A method for controlling interface thermal conductivity based on coupling of interface commensurability and normal load

Abstract

The present invention relates to a method for regulating interface thermal conductivity based on the coupling of interface commensurability and normal load, and the method comprises the following steps: (1) establishing a molecular dynamics heat transfer model; (2) performing simulation and processing data: (1) determining the dependence of interface thermal conductivity on the mismatch angle; (2) revealing the intrinsic reasons why interface commensurability affects interface thermal conductivity; (3) determining the influence of state density on heat transport of interfaces with different commensurabilities; (4) obtaining the relationship between the change curve of interface thermal conductivity and normal load under different commensurabilities; (5) revealing the intrinsic mechanism of normal load affecting interface thermal conductivity; (6) determining the influence of interface thermal conductivity on heat under different interface commensurability and normal load. Based on the study of interface commensurability and normal load on energy and heat transport of silicon / silicon interface, the present invention provides an important basis for understanding the internal mechanism of heat transfer of solid materials with different contact interfaces and finding an effective method for controlling interface thermal conductivity.

Description

Technical Field

[0001] The present invention relates to the field of molecular dynamics technology, and in particular to an interface thermal conductivity control method based on the coupling of interface commensurability and normal load. Background Art

[0002] Regulating and controlling interfacial heat transfer in nanodevices is critical for applications such as thermal management and thermal protection. It is well known that heat conduction in semiconductor nanostructures is mainly contributed by phonons, and the performance of nanodevices usually depends on how the system dissipates heat. At the same time, the development of nanotechnology has increased the interface density of devices. Due to the high spatial density of the contact surface, the heat flow through the interface will directly make phonon focusing more likely to occur at the interface, resulting in device failure or damage. The high-density scattering at the interface leads to a significant obstruction of phonon transport. Heat transfer caused by phonon scattering at the semiconductor interface can also have an adverse effect on the performance and reliability of the device. Therefore, scientists have tried to solve the problem of device damage caused by excessive temperature by enhancing heat transfer between contact surfaces or improving the efficiency of heat conduction at the interface.

[0003] With the continuous development of interfacial heat transport theory, molecular dynamics (MD) and modern quantum simulation currently occupy the mainstream position. Non-equilibrium MD simulation is the most direct method to explore interfacial heat transport. In recent years, more and more scholars have paid attention to revealing the intrinsic mechanism of interfacial heat transfer and various methods of enhancing interfacial thermal conductivity (ITC). Chen et al. used MD simulation to study the heat transport of graphene / h-BN interface. The results showed that heat gradually flowed from the single-layer domain to the multilayer domain, resulting in a significant thermal rectification effect. At the same time, Liu's work found that the graphene / h-BN heterostructure has a fairly high ITC, which is one order of magnitude higher than the ITC of metal and graphene. Polanco et al. reported that adding interatomic mixtures between perfect contact surfaces will increase the ITC by 10% to 20%. With the help of modern quantum transport theory, Zhou et al. discussed a variety of effects that significantly affect interfacial heat transport, including interfacial chemical bond formation, lattice orientation, substrate and atomic mass ratio. In addition, related studies have shown that the heat transport characteristics between contact surfaces are related to interfacial bonds and phonons. English et al. proposed a method to regulate ITC at solid / solid interfaces with mismatched vibrational properties. Chang et al. studied the phonon transport mechanism at the Cu-diamond interface and demonstrated that the vibrational matching of interfacial bonds is more important than the vibrational matching of phonons for improving the thermal conductivity of the Cu / diamond interface. Sun et al. reported the interfacial heat transport properties between boron compounds and different substrates Si and SiC. The results showed that ITC is related to the overlap of the phonon state density between the two interface materials, and the matching degree of the phonon state density plays a decisive role in interfacial heat transport.

[0004] The interaction of the interfacial potential between two heat transfer materials can also affect the heat transport process of phonons at the interface. Yu et al. proposed a mechanism to enhance phonon transport and found that Van der Waals (vdW) potential constraints reduced the thermal displacement of atoms, thereby reducing phonon scattering and promoting heat transport. Chen et al. studied heat conduction in asymmetric graphene / h-BN heterostructures, and the results showed that the strength of the interlayer potential has a great influence on the coupling of in-plane and out-of-plane phonons in graphene / h-BN vdW heterostructures. In addition, Wei et al. discussed the heat transfer of hard-soft interfaces, and the results showed that stronger bond energy attracts soft molecules to the hard surface, resulting in more efficient interfacial energy transfer. Bi et al. used MD simulation to study the heat transport of symmetric and asymmetric solid / solid interfaces and found that the interface thermal resistance of the symmetric interface decreased significantly with increasing temperature in the temperature range of 20~70K.

[0005] Silicon (Si) is the most widely used semiconductor material in the world and is also the base material for manufacturing chips. Due to the anisotropy of the lattice arrangement on the silicon surface, the heat transfer interface of silicon-based materials is prone to form commensurate or non-commensurate contact conditions. However, the impact of different commensurate contact interfaces on heat transfer efficiency is still unclear. Therefore, it is extremely important to reveal the intrinsic mechanism of phonon heat transport at the Si / Si interface under different contact conditions. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide an interface thermal conductivity control method based on the coupling of interface commensurability and normal load.

[0007] In order to solve the above problems, the present invention provides a method for controlling interface thermal conductivity based on coupling of interface commensurability and normal load, comprising the following steps:

[0008] (1) Establish a molecular dynamics heat transfer model consisting of a hot area and a cold area of ​​silicon / silicon, directly change the mismatch state of the interface by rotating the hot area, and apply a spring in the z direction of the hot area to apply a normal load to the heat transfer system;

[0009] The heat region comprises a heat transfer atomic zone I, a heat source and a rigid body layer; each atom in the heat region is provided with a spring in the x, y and z directions; and periodic boundary conditions are provided in the x and y directions;

[0010] The cold region includes a fixed wall, a cold source and a heat transfer atomic zone II;

[0011] A heat transfer interface is formed between the heat transfer atomic region I and the heat transfer atomic region II;

[0012] ⑵Execute simulation and process data:

[0013] ① Taking the mismatch angle as 0~45°, the heat source and cold source temperatures are set to 320K and 280K respectively, and comparing the interface thermal conductance under different mismatch angles to determine the dependence of the interface thermal conductance on the mismatch angle;

[0014] ② Taking the mismatch angle of 0~45°, the heat source and cold source temperatures are set to 320K and 280K respectively, and comparing the interfacial distance, Lennard-Jones (LJ) potential energy and force constant under different mismatch angles to reveal the intrinsic reason why the interface commensurability affects the interface thermal conductivity;

[0015] ③ Taking the mismatch angle as 0° and 45°, compare the phonon state density under commensurate and incommensurate states to determine the effect of state density on heat transport at interfaces with different commensurate properties;

[0016] ④ Taking the normal load as 0~50nN, the heat source and cold source temperatures are set to 320K and 280K respectively, the interface temperature difference, heat flow and interface thermal conductivity under different normal loads and interface commensurability are calculated, and then the relationship between the change curve of interface thermal conductivity and normal load under different commensurability is obtained;

[0017] ⑤ Taking the normal load as 0~50nN, the heat source and cold source temperatures are set to 320K and 280K respectively, and calculating the interfacial distance, Lennard-Jones (LJ) potential energy and force constant under different normal loads and interface commensurability to reveal the intrinsic mechanism of the normal load affecting the interfacial thermal conductivity;

[0018] ⑥ Take the mismatch angle as 0~45° and the normal load as 0~30nN, calculate the total heat absorbed by the cold source during the heat transfer process, and determine the influence of interface thermal conductivity coupled with different interface commensurability and normal load on the heat.

[0019] In the step (1), the temperature of the heat source is 320K and the temperature of the cold source is 280K.

[0020] The simulation and data processing in step (2) also include: taking the mismatch angle as 0° and 45°, the normal load as 15 nN, comparing the phonon state density under the commensurate and non-commensurate states, and determining the intrinsic mechanism of the influence of the state density on the thermal transport of interfaces with different commensurate properties.

[0021] The simulation and data processing in step (2) also includes: taking the normal load as 0~50nN, setting the heat source and cold source temperatures to 320K and 280K respectively, calculating the interface temperature difference, heat flow and interface thermal conductivity under different normal loads and interface commensurability, and then obtaining the change curve relationship between the interface thermal conductivity and the normal load under different commensurability, and determining the influence of the normal load on the interface thermal conductivity.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The present invention takes silicon / silicon as the research object, first establishes a molecular dynamics heat transfer model, and then runs the model under different interface commensurabilities and normal loads. By calculating the interface thermal conductance under different commensurabilities and normal loads and processing and analyzing, the dependence of silicon / silicon interface thermal conductance on interface commensurability and normal load is determined: in the transition process from commensurability to incommensurability, the interface thermal conductance gradually decreases. This is because the reduced force constant in the commensurability interface reduces the transmittance of phonons, inhibits the excitation of high-frequency phonons, causes the phonon spectrum to redshift, and thus weakens the interface thermal conductance; in addition, the increased normal load will significantly increase the interface thermal conductance in commensurability and incommensurability interfaces. The inherent reason is that the interlayer distance decreases with the increase of normal load, thereby enhancing the interface potential energy and force constant, and improving the interface heat transfer efficiency.

[0024] 2. The present invention determines the dependence of the interface thermal conductivity on the mismatch angle by calculating the interface thermal conductivity under different commensurability interface mismatch angles.

[0025] 3. The present invention reveals the intrinsic reason why interface commensurability affects interface thermal conductivity by statistically analyzing the inter-interface distance, Lennard-Jones (LJ) potential energy and force constant under different mismatch angles: the reduction of the force constant in the incommensurable interface reduces the transmittance of phonons, and the excitation of high-frequency phonons is suppressed, resulting in a red shift of the phonon state density, thereby weakening the interface thermal conductivity.

[0026] 4. The present invention determines the influence of the state density on the heat transport of interfaces with different commensurability by extracting the phonon state density under commensurate and incommensurate contact states.

[0027] 5. The present invention shows the relationship between the change curve of interface thermal conductivity and normal load under different commensurabilities by characterizing the interface temperature difference, heat flow and interface thermal conductivity under different normal loads and interface commensurabilities.

[0028] 6. The present invention reveals the intrinsic mechanism by which normal load affects interfacial thermal conductivity by analyzing the inter-interface distance, Lennard-Jones (LJ) potential energy and force constant under different normal loads and interface commensurability: When no normal load is applied, the heat transfer system is in the lowest energy configuration; once a normal load is applied, the system will be dragged away from the potential energy valley, and the increased normal load causes the interlayer potential energy and force constant to increase, making the interlayer interaction harder, thereby enhancing the heat transfer capacity at the interface.

[0029] 7. The present invention determines the influence of different interface commensurability and interface thermal conductivity under normal load on heat by extracting the total heat absorbed by the cold source during the heat transfer process.

[0030] 8. The present invention regulates interfacial heat transport by changing the interfacial commensurability and applying normal loads, which provides an important basis for understanding the internal mechanism of heat transfer of solid materials with different contact interfaces and finding effective methods to control interfacial thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0032] Figure 1 : is the molecular dynamics model of the silicon / silicon interface heat transfer system in the embodiment of the present invention. Wherein: a represents the heat transfer model of the entire system, and b represents the hot area in the heat transfer model (different mismatch angles are obtained by applying normal loads through springs and rotating the hot area).

[0033] Figure 2 It is an enlarged schematic diagram of the commensurate and incommensurate interfaces in the embodiment of the present invention. Among them: a and b are the front views of the commensurate and incommensurate interfaces respectively; c and d are the top views of the commensurate and incommensurate interfaces respectively.

[0034] Figure 3 The dependence of the interface thermal conductivity on the mismatch angle in an embodiment of the present invention (a) and the interface thermal conductivity of the hot area and the cold area at different sizes (b).

[0035] Figure 4 Schematic diagram of the calculation process of extracting the interface temperature difference between the hot area and the cold area using the SW potential (a) and the Tersoff potential (b) in the embodiment of the present invention.

[0036] Figure 5 1 is the functional relationship between the inter-interface distance (a), Lennard-Jones potential energy (b) and force constant (c) and the mismatch angle in the embodiment of the present invention.

[0037] Figure 6 1 is the phonon state density distribution under commensurate and incommensurate states in an embodiment of the present invention.

[0038] Figure 7 1 and 10 are curves showing the interface temperature difference (a), heat flux (b) and interface thermal conductivity (c) under different contact conditions as a function of normal load in an embodiment of the present invention.

[0039] Figure 8 1 is the dependence of the inter-interface distance (a), Lennard-Jones potential energy (b) and force constant (c) on the normal load under different contact states in the embodiment of the present invention.

[0040] Fig. 9 1 is a curve showing the change of heat absorbed by the cold source under different mismatch angles (a) and normal loads (b) in the embodiment of the present invention. DETAILED DESCRIPTION

[0041] A method for controlling interface thermal conductivity based on coupling of interface commensurability and normal load comprises the following steps:

[0042] (1) A molecular dynamics heat transfer model consisting of a hot area and a cold area of ​​silicon / silicon (Si / Si) was established. The mismatch state of the interface was directly changed by rotating the hot area, and a spring was applied in the z direction of the hot area to apply a normal load to the heat transfer system.

[0043] The hot zone includes the heat transfer atomic zone I, the heat source and the rigid body layer; each atom in the hot zone is set with springs in the x, y and z directions; among them: the springs in the x and y directions are used to ensure that the interface state will not return to the common contact after the interlayer rotation angle changes; the spring in the z direction will adjust the force between the contact surfaces, and applying normal loads through the springs can avoid directly applying force to the atoms and causing them to be damaged. Set periodic boundary conditions in the x and y directions;

[0044] The cold region includes fixed walls, cold sources and heat transfer atomic zone II.

[0045] A heat transfer interface is formed between heat transfer atomic zone I and heat transfer atomic zone II.

[0046] The temperature of the heat source is 320K and the temperature of the cold source is 280K.

[0047] ⑵Execute simulation and process data:

[0048] ① Taking the mismatch angle as 0~45°, the heat source and cold source temperatures are set to 320K and 280K respectively, and comparing the interface thermal conductance under different mismatch angles to determine the dependence of the interface thermal conductance on the mismatch angle;

[0049] ② Taking the mismatch angle of 0~45°, the heat source and cold source temperatures are set to 320K and 280K respectively, and comparing the interfacial distance, Lennard-Jones (LJ) potential energy and force constant under different mismatch angles to reveal the intrinsic reason why the interface commensurability affects the interface thermal conductivity;

[0050] ③ Taking the mismatch angle as 0° and 45°, compare the phonon state density under commensurate and incommensurate states to determine the effect of state density on heat transport at interfaces with different commensurate properties;

[0051] ④ Taking the normal load as 0~50nN, the heat source and cold source temperatures are set to 320K and 280K respectively, the interface temperature difference, heat flow and interface thermal conductivity under different normal loads and interface commensurability are calculated, and then the relationship between the change curve of interface thermal conductivity and normal load under different commensurability is obtained;

[0052] ⑤ Taking the normal load as 0~50nN, the heat source and cold source temperatures are set to 320K and 280K respectively, and calculating the interfacial distance, Lennard-Jones (LJ) potential energy and force constant under different normal loads and interface commensurability to reveal the intrinsic mechanism of the normal load affecting the interfacial thermal conductivity;

[0053] ⑥ Take the mismatch angle as 0~45° and the normal load as 0~30nN, calculate the total heat absorbed by the cold source during the heat transfer process, and determine the influence of interface thermal conductivity coupled with different interface commensurability and normal load on the heat.

[0054] The method of performing simulation and processing data in the present invention also includes one of the following:

[0055] Taking the mismatch angle as 0° and 45° and the normal load as 15nN, the phonon state density under commensurate and incommensurate states is compared to determine the intrinsic mechanism of the influence of state density on thermal transport at interfaces with different commensurabilities.

[0056] The normal load is set to 0~50nN, and the temperatures of the heat source and cold source are set to 320K and 280K respectively. The interface temperature difference, heat flux and interface thermal conductivity under different normal loads and interface commensurability are calculated, and then the relationship between the change curve of interface thermal conductivity and normal load under different commensurability is obtained to determine the influence of normal load on interface thermal conductivity.

[0057] Embodiment The present invention takes silicon / silicon system as the research object and explores the research method of interface commensurability and normal load regulation of interface heat transport mechanism.

[0058] The present invention uses a molecular dynamics model to reveal the intrinsic mechanism that affects heat transport at a silicon / silicon interface under different interface commensurabilities and normal loads: in the transition from commensurability to non-commensurability, the reduced force constant reduces the phonon transmittance, suppresses the excitation of high-frequency phonons, causes the phonon state density to redshift, and thus weakens the interface thermal conductivity; the applied normal load will significantly increase the interface thermal conductivity, the intrinsic reason being that the normal load reduces the interface interlayer distance, strengthens the interface potential energy, increases the force constant, and thus enhances the interface thermal conductivity; in the commensurate state, the total heat absorbed by the system cold source will become larger, which means that stronger interface thermal conductivity will lead to more heat transfer at the interface.

[0059] The specific process is as follows:

[0060] (1) Establishing molecular dynamics model

[0061] like Figure 1 As shown, an interfacial heat transport and heat transfer system consisting of a hot area and a cold area is established to explore the intrinsic mechanism of heat transport at the silicon / silicon interface.

[0062] The heat transfer calculation domain contains 54,000 atoms, and the length of the hot and cold regions along the x, y and z axes (heat transport direction) is 8.15 nm. The regions on both sides of the z axis are set as rigid bodies, among which: the rigid body layer in the cold region is set as a fixed wall. The two layers of regions adjacent to the rigid body along the z axis are set as heat sources and cold sources respectively, and the other atomic layers are heat transfer regions. The Berendsen thermostat achieves temperature control through heat exchange between the heat transfer region and the constant temperature region, and stably controls the temperature of the heat source and cold source at 320K and 280K respectively. During the heat exchange process, heat is released from the heat source and then absorbed by the cold source through the heat transfer region.

[0063] A microcanonical ensemble (NVE) that keeps the number of atoms, volume, and energy constant is selected and applied to all heat transfer calculations. The system is initially balanced in the NVE ensemble for 100 ps. After the system reaches thermal equilibrium, a heat transfer calculation is performed for 500 ps to obtain a constant heat flux density and stable temperature distribution at the Si / Si interface.

[0064] Two sets of springs are applied to each atom in the hot region in the x and y directions, respectively, with stiffness coefficients defined as k x and k y , to ensure that the interface contact state will not return to commensurate contact after the mismatch angle changes. The spring in the z direction is used to adjust the force between the contact surfaces. Applying a normal load through the spring can avoid directly applying force to the atoms and causing them to be damaged. It is worth noting that the silicon surface exhibits 90° symmetry, so the 45° mismatch angle between the hot area and the cold area can characterize a completely non-commensurate interface. For ease of understanding, the enlarged images of the commensurate interface (mismatch angle of 0°) and the non-commensurate interface (taking the mismatch angle of 45° as an example) are shown in Figure 2 The so-called commensurate interface means that the atomic structures on the contact surface are completely consistent, and the atomic lattice structures of the interface match and overlap, such as Figure 2 a and 2c. The incommensurate interface characterizes the mismatch of the interface atoms, that is, the atomic structure between the contacting surfaces becomes different, and the lattice structure mismatch no longer overlaps, as shown in Figure 2 b and 2d. Figure 2 c and 2d are top views of the commensurate and incommensurate interfaces, respectively).

[0065] The interaction between the hot and cold regions is described by the Lennard-Jones (LJ) potential, with a potential well depth of eV, the atomic distance when the interaction potential between two atoms is zero Å. The cutoff radius for all LJ potentials is 2.6 (9.9476 Å), beyond which the interaction between atoms on the contact surface will be neglected. The Stillinger-Weber potential is used to characterize the covalent bond interaction potential between any two silicon atoms in the hot or cold region, and the lattice constant of silicon is selected from the optimized value of 5.431 Å.

[0066] Eight atoms were selected from the contact surfaces of the hot and cold regions to calculate the interfacial distance and extract the phonon state density. Finally, the hot region was directly rotated to change the interface mismatch angle, and a spring was applied in the z direction to apply a normal load to the heat transfer system.

[0067] (2) Determine the effect of interface commensurability on thermal transport at the Si / Si interface

[0068] The silicon / silicon heat transfer system was experimented. At the beginning of operation, the heat transfer system reached the relaxation temperature and maintained a constant temperature under the action of the thermostat.

[0069] The mismatch angle is set to 0~45°, and the temperatures of the heat source and cold source are set to 320K and 280K respectively. The interface thermal conductivities under different mismatch angles are compared to determine the dependence of the interface thermal conductivities on the mismatch angle.

[0070] The heat transfer model in this invention is used to explore the interface heat transfer mechanism under commensurate and incommensurate conditions. In each time step of the heat transfer process, a constant amount of heat is added to the heat source and removed from the cold source. The Berendsen thermostat controls the temperature of the heat source and the cold source at the target value, thereby establishing a temperature gradient in the direction of heat conduction. Therefore, the heat flow J It can be expressed as ,in: Q Indicates the amount of heat added to a heat source or absorbed from a cold source; A is the interface contact area; t Indicates the total time of each simulation.

[0071] Interfacial thermal conductivity (ITC) is an important factor in accurately predicting the interface temperature rise, which is the ratio of the interface heat flux to the interface temperature difference. The interface thermal conductivity is expressed as ,in: G for ITC; is the interface temperature difference, and the interface temperature distribution is collected using the linear fitting method.

[0072] Figure 3 a shows the dependence of the interfacial thermal conductivity on the mismatch angle. The results show that ITC gradually decreases with the increase of the mismatch angle. At the micro-nano scale, the boundary effect caused by size also affects the interfacial heat transport. Figure 3b shows the interface thermal conductance of the hot area and the cold area at different sizes. As the system size increases, the interface thermal conductance gradually increases. The reason why the system size leads to enhanced ITC is that the increase in size leads to a reduction in the boundary scattering effect, thereby enhancing ITC.

[0073] The increased normal load will reduce the interlayer distance and the ITC will reach about 320MW / m 2 K. Therefore, in order to ensure the consistent impact of boundary effects on ITC under different contact states and considering the limitation of computational resources, a heat transfer model with 15 × 15 × 15 UCs in the hot and cold regions is selected under any mismatch angle.

[0074] Figure 4 a and 4b respectively show the calculation process of extracting the interface temperature difference using SW potential and Tersoff potential, and the temperature at the center of the interface, i.e., the hot area, is calculated using the linear fitting method. T A and cold areas T B , so the interface temperature difference .

[0075] (3) Determine the effects of interfacial interlayer distance, Lennard-Jones (LJ) potential, force constant, and phonon state density on interfacial thermal conductivity

[0076] In order to further reveal the intrinsic mechanism of the influence of interface commensurability on interface thermal conductivity, the present invention extracted the interlayer distance, Lennard-Jones (LJ) potential energy, force constant and phonon state density, and determined the dependence of interface thermal conductivity on interface commensurability.

[0077] Extract the interlayer distance under different mismatch angles, such as Figure 5 (a). As the mismatch angle increases, the interlayer distance gradually increases and maintains the minimum distance under the commensurate state. In order to further explore the intrinsic reasons for the enhancement of interfacial thermal conductivity under commensurate contact, the interfacial Lennard-Jones potential energy and force constant under different mismatch angles were calculated, as shown in Figure 2. Figure 5 (b) and 5(c). The LJ potential energy is expressed as: ,in: , , and They represent the interlayer distance, potential well depth and equilibrium separation constant respectively. The LJ potential energy and force constant both decrease as the mismatch angle increases and maintain their maximum values ​​under the common degree state. This is because the reduced interlayer distance increases the potential energy interaction on the contact surface, thereby increasing the force constant and further improving the interface heat transfer efficiency.

[0078] In addition, under commensurate contact, the lattice structure of the interface atoms is completely symmetrical. Once the contact surface undergoes interlayer rotation, that is, the interface contact state changes, the lattice structure of the atoms at the interface will mismatch, which will cause changes in the interface potential energy, force constant, and heat transport. Therefore, in the commensurate-incommensurate transition, the force constant and interface potential energy gradually decrease, resulting in a decrease in ITC under the incommensurate state. The force constant of the interlayer interaction is expressed based on the second-order derivative of the LJ potential as: .

[0079] Since energy is carried by phonons, in order to further reveal the intrinsic mechanism of phonon heat transport under commensurate and incommensurate states, the present invention extracts the phonon density of states (PDOS) of the contact surface to monitor the contribution of phonons to heat transport. Figure 6 The PDOS curves under different contact states are shown in Figure 2. Compared with the commensurate state, the PDOS under incommensurate contact moves toward the low-frequency mode, which leads to the red shift of the phonon spectrum. In fact, the reduction of the force constant weakens the interlayer interaction, thereby reducing the phonon transmittance, inhibiting the excitation of high-frequency phonons, and thus enhancing the interface thermal conductivity.

[0080] Therefore, the present invention can effectively control the interface heat transport characteristics by adjusting the mismatch angle between the silicon layers.

[0081] (4) Determine the effect of normal load on heat transport at Si / Si interface

[0082] In order to reveal the correlation between the interface thermal conductivity and the normal load, the present invention further determines the dependence of the interface thermal conductivity on the normal load during the heat transfer process by calculating and analyzing the interface thermal conductivity under different normal loads.

[0083] Extract interface temperature difference and heat flow under commensurate and incommensurate conditions, such as Figure 7 (a) and 7(b). Regardless of whether it is in the commensurate or non-commensurate state, the interface temperature difference decreases with the increase of the normal load, and the interface temperature difference under commensurate contact will be smaller than that under non-commensurate state. At the same time, the heat flux under commensurate contact is larger and gradually increases with the increase of the normal load. Figure 7 (c) shows that the normal load will significantly enhance the interfacial thermal conductivity at the Si / Si interface, and the interfacial thermal conductivity is stronger under the commensurate contact state.

[0084] (5) Determine the effect of normal load on interfacial interlayer distance, Lennard-Jones (LJ) potential energy and force constant

[0085] In order to further explore the intrinsic reason why the normal load enhances the interfacial thermal conductivity, the interlayer distance, interface LJ potential energy and force constant were calculated and analyzed to determine the influence of the normal load on the interface interlayer distance, LJ potential energy and force constant.

[0086] Depend on Figure 8 (a) It can be found that as the normal load increases, the interlayer distance gradually decreases; the interlayer distance under non-commensurate contact is greater than the interlayer distance under commensurate contact. Figure 8 (b) and 8(c) show that the reduced interlayer distance enhances the LJ interface potential and increases the force constant, which is particularly evident in the commensurate state.

[0087] In fact, without the application of normal load, the heat transfer system is in the lowest energy configuration, i.e., the LJ potential energy valley; once the normal load is applied, the system will be dragged away from the potential energy valley. Therefore, as the normal load increases, the interlayer distance decreases, and the interlayer potential energy and force constant between the hot and cold regions increase, thereby enhancing the heat transfer capacity at the interface. Therefore, the present invention shows that the normal load will significantly enhance the heat transfer capacity of the silicon / silicon interface.

[0088] (6) Determine the effect of mismatch angle and normal load on heat

[0089] In order to further explore the relationship between interface thermal conductivity and heat, the present invention determines the contribution of mismatch angle and normal load to heat in the heat transfer process by analyzing the total heat absorbed by the cold source under different contact states and normal loads.

[0090] Fig. 9 (a) shows that as the interlayer mismatch angle increases, the total heat absorbed by the cold source gradually decreases. In the common state, the heat is at the highest position, which means that the greater the interface thermal conductivity, the more heat will be transported by the heat transfer interface.

[0091] Fig. 9 In (b), the normal load will increase the total heat of the system, and the total heat in the commensurate state is greater than that in the non-commensurate state. The reason is that the interface thermal conductivity generated under non-commensurate contact is weak, which reduces the heat transfer efficiency at the interface, resulting in less heat transfer.

[0092] In summary, the present invention provides an important basis for understanding the internal mechanism of heat transfer in solid materials with different contact interfaces and for finding effective methods to control interface thermal conductivity by studying the energy and heat transport at the silicon / silicon interface based on interface commensurability and normal load.

[0093] The technical solution provided by the present invention is described in detail above. The principle and implementation mode of the present invention are described in detail using specific embodiments herein, and the explanation of the above embodiments is only used to help to deeply understand the method and core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for controlling interface thermal conductivity based on coupling of interface commensurability and normal load, comprising the following steps: (1) Establish a molecular dynamics heat transfer model consisting of a hot area and a cold area of ​​silicon / silicon, directly change the mismatch state of the interface by rotating the hot area, and apply a spring in the z direction of the hot area to apply a normal load to the heat transfer system; The heat region comprises a heat transfer atomic region I, a heat source and a rigid body layer; each atom in the heat region is provided with a spring in the x, y and z directions; and periodic boundary conditions are provided in the x and y directions; The cold region includes a fixed wall, a cold source and a heat transfer atomic zone II; A heat transfer interface is formed between the heat transfer atomic region I and the heat transfer atomic region II; ⑵Execute simulation and process data: ① Taking the mismatch angle as 0~45°, the heat source and cold source temperatures are set to 320K and 280K respectively, and comparing the interface thermal conductance under different mismatch angles to determine the dependence of the interface thermal conductance on the mismatch angle; ② Taking the mismatch angle as 0~45°, the heat source and cold source temperatures are set to 320K and 280K respectively, and comparing the interfacial distance, Lennard-Jones potential energy and force constant under different mismatch angles to reveal the intrinsic reason why the interface commensurability affects the interface thermal conductivity; ③ Taking the mismatch angle as 0° and 45°, compare the phonon state density under commensurate and incommensurate states to determine the effect of state density on heat transport at interfaces with different commensurate properties; ④ Taking the normal load as 0~50nN, the heat source and cold source temperatures are set to 320K and 280K respectively, the interface temperature difference, heat flow and interface thermal conductivity under different normal loads and interface commensurability are calculated, and then the relationship between the change curve of interface thermal conductivity and normal load under different commensurability is obtained; ⑤ Taking the normal load as 0~50nN, the heat source and cold source temperatures are set to 320K and 280K respectively, and calculating the interfacial distance, Lennard-Jones potential energy and force constant under different normal loads and interface commensurability to reveal the intrinsic mechanism of the normal load affecting the interfacial thermal conductivity; ⑥ Take the mismatch angle as 0~45° and the normal load as 0~30nN, calculate the total heat absorbed by the cold source during the heat transfer process, and determine the influence of interface thermal conductivity coupled with different interface commensurability and normal load on the heat.

2. The method for controlling interface thermal conductivity based on coupling of interface commensurability and normal load according to claim 1, characterized in that: In the step (1), the temperature of the heat source is 320K and the temperature of the cold source is 280K.

3. The method for controlling interface thermal conductivity based on coupling of interface commensurability and normal load according to claim 1, characterized in that: The simulation and data processing in step (2) also include: taking the mismatch angle as 0° and 45°, the normal load as 15 nN, comparing the phonon state density under the commensurate and non-commensurate states, and determining the intrinsic mechanism of the influence of the state density on the thermal transport of interfaces with different commensurate properties.

4. The method for controlling interface thermal conductivity based on coupling of interface commensurability and normal load according to claim 1, characterized in that: The simulation and data processing in step (2) also includes: taking the normal load as 0~50nN, setting the heat source and cold source temperatures to 320K and 280K respectively, calculating the interface temperature difference, heat flow and interface thermal conductivity under different normal loads and interface commensurability, and then obtaining the change curve relationship between the interface thermal conductivity and the normal load under different commensurability, and determining the influence of the normal load on the interface thermal conductivity.

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