃, -170℃, -160℃, -150℃, -130℃, -120℃, -110℃, -100℃, -90℃, -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, and 1 At 20℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, and 190℃, lasers (wavelengths 488nm, 532nm, or 632nm; Gaussian radii of the focused spot 207nm, 224nm, or 268nm; power P1 of 1mW) were focused on the suspended side of colorless sample 2. The size parameter A = 14~68 / μm was calculated, and the Raman characteristic peak position ω of colorless sample 2 at different temperatures was collected. D1 With temperature as the independent variable, the peak position ω of the Raman characteristic peak of colorless sample 2 was used as the criterion. D Using [the variable] as the dependent variable, a linear fit was performed to obtain the linear curve of the Raman characteristic peak position changing with temperature, as shown below. Figure 4 As shown, by taking the slope of the linear curve or linear equation, the temperature coefficient χ = ​​-0.0142 / (cmK) of the colorless sample 2 is obtained.

[0071] The results were obtained at ambient temperatures of -190℃, -180℃, -170℃, -160℃, -150℃, -130℃, -120℃, -110℃, -100℃, -90℃, -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, and 100℃ respectively. At 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, and 190℃, a laser (wavelength 488nm, 532nm, or 632nm, Gaussian radius of focused spot 207nm, 224nm, or 268nm, power P2 of 30mW) was used to focus on the surface of colorless sample 2, and the Raman characteristic peak position ω of colorless sample 2 at the above ambient temperatures was collected. D2 Calculate ΔP = P2 - P1, and Δω under different ambient temperatures. D =ω D2 -ω D1 Then, the size parameters A (14–68 μm), laser absorption constant n (0.9), temperature coefficient χ, ΔP, and Δω of the colorless sample 2 were determined. D Substituting into Formula 1, the thermal conductivity of colorless sample 2 under various ambient temperature conditions is obtained.

[0072]

[0073] Then, with the thermal conductivity of colorless sample 2 as the dependent variable and ambient temperature as the independent variable, a curve showing the change in thermal conductivity of colorless sample 2 as a function of ambient temperature was established, as follows: Figure 2 The sample with the icon "Colorless" in the image.

[0074] Depend on Figure 2 It can be seen that at room temperature, the thermal conductivity of brown sample 1 is relatively low, at 1204±686W / mK; the thermal conductivity of colorless sample 2 is relatively high, at 2192±793W / mK; and as the temperature increases, in the non-low temperature range, the thermal conductivity of all three samples decreases with the increase of temperature, while in the low temperature range, the thermal conductivity can be seen to first increase and then decrease with the increase of temperature. Figure 2 The icon in the figure, "type II," represents the thermal conductivity of type II diamond as a function of temperature, as provided in reference 1 (Balandin, Alexander A. Thermal properties of graphene and nanostructured carbon materials.[J]. Nature Materials, 2011.DOI:10.1038 / nmat3064.). Figure 2 The icon in the image is “N free”, which is from reference 2(E). Wild C,W.Müller-Sebert, et al. Thermal conductivity of CVD diamond films: High-precision, temperature-resolved measurements[J]. Diamond & Related Materials, 1996, 5(6-8): 688-692.DOI:10.1016 / 0925-9635(95)00390-8.) The curve of thermal conductivity of nitrogen-doped diamond as a function of temperature was measured. Figure 2 The icon in the figure, labeled "N admixture," represents the thermal conductivity of nitrogen-doped diamond as a function of temperature, as measured in Reference 2. By comparing the test results obtained in this invention with those obtained using the methods reported in the aforementioned literature, the data and thermal conductivity trends provided by this invention are consistent with those in the literature, demonstrating the reliability of the test method provided by this invention.

[0075] As can be seen from the above embodiments, the thermal conductivity testing method based on Raman spectroscopy provided by the present invention is a non-contact testing method. Compared with the 3ω method, it avoids the damage to the sample and testing errors caused by surface processing. Compared with the TDTR method, its testing process is relatively simple.

[0076] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for testing the thermal conductivity of a diamond ultrathin structure, characterized in that, Includes the following steps: (1) Take the diamond ultrathin structure to be tested. The shape of the diamond ultrathin structure to be tested is rectangular. Fix the wide side of the diamond ultrathin structure to be tested on the heat sink. The thickness of the diamond ultrathin structure to be tested is 10~100nm. (2) On the surface of the diamond ultrathin structure to be tested, the sample was excited by a calibration laser under different ambient temperature conditions. The calibration laser power was ≤1mW. The Raman characteristic peak positions of the diamond ultrathin structure to be tested corresponding to different ambient temperatures under the calibration laser excitation conditions were obtained. With ambient temperature as the independent variable and the corresponding Raman characteristic peak position as the dependent variable, a linear fit was performed to obtain the linear relationship between the peak position of the diamond ultrathin structure to be tested and the ambient temperature. The slope of the linear relationship is the temperature coefficient of the diamond ultrathin structure to be tested. The linear equation between the excitation Raman characteristic peak position of the diamond ultrathin structure to be tested and the ambient temperature is shown in Formula 2. Formula 2; In formula 2, ω D is the Raman characteristic peak position of the diamond ultrathin structure to be measured, χ is the temperature coefficient of the diamond ultrathin structure to be measured, T is the ambient temperature, and ω0 is the Raman characteristic peak position of the diamond ultrathin structure to be measured at 0K. (3) On the surface of the diamond ultrathin structure to be tested, the sample is excited by heating laser under different ambient temperatures. The power of the heating laser excitation is ≥15mW. The Raman characteristic peak position of the diamond ultrathin structure to be tested corresponding to different ambient temperatures under the heating laser excitation conditions is obtained. The thermal conductivity of the diamond ultrathin structure to be tested under different ambient temperatures is calculated according to Formula 1. The curve of the thermal conductivity of the diamond ultrathin structure to be tested as a function of ambient temperature is obtained. Official 1; In Formula 1: κ is the thermal conductivity of the diamond ultrathin structure to be tested, A is a constant related to the sample size and laser excitation position, χ is the temperature coefficient of the diamond ultrathin structure to be tested, and n is the laser absorption constant of the diamond ultrathin structure to be tested. P is the difference between the heating laser power and the calibrated laser power; ω D The difference in the peak position of the Raman characteristic peaks obtained by excitation with a heating laser and a calibration laser under the same ambient temperature conditions; At least one wide side of the diamond ultrathin structure to be tested is fixed to a heat sink; When only one wide side of the diamond ultrathin structure under test is fixed to the heat sink, and the laser excitation position is the suspended side of the diamond ultrathin structure under test, the parameter A in Formula 1 is calculated by the following Formula 3: Official 3; In Formula 3: L is the length of the diamond ultrathin structure to be tested, W is the width of the diamond ultrathin structure to be tested, and h is the thickness of the diamond ultrathin structure to be tested; When both wide sides of the diamond ultrathin structure under test are fixed on the heat sink, and the laser excitation position is the surface of the diamond ultrathin structure, the parameter A in Formula 1 is calculated by the following Formula 4: Official 4; In Formula 4: L is the length of the diamond ultrathin structure to be tested, W is the width of the diamond ultrathin structure to be tested, h is the thickness of the diamond ultrathin structure to be tested, L1 is the distance from the laser excitation position to the heat sink end with one wide side fixed, and L2 is the distance from the laser excitation position to the heat sink end with the other wide side fixed.

2. The test method according to claim 1, characterized in that, The width of the diamond ultrathin structure to be tested is 0.5~10μm; the length of the diamond ultrathin structure to be tested is 2~20μm.

3. The test method according to claim 1, characterized in that, The wavelengths of the calibration laser and the heating laser are 488nm, 532nm, or 632nm, and the corresponding Gaussian radii of the light spots are 207nm, 224nm, or 268nm.

4. The test method according to claim 1 or 3, characterized in that, The power of the calibrated laser excitation is 0.8~1mW.

5. The test method according to claim 1 or 3, characterized in that, The power of the heating laser excitation is 15~30mW.

6. The test method according to claim 1, characterized in that, The heat sink is made of a thermally conductive material.

7. The test method according to claim 6, characterized in that, The heat sink is made of a metallic material.

8. The test method according to claim 1, characterized in that, In step (1), the fixing is: welding the diamond ultrathin structure to be tested onto the heat sink by ion beam deposition of Pt.

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