A solid-liquid system preparation method based on raman scattering and a thermal resistance measurement method thereof

Abstract

The application provides a solid-liquid system preparation and interface thermal resistance measurement method based on Raman scattering, which comprises the following steps: step 1, preparing a substrate with SERS effect; step 2, transferring two-dimensional nanomaterial on the surface of the SERS substrate prepared in step 1, and the thickness of the two-dimensional nanomaterial is not more than 2 nm; step 3, selecting a solution with SERS effect and heat-sensitive effect and combining the solution with the solid part obtained in step 2; and step 4, performing Raman spectrum measurement on the solid-liquid system prepared in step 3 under variable laser power, obtaining the offset amount of the Raman spectrum characteristic peaks on both sides of the solid-liquid interface with the incident laser power by changing the incident power of the Raman laser, and determining the temperature rise of the solid-liquid interface through the offset amount. The measurement type is non-contact measurement, the integrity of the measured sample can be maintained, and different kinds of solid materials can be used for thermal resistance measurement according to actual measurement requirements.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of measuring interface heat transfer thermal resistance at nanoscale, and particularly relates to a solid-liquid system preparation based on Raman scattering and an interface thermal resistance measurement method thereof. BACKGROUND

[0002] The heat dissipation problem of electronic equipment is a key factor restricting its miniaturization and space architecture. The nanoscale interface heat transfer characteristics are important parameters that must be considered in the thermal design and thermal management of electronic systems. Compared with solid-solid interface heat transfer, the nanoscale solid-liquid interface heat transfer has larger thermal resistance and more complex heat transfer mechanism. Therefore, how to design and process low-dimensional solid-liquid systems and realize accurate measurement and effective regulation of interface thermal properties has become the key to a series of experimental researches. The traditional solid-liquid interface thermal resistance measurement method is limited by inherent disadvantages such as sensor size, and cannot be applied to the measurement of nanoscale interface layer characteristic temperature. SUMMARY

[0003] The purpose of the present application is to provide a solid-liquid system preparation and interface thermal resistance measurement method based on Raman scattering, which uses a non-contact in-situ measurement method to study the nanoscale solid-liquid system interface heat transfer characteristics and regulate the property changes under different temperature fields and voltages.

[0004] The technical solution for achieving the purpose of the present application is as follows:

[0005] A solid-liquid system interface thermal resistance measurement method based on Raman scattering, comprising the following steps:

[0006] Step 1, making a substrate with SERS effect;

[0007] Step 2, transferring two-dimensional nanomaterials on the surface of the SERS substrate prepared in step 1, the thickness of the two-dimensional nanomaterials being not more than 2 nm;

[0008] Step 3, selecting a solution with SERS effect and thermal sensitivity effect and combining it with the solid part obtained in step 2;

[0009] Step 4, performing Raman spectrum measurement on the solid-liquid system prepared in step 3 under variable laser power, obtaining the shift amount of the Raman spectrum characteristic peaks on both sides of the solid-liquid interface with the incident laser power, and determining the temperature rise of the solid and liquid interfaces through the shift amount.

[0010] A solid-liquid interface preparation method for interface thermal resistance measurement, comprising the following steps:

[0011] Step 1, making a substrate with SERS effect;

[0012] Step 2, transfer the two-dimensional nanomaterial on the surface of the SERS substrate prepared in step 1, and the thickness of the two-dimensional nanomaterial is not more than 2 nm;

[0013] Step 3, combine the solution with SERS effect and thermal effect with the solid part obtained in step 2.

[0014] Compared with the prior art, the present application has the following advantages:

[0015] (1) The present application is a non-contact measurement method, which does not change the physical and chemical properties of the system before and after measurement, and does not cause any damage to the measured sample.

[0016] (2) The present application can be used to measure different kinds of material substrates, and has strong universality; and can be temperature controlled by changing the temperature of the system. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The flow chart of the method for measuring emissivity and thermal conductivity according to the present application.

[0018] Figure 2 The preparation method for the solid side in the solid-liquid system.

[0019] Figure 3 The schematic diagram of measuring the solid-liquid interface by Raman spectroscopy.

[0020] Figure 4 The silver-coated silicon substrate with a single-layer graphene film.

[0021] Figure 5 The graph of the change of the 2D characteristic peak of graphene at a certain solid-liquid point with laser power under a 50x objective.

[0022] Figure 6 The schematic diagram of the change of the thermal conductivity of the solid-liquid interface with temperature (range average value).

[0023] Figure 7 The fitting relationship between the characteristic peak shift ratio and g / k.

[0024] Figure 8 The temperature change diagram of the solid system before adding liquid in COMSOL simulation (the curve order from top to bottom is the temperature change of graphene, silver and silicon).

[0025] Figure 9 The temperature change diagram of the solid-liquid system after adding liquid in COMSOL simulation (the curve order from top to bottom is the temperature change of graphene, water, silver and silicon). DETAILED DESCRIPTION

[0026] The present application will be further described below in combination with the drawings and specific embodiments.

[0027] The present application is a solid-liquid system preparation method based on Raman scattering and a thermal resistance measurement method thereof, comprising the following steps:

[0028] Step 1, a SERS (Surface Enhanced Raman Scattering) substrate with small surface roughness and strong SERS effect is prepared, and a metal oxide protective layer is covered on the surface thereof by using chemical vapor deposition technology or the like. Whether the deposition layer is present or not can be selected according to actual needs.

[0029] Step 2, a two-dimensional material with different thicknesses is transferred to the surface of the SERS substrate prepared in Step 1. The specific thickness can be changed according to actual measurement requirements, but it should be noted that the total thickness of the two-dimensional material and the deposition protective layer in Step 1 should not exceed 4 nm. The flowcharts of Step 1 and Step 2 are shown in Figure 2

[0030] Step 3, a Raman probe molecule solution with obvious SERS effect and sensitive Raman characteristic peaks changing with temperature is selected and combined with the solid part obtained in Step 2. The solvent of the probe molecule solution can be water or an organic solvent. In addition, a nanoparticle solution with SERS effect can be used instead of the probe molecule solution.

[0031] Step 4, Raman spectrum measurement of the solid-liquid system prepared in Step 3 is performed by changing the laser power. By changing the incident power of the Raman laser, the shift amount of the Raman spectrum characteristic peaks on both sides of the solid-liquid interface with the incident laser power is obtained, and the temperature rise of the solid and liquid interface can be determined by the shift amount. Thereafter, the interface thermal resistance is calculated according to the shift amount. The measurement principle diagram is shown in Figure 3

[0032] Step 5, the interface thermal resistance is calculated based on the shift amount measured in Step 4. The heat transfer equation of the entire solid-liquid system is as follows: for two-dimensional heat conduction in the direction of laser incidence and heat diffusion, when the Raman laser heats the target substrate, the heat conduction equation during heating is:

[0033]

[0034] In formula (1.1), θ(r, τ) is a function of node temperature changing with time τ and distance r, Φ(r, τ) is a function of heat flow changing with time and distance. α is the thermal diffusivity, λ is the thermal conductivity of the material, g is the interface thermal conductivity, r0 is the radius of the laser heating area, τ is the time, r is the distance from the center of the laser heating area on the plane of the solid-liquid system, θ is the node temperature rise, η is the absorption coefficient of the laser, δ is the thickness of the solid-liquid interface, and p0 is the laser power. When the laser continues to heat, the system will reach a steady state, and the influence of time will be ignored. At this time, the steady-state equation set under the Raman laser irradiation is as follows:

[0035] ​​

[0036] Φ(r) is the function of heat flow rate changing with distance. The following needs to use substitution method to solve θ(r), that is, the function of temperature changing with heat transfer direction.

[0037] Let

[0038]

[0039] Where ξ and x are substitution quantities for simplified formula form, and have no actual physical meaning. Therefore, in the following formula, the independent variable r of the original formula is substituted for x according to this substitution relationship. Bringing this into equation (1.2) can obtain the basic heat conduction equation as:

[0040]

[0041] θ(x) is the function of node temperature changing with x, and x0=ξr0. And the boundary condition at this time becomes:

[0042]

[0043] According to the theory of heat transfer, the general solution of θ(x) can be written as:

[0044] θ(x)=C1I0(x)+C2K0(x)+θ * (x) (1.5)

[0045] Where I0(x) is the first kind zero order modified Bessel function, K0(x) is the second kind zero order modified Bessel function, and C1 and C2 are fixed functions with x as the independent variable. In order to express more intuitively, here C1=C1(x), C2=C2(x). And θ * (x) is the particular solution of θ(x), and

[0046] θ * (x)=C1(x)I0(x)+C2(x)K0(x) (1.6)

[0047] C1(x) and C2(x) are functions to be solved with x as the independent variable. Taking the partial derivative of θ * (x) gives

[0048]

[0049]

[0050] Bringing it into equation (1.3) gives:

[0051]

[0052] Because I0'(x) = I1(x), K0'(x) = -K1(x), where I1(x) is the first kind of first order modified Bessel function, -K1(x) is the negative function of the second kind of first order modified Bessel function. So the expression of C1(x) and C2(x) can be obtained as follows:

[0053]

[0054]

[0055] The boundary conditions in equation (1.4) are brought into (1.1.10) and (1.1.11), and the specific values of C1 and C2 can be obtained:

[0056]

[0057]

[0058]

[0059] The overall expression of θ(x) can be obtained by combining the above equations as follows:

[0060]

[0061] Therefore, the interface temperature rise θ m is:

[0062]

[0063] The Raman laser spot for heating is not a perfect regular circle, so the heat source at the interface can be approximated as a circular area of Gaussian heat source heating, and the relationship between the heat flux Q and the spot radius is shown in equation (1.17).

[0064]

[0065] In equation (1.17), η is the absorption coefficient, and p0 is the laser power. Finally, the calculation formula of the interface thermal resistance R m is:

[0066]

[0067] Equation (1.18) cannot be solved directly using mathematical calculation methods, so it is necessary to use the method assisted by heat transfer simulation software to solve the interface thermal resistance by approximate means.

[0068] According to the calculation of the literature: Cai W, Moore A, Chen S, et al. Thermal transport in suspended and supported monolayer graphene grown by chemical vapor deposition [C] / / APS March Meeting Abstracts. APS, 2011, the ratio of the total thermal conductance (the inverse of the interfacial thermal resistance) g to the thermal conductivity k of the two-dimensional material has a unique functional relationship with the ratio of the Raman characteristic peak shift under different magnification microscopes. This point can also be indicated in equation (1.18). The variable on the right side of the equal sign in equation (1.18) is ξ, and the variable on the left side is the temperature rise θ m , ξ is a single function of g / k, and θ m is a single function of the measured characteristic peak shift. By dividing the R m analytical expressions under different magnification objectives, the influence of other variables (such as Q) in the formula can be removed.

[0069] By COMSOL simulation calculation of different solid-liquid systems, the fitting function relationship can be obtained. According to the ratio of the different shifts measured in step 4, corresponding to this determined function relationship, the range of g / k can be obtained, and then the range of the total interfacial thermal conductance g can be calculated.

[0070] Step 6, on the basis of step 5, heat or cool the solid side of the solid-liquid system, and the influence of temperature change on the interfacial thermal resistance of the solid-liquid system can be measured. The interfacial thermal resistance measurement method under variable temperature is the same as that under constant temperature.

[0071] Step 7, molecular dynamics simulation can be performed on the target solid-liquid system outside the experiment and compared with the actual experimental results.

[0072] Example 1

[0073] The above measurement method does not specify any specific measurement object, that is, the two-dimensional material, SERS substrate material and Raman probe molecule solution that meet the above description can be selected. In order to further illustrate the specific process of the measurement method, the following takes the measurement of the interfacial thermal resistance of the solid-liquid system composed of silver-coated silicon, monolayer graphene and sodium carbonate aqueous solution as an example to illustrate the specific measurement process.

[0074] Step 1, use an electron beam evaporation device to coat silver on the surface of a smooth silicon wafer with a thickness of about 100-200 nm to obtain a solid substrate with smooth surface and good SERS (surface enhanced Raman effect) effect.

[0075] Step 2, on the basis of step 1, use ALD (chemical vapor deposition) technology to deposit an aluminum oxide or titanium dioxide deposition layer with a thickness of about 1 nm-2 nm on the silver-plated silicon surface to protect the SERS structure. The presence or absence of this deposition layer can be selected according to actual needs. Then use a transfer method such as etching liquid transfer to transfer a single or multiple layer of graphene on the silver-plated silicon substrate. In this description, a single layer of graphene is taken as an example. The solid substrate is shown in Figure 4 .

[0076] Step 3, select a Raman probe aqueous solution as the liquid part of the solid-liquid system. Traditional crystal violet, acetic acid and other organic molecular aqueous solutions can be used as liquid probes, and inorganic molecular aqueous solutions such as potassium nitrate and sodium carbonate can also be used. In this description, 1 mol / L sodium carbonate aqueous solution is taken as an example.

[0077] Step 4, perform variable power Raman laser measurement on the solid-liquid system composed of silver-plated silicon, single layer of graphene, and sodium carbonate solution prepared in the above steps, to obtain the change in two-dimensional material and liquid Raman characteristic peaks with laser power when the liquid is added and when the liquid is not added. Before adding the liquid, the shift of the graphene characteristic peak under a 50x objective is about 1.28 wave numbers, and the shift under a 100x objective is about 1.72 wave numbers. After adding the liquid, the shift of the graphene characteristic peak under a 50x objective is about 1.09 wave numbers, and the shift under a 100x objective is about 1.51 wave numbers. The liquid characteristic peak has almost no shift. Combined with the fitting curve of the g / k and shift ratio in Figure 6 , the solid-solid interface contact thermal conductivity of all measurement points without adding liquid at room temperature is calculated to be about 10-30 MW·m -2 ·K -1 by using the "g / k" method. After adding the liquid, the solid-liquid contact thermal conductivity of all measurement points is calculated to be about 10-20 MW·m -2 ·K -1 by using the parallel thermal resistance model. COMSOL is used to model and simulate the temperature change of each interface layer of the solid-liquid system, and the interface temperature change before adding the liquid is shown in Figure 8 , and the temperature change after adding the liquid is shown in Figure 9 . In the figure, C represents graphene.

[0078] Step 5, change the temperature of the solid substrate by using an RT series heating stage, and measure that the interface thermal conductivity has little change between 20°C and 80°C. The specific data are shown in Figure 7 .

[0079] The solid-liquid interfacial thermal resistance non-contact measurement method based on Raman laser of the application has wide application range, and can be applied to the thermophysical property measurement of the sodium carbonate solution-graphene-silver-plated silicon system in the embodiment 1, and can also be applied to the thermophysical property measurement of other solid substrates and surface two-dimensional materials (such as copper substrates). The above embodiments and descriptions in the specification only illustrate the principles and technical effects of the application, and various changes and improvements can be made to the application without departing from the basic method of the application, and these changes and improvements all fall within the scope of the application. The scope of protection of the application is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the thermal resistance at the interface of a solid-liquid system based on Raman scattering, characterized in that, The method comprises the following steps: Step 1, preparing a substrate with SERS effect; Step 2, transferring two-dimensional nanomaterials on the surface of the SERS substrate prepared in step 1, and the thickness of the two-dimensional nanomaterials is not more than 2 nm; Step 3, combining a solution with SERS effect and thermal sensitive effect with the solid part obtained in step 2; Step 4, performing Raman spectrum measurement on the solid-liquid system prepared in step 3 by changing laser power, and obtaining the offset amount of the Raman spectrum characteristic peak on both sides of the solid-liquid interface with the incident laser power by changing the incident power of the Raman laser, and the temperature rise of the solid and liquid interface can be determined by the offset amount; The total thermal resistance of the interface is determined by the following calculation formula: where r0 is the radius of the laser heating zone, I0(x) is the zeroth-order modified Bessel function of the first kind, θ * (x) is a particular solution of the function θ(r), θ(r) is a function of the variation of the nodal temperature with r, r is the distance from the center of the laser heating zone on the plane of the solid-liquid system, η is the absorption coefficient for the laser, and p0 is the laser power; Wherein, the intermediate variable x = ξr, and ξ is a coefficient.

2. The method for measuring the thermal boundary resistance at the interface between a solid and a liquid based on Raman scattering according to claim 1, characterized in that, The substrate with SERS effect prepared in step 1 is also covered with a metal oxide protective layer.

3. The method for measuring the thermal boundary resistance at the interface between a solid and a liquid based on Raman scattering according to claim 2, characterized in that, The thickness of the metal oxide protective layer is not more than 2 nm.

4. The method for measuring the thermal boundary resistance at the interface between a solid and a liquid based on Raman scattering according to claim 1, wherein In step 2, a single-layer or multi-layer two-dimensional nanomaterial is transferred on the surface of the SERS substrate by using etching solution transfer method, and the specific steps are as follows: (1) Put the substrate containing nanomaterials into the etching solution; (2) Transfer the nanomaterial film: after the substrate is completely dissolved, the nanomaterial film floating on the surface of the etching solution is captured and the surface etching solution residue is removed by ion water, and the operation is repeated for several times to completely remove the etching solution; (3) Remove PMMA: use the target substrate to fish out the nanomaterial-PMMA film with the surface washed clean of etching solution, and stand the substrate to completely drip off the water; dry the target substrate with the nanomaterial film at room temperature to remove residual water, and then dry it; (4) Repeat the above steps to obtain a SERS substrate with a target number of layers of graphene.

5. A method for preparing a solid-liquid interface for interface thermal resistance measurement, characterized by, The method comprises the following steps: Step 1, preparing a substrate with SERS effect; Step 2, transferring two-dimensional nanomaterials on the surface of the SERS substrate prepared in step 1, and the thickness of the two-dimensional nanomaterials is not more than 2 nm; Step 3, combining a solution with SERS effect and thermal sensitive effect with the solid part obtained in step 2.

6. The solid-liquid interface preparation method for interface thermal resistance measurement according to claim 5, wherein The two-dimensional nanomaterial is a graphene transfer structure with copper foil as the substrate and single-layer graphene fixed by PMMA on the surface, and the preparation method comprises the following steps: (1) Put the substrate graphene small piece into the etching solution: put the graphene small piece with the substrate into the etching solution for etching; (2) Transfer the graphene film: after the substrate is put into the etching solution, the substrate is completely dissolved, and at this time only the graphene film is left in the etching solution; put the silicon piece into the etching solution culture dish, and capture the graphene film floating on the surface of the etching solution; after successful capture, immerse the graphene film in deionized water to remove the surface etching solution residue; use the same method to transfer to clean deionized water for multiple times to completely remove the etching solution; (3) Remove PMMA: use the target substrate to fish out the graphene-PMMA film with the surface washed clean of etching solution in deionized water, and stand the substrate to completely drip off the water; dry the target substrate with the graphene film at room temperature to remove residual water, and then dry it; The PMMA is removed using acetone, and the substrate sheet is then dried and cooled, resulting in a substrate with a single layer of graphene film.

7. The solid-liquid interface preparation method for interface thermal resistance measurement according to claim 5 or 6, characterized by, The step 1 of making the substrate with SERS effect is also covered with a metal oxide protective layer.

8. The solid-liquid interface preparation method for interface thermal resistance measurement according to claim 7, wherein The metal oxide protective layer has a thickness of no more than 2 nm.

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