A research method for regulating phonon transport at structural lubrication interfaces

Abstract

This invention relates to a research method for regulating phonon transport at structural lubrication interfaces. Using silicon / silicon as the research object, a molecular dynamics model is established. By comparing the changes in frictional force under different mismatch angles and loads at the interface, the influence on the frictional force of the silicon / silicon system is determined, and its underlying mechanism is revealed. This invention also calculates and analyzes probe temperature, interface temperature difference, and friction interface thermal resistance, determining the relationship between interface thermal resistance and frictional force under different mismatch angles and loads; calculates and analyzes the phonon density of states distribution under different mismatch angles and loads, determining the dependence of the density of states on interface thermal resistance during friction; and calculates and analyzes the number of phonons excited by the substrate under different mismatch angles and loads, determining the dependence of the phonon number on frictional energy dissipation, etc. This invention provides an effective method for clarifying the influence of different mismatch angles and normal loads on the frictional force between silicon / silicon interfaces, thus providing theoretical guidance for regulating the frictional and heat transfer behavior between semiconductor silicon layers.

Description

Technical Field

[0001] This invention relates to the field of molecular dynamics, and in particular to a research method for regulating phonon transport at structural lubrication interfaces. Background Technology

[0002] In mechanical engineering, electronic chips, military equipment manufacturing, and other fields, friction typically occurs between two contacting sliding surfaces. Wear and damage caused by friction are major causes of shortened lifespan of mechanical components and equipment failures, resulting in significant economic losses. Macroscopic friction is the sum of atomic or nano-friction effects; therefore, exploring the mechanism of nano-friction and striving to achieve ultra-low friction is of great significance for reducing energy loss and extending the lifespan of mechanical equipment. Furthermore, the rapid development of digitalization and high integration of electronic components promotes rapid heat accumulation on sliding surfaces, which greatly affects product stability and lifespan. Therefore, there is an urgent need for high thermal conductivity materials and effective research methods to regulate energy transfer at the contact interface.

[0003] Scholars have conducted in-depth research and summaries on methods for reducing friction. Since 1990, research teams have theoretically combined molecular dynamics (MD), first-principles calculations, and finite element analysis to conduct extensive research on friction. Meanwhile, other researchers have used atomic microscopy (AFM), scanning electron microscopy (SEM), and scanning tunneling microscopy (STM) to detect friction, thereby achieving superlubricity. For example, when hexagonal graphene slides on square bilayer graphene, the lattice mismatch at the graphene / graphene interface is caused by a change in the sliding direction, resulting in ultra-low friction. Dienwiebel et al. also confirmed that the friction between the contact interface is related to the rotation angle by measuring the friction between tungsten and graphene surfaces. Their results indicate that superlubricating properties are observed at the friction interface under incommensurable contact conditions.

[0004] In essence, nanofriction is an energy dissipation process generated by lattice vibrations. Localized high temperatures form during sliding at solid / solid interfaces, accumulating energy as phonons and ultimately causing severe damage to mechanical devices. Adjusting phonon transfer at the friction interface is highly beneficial for optimizing the performance of mechanical components. Torres et al. proposed that phonon friction is related to the contact state of the interface, with phonon friction in commensurate states being significantly greater than in incommensurate states. Kajita et al. demonstrated through AFM experiments that changes in the internal properties of the solid affect phonon energy dissipation, thus influencing the friction evolution process. Recently, Mello et al. proved that changes in frictional force are affected by the phonon distribution during energy dissipation. Furthermore, Wei et al. proposed that when the sliding speed exceeds a critical value, the phonons excited during friction cannot dissipate rapidly, leading to a decrease in frictional force. These studies have demonstrated that frictional energy dissipation can be modulated through phonon properties. However, the internal mechanisms of phonon excitation and transport during friction under different contact states remain unclear and require further clarification.

[0005] Silicon is the most dominant semiconductor material to date and has broad research prospects, playing a crucial role in communications, semiconductors, and aerospace. This invention reveals the phonon transport in silicon / silicon interface structural lubrication by altering the contact state. First, a silicon / silicon friction system is established and its relevant components are introduced. Then, by combining probe temperature, interface temperature difference, and friction interface thermal resistance, the frictional energy dissipation laws under commensurate and incommensurate conditions are revealed. Finally, the excitation and transport processes of phonons on the structural lubrication interface are quantitatively studied, and the phonon origins that produce completely different frictions under commensurate and incommensurate conditions are decoded. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a research method for regulating phonon transport at the structural lubrication interface. Taking silicon / silicon as the research object, this invention provides an effective research method to clarify the influence of different mismatch angles and normal loads on the frictional force between silicon / silicon interfaces, and thus provides a theoretical basis for realizing the regulation of phonon transport at the structural lubrication interface.

[0007] To address the above problems, this invention provides a research method for regulating phonon transport at structural lubrication interfaces, the method comprising:

[0008] A molecular dynamics model was established: the entire model includes a silicon probe and a silicon substrate. The probe consists of a rigid layer and a free-moving layer, while the substrate consists of a right-end fixed layer, a temperature-controlled layer, and a free-moving layer. A friction interface is formed between the two free-moving silicon atomic layers. Each atom of the probe is equipped with a spring in the X, Y, and Z directions. The spring in the X direction drives the probe to slide at a constant speed of 10 m / s. The spring in the Y direction is used to adjust the rotation angle of the probe relative to the substrate, which is the mismatch angle. The spring in the Z direction is used to apply a normal load. Periodic boundary conditions are set in the X and Y directions, and free boundary conditions are set in the Z direction.

[0009] Simulations were performed and data processed: The mismatch angle range was taken as -20° to 110°. Frictional force and thermal resistance at the silicon / silicon interface were calculated under normal loads of 60 nN and 100 nN, respectively, to obtain the relationship between frictional force and thermal resistance at different mismatch angles. With normal loads ranging from 60 to 200 nN, the frictional force, probe temperature, and interface temperature difference under different contact states and normal loads were calculated. Combined with the thermal resistance at the interface, the influence of interface thermal resistance on interface temperature difference and frictional force was determined. The density of states distribution under different mismatch angles and normal loads was compared, and the number of excited phonons at the interface substrate was considered to determine the influence of density of states and phonon number on frictional force at the silicon / silicon interface under different mismatch angles and normal loads. This provides a theoretical basis for controlling phonon transport at the structure-lubricated interface.

[0010] Preferably, the process of performing the simulation and processing the data further includes:

[0011] The barrier height was calculated at 0K and 300K under different mismatch angles, normal loads, and temperatures. The analysis of the barrier height under different conditions was used to determine the dependence of the barrier height on the silicon / silicon interface friction force during the friction process.

[0012] Preferably, the process of performing the simulation and processing the data further includes:

[0013] Calculate the friction force, probe temperature, interface temperature difference and friction interface thermal resistance under different normal loads with loads ranging from 60 to 200 nN. Also, calculate the interface thermal resistance of silicon / silicon friction systems with normal loads of 60 nN and 100 nN with mismatch angles ranging from -20 to 110° and temperature of 0 K.

[0014] By comparing the frictional force, probe temperature, interface temperature difference, and frictional interface thermal resistance under different mismatch angles and normal loads, the influence of frictional interface thermal resistance on the temperature difference and frictional force of the silicon / silicon interface under different mismatch angles and normal loads can be determined.

[0015] Preferably, the method further includes: using eight atoms from selected regions to calculate the density of states of the silicon / silicon interface probe and the substrate; analyzing the density of states results under different mismatch angles and normal loads to determine the relationship between the thermal resistance of the friction interface and the density of states under commensurability / incommensurability and different normal loads.

[0016] Preferably, the method further includes: using eight atoms from selected regions to calculate the number of phonons excited by the substrate at the silicon / silicon interface, analyzing the phonon number distribution under different mismatch angles and normal loads, and quantitatively determining the relationship between the number of phonons generated under commensurability / incommensurability and the amount of frictional energy dissipation.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. In this invention, a molecular dynamics model is first established, and then the model is run under different mismatch angles and normal loads to calculate and analyze the interfacial friction force during the friction process. The influence of different mismatch angles and normal loads on the friction force between silicon / silicon interfaces is determined: under commensurability (i.e., mismatch angles of 0° or 90°), the friction force between the sliding interfaces reaches its maximum; while under incommensurability, the friction force is almost zero, and the interfacial friction force increases with the increase of the normal load. This invention provides an effective research method for clarifying the influence of different mismatch angles and normal loads on the friction force of silicon / silicon interfaces, and thus provides a theoretical basis for realizing the control of phonon transport at the structure-lubricated interface.

[0019] 2. The present invention further determines the relationship between the barrier height and the friction force during the friction process by calculating and analyzing the barrier height under different mismatch angles, normal loads and temperatures.

[0020] 3. The present invention further determines the influence of interface thermal resistance on friction force under different mismatch angles and normal loads by calculating and analyzing the change of friction interface thermal resistance with mismatch angle: the greater friction force between friction interfaces is attributed to the lower friction interface thermal resistance.

[0021] 4. To investigate the relationship between the density of states and the thermal resistance of the friction interface during the friction process, this invention further analyzed the phonon density of states distribution under different mismatch angles and normal loads, determined the influence of the phonon density of states on the thermal resistance of the friction interface under different mismatch angles, and further determined that: more effective energy dissipation channels appear under the commensurate state, which causes the energy generated by friction to be efficiently transferred from the probe to the substrate. Therefore, the thermal resistance of the friction interface is reduced, resulting in greater energy dissipation.

[0022] 5. The present invention further calculates and analyzes the phonon number distribution excited by the substrate under different mismatch angles, and determines the dependence of the interfacial friction force on the phonon number under different mismatch angles.

[0023] In summary, the present invention, based on the study of energy dissipation by phonon transport at the friction interface, can provide theoretical guidance for regulating the friction and heat transfer behavior of silicon nanodevices. Attached Figure Description

[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0025] Figure 1 The molecular dynamics model provided for the embodiments of the present invention.

[0026] Figure 2 The dependence of the silicon / silicon interface friction force on the mismatch angle under different normal loads and temperatures is provided for embodiments of the present invention.

[0027] Figure 3 The relationship between barrier height and mismatch angle, temperature and normal load is provided for embodiments of the present invention.

[0028] Figure 4 The influence of normal load on interfacial friction force is provided in the embodiments of the present invention.

[0029] Figure 5 The probe temperature provided in this embodiment of the invention is used as a function of the normal load.

[0030] Figure 6 The relationship between interface temperature difference and normal load is provided for embodiments of the present invention.

[0031] Figure 7 The friction interface thermal resistance provided in this embodiment of the invention is used as a function of the normal load.

[0032] Figure 8 The functional relationship between the thermal resistance of the friction interface and the mismatch angle and normal load is provided in the embodiments of the present invention.

[0033] Figure 9 The period length in the sliding direction of the probe and substrate provided in the embodiments of the present invention.

[0034] Figure 10 The density of states of a commensurate / incommensurate probe and substrate under a normal load of 60 nN is provided in this embodiment of the invention.

[0035] Figure 11 The density of states of commensurate / incommensurate probes and substrates under a normal load of 100nN provided in this embodiment of the invention.

[0036] Figure 12 The number of phonons excited by the substrate under a normal load of 60 nN provided in this embodiment of the invention is commensurate / incommensurate.

[0037] Figure 13The number of phonons excited by the substrate under a normal load of 100nN provided in this embodiment of the invention is commensurate / incommensurate. Detailed Implementation

[0038] This invention focuses on silicon / silicon friction systems and explores a research method for phonon excitation and transport at the structural lubrication interface under the coupling of mismatch angle and normal load. The invention provides a method for controlling phonon transport at the structural lubrication interface, specifically including the following:

[0039] (1) Establishing a molecular dynamics model

[0040] refer to Figure 1 The model in this invention includes a probe and a substrate. Both the probe and substrate comprise 15×15×15 UCs, with each UC containing 8 silicon atoms. The atoms on the far left of the probe, with a thickness of 7 UCs, are set as rigid bodies (RT), and these rigid atoms have no thermal vibrations but can move relative to the substrate. Simultaneously, the atoms on the far right of the substrate, with a thickness of 4 UCs, are a fixed layer confined to their initial positions, and all six degrees of freedom of all atoms are restricted to prevent movement in any direction. Adjacent to the fixed layer, with a thickness of 3 UCs, is a temperature-regulating layer, where the Berendsen method is used to regulate the system temperature; the remaining layers are subject to Newtonian mechanics.

[0041] To eliminate boundary effects at the microscopic level, periodic boundary conditions are applied in the X and Y directions to maintain the dynamic equilibrium between the probe and the substrate by simulating an infinite planar dimension, while a free boundary condition is set in the Z direction. Because the initial model dimensions of the probe and substrate in the friction system are the same, and combined with the periodic boundary conditions, the friction interface remains in dynamic thermal equilibrium during the frictional sliding process. Each atom of the probe is equipped with a spring with a stiffness of 4800 N / m in the X, Y, and Z directions: the rigid body layer of the probe is connected to the support (e.g., ...) via springs. Figure 1 (b) In the silicon / silicon triboelectric system, the probe (RT) slides at a constant speed of 10 m / s via a spring in the X direction, and the frictional force can be calculated based on the spring force. Different normal loads are applied in the Z direction via the spring. Simultaneously, to prevent the probe from rotating around the Z-axis and translating along the Y direction during sliding, a spring is also applied in the Y direction of the RT. A temperature-regulating layer maintains the system temperature at 0 K or 300 K. Subsequently, to better observe the phonons excited on the triboelectric interface, the time step is set to 0.5 fs, thus capturing the vibrational information of all atoms on the triboelectric interface. The angle at which the probe rotates around the Z-axis relative to the substrate from the perfectly matched lattice direction is defined as the mismatch angle. This invention changes the mismatch angle by rotating the probe to create different contact states at the triboelectric interface. In this invention, the mismatch angle ranges from -20° to 110°. Throughout the MD simulation, the applied normal load F... nWhen applied to a rigid layer, once the silicon / silicon interface contacts at a certain mismatch angle and reaches a stable state, the probe slides on the substrate at a constant speed in the X direction.

[0042] In this invention, the interaction between the probe and the substrate can be described by the Lennard-Jones (LJ) potential, and the covalent bond interaction between any two silicon atoms in the probe and the substrate can be described by the Stillinger-Weber (SW) potential. The LJ potential strength between the probe and the substrate remains constant and is unaffected by the sliding speed.

[0043] In this invention, eight atoms are selected on the interface layer where the probe and the substrate are in contact to calculate the phonon density of states and the number of phonons in the silicon / silicon triboelectric system, thereby studying the relevant properties of excited phonons.

[0044] (2) Determine the influence and mechanism of mismatch angle and normal load on silicon / silicon interface friction.

[0045] Experiments were conducted on the aforementioned silicon / silicon friction system. At the beginning of operation, the friction model system reached the relaxation temperature and maintained a constant temperature under the action of the temperature-regulating layer.

[0046] (2.1) Effect of mismatch angle and normal load on silicon / silicon interface friction force

[0047] Using mismatch angles ranging from -20° to 110°, the frictional force of the silicon / silicon system under different mismatch angles and normal loads of 60nN and 100nN was calculated. The influence of different mismatch angles and normal loads on the frictional force of the silicon / silicon interface was determined by comparing the frictional forces.

[0048] In the tribological system established in this invention, we study the frictional behavior between the probe and the substrate under different states. The instantaneous spring force during the sliding process can be regarded as the instantaneous frictional force. The average frictional force (i.e., the frictional force in this invention) can be obtained by averaging the instantaneous frictional forces.

[0049] Figure 2In (a) and (b), the frictional forces at temperatures of 0 K and 300 K under normal loads of 100 nN and 60 nN, respectively, as a function of the mismatch angle ranging from -20° to 110°, were calculated. The results show that the frictional force varies periodically with the mismatch angle at 90°, independent of temperature and normal load. The 90° symmetry of the frictional force is consistent with the periodicity of the silicon crystal structure. When the friction interface rotates from 0° to 90°, it returns to the commensurable state. Then, the frictional force between the probe and the substrate reaches its maximum value under the commensurable state, while the frictional force is quite low under the incommensurable state. Furthermore, the frictional force decreases sharply during the transition from commensurable to incommensurable, and the friction curve exhibits a relatively wide transition range. In commensurable contact sliding, the frictional force at 300 K is lower than that at 0 K, perfectly reflecting the thermal lubrication phenomenon. The friction curves also show that the interfacial frictional force increases with increasing normal load, which is attributed to the deeper inter-atoms on the contact surface, requiring greater lateral force.

[0050] at last, Figure 2 It was also demonstrated that the trend of frictional force change is independent of temperature, with temperature only playing a role in thermal lubrication. To eliminate the influence of ambient temperature phonons, this invention only extracts phonon information generated solely by friction at the sliding interface, and subsequently only calculates relevant data at 0K.

[0051] (2.2) Mechanism of the influence of mismatch angle and normal load on silicon / silicon interface friction force

[0052] Friction is the force that opposes the relative motion of two contacting sliding surfaces. Due to the applied spring force and the change in mismatch angle, the friction interface transitions from commensurate to incommensurate, causing atoms at the interface to deviate from their equilibrium positions, resulting in atomic lattice mismatch. Therefore, the friction force is minimal in the incommensurate state. In the commensurate state, the atomic lattices of the friction interface are perfectly matched and have the same vibrational characteristics. More work is required to cause dislocations at atomic positions, so the interface friction force reaches its maximum. Furthermore, the interface friction force increases with the increase of the normal load. This is because with a larger load, the atoms at the interface are more deeply embedded, reducing the interatomic distance and making the crystal structure more compact. Restoring it to its original state requires overcoming a greater force. To further explore the intrinsic mechanism of friction, this invention incorporates the potential barrier height for explanation.

[0053] (3) Determine the relationship between the barrier height and the silicon / silicon interface friction during the friction process.

[0054] To investigate the effect of barrier height on friction, this invention further calculated the barrier height under different contact states, normal loads, and temperatures. Through analysis of the barrier height under different conditions, the relationship between barrier height and friction during the friction process was determined.

[0055] In this invention, Figure 3(a) shows that the energy barrier at a mismatch angle of 0° is much larger than that at other mismatch angles, meaning that more energy needs to be dissipated to cross the higher energy barrier in the former case. The barrier height decreases as the mismatch angle increases. The incommensurability shows a lower energy barrier, resulting in less energy dissipation.

[0056] This invention demonstrates that increasing the temperature can lower the corresponding energy barrier, and the greater the load, the greater the energy barrier.

[0057] (4) Determine the dependence of interfacial thermal resistance on silicon / silicon interfacial friction during the friction process.

[0058] This invention also analyzes the thermal resistance of the friction interface under different mismatch angles and normal loads in silicon / silicon systems, and determines the relationship between the thermal resistance of the friction interface and the friction force of the silicon / silicon interface under different mismatch angles and normal loads. The details are as follows.

[0059] Using a mismatch angle of -20° to 110° and a temperature of 0 K, the thermal resistance of the triboelectric interface of the silicon / silicon system was calculated under normal loads of 60 nN and 100 nN, respectively. Furthermore, the frictional force, probe temperature, interface temperature difference, and thermal resistance of the triboelectric interface were calculated under loads of 60 to 200 nN. The results were compared to determine the influence of the thermal resistance of the triboelectric interface on the frictional force of the silicon / silicon system interface under different mismatch angles and normal loads. The results show that: Figure 4 This indicates that the frictional force under commensurate conditions increases linearly with increasing normal load, and this linear relationship eliminates the adhesion effect at the contact interface. The frictional force under commensurate conditions is always greater than that under incommensurate conditions. Since friction is an energy dissipation process, this means that more mechanical energy is converted into heat and dissipated at the commensurate contact interface. It is expected that higher friction will result in higher interface temperatures, therefore the probe temperature under commensurate conditions should be higher. However, this is not the case. Figure 5 The results showed that, under incommensurability, the probe temperature was much higher than under commensurability. To explain this unexpected phenomenon, the present invention further calculated the interface temperature difference, such as... Figure 6 As shown, the interface temperature difference is large under incommensurability. This invention assumes that this significant difference is due to the different interfacial thermal resistance (ITR) under different contact states between the interfaces. A larger ITR can effectively prevent frictional energy from being transferred from the probe to the substrate, thus leading to a larger interface temperature difference and a higher probe temperature. The IRT calculation process is as follows:

[0060] In this invention, frictional sliding between surfaces will excite a large number of phonons, causing mechanical energy to be converted into heat. Ultimately, the heat is absorbed by the temperature-regulating layer. Therefore, the rate of frictional energy dissipation is equal to the rate at which the temperature-regulating layer absorbs heat, which can be represented by the heat flow J. Where J and Q represent the rate (or heat flow) at which the thermostat extracts heat and the frictional energy, respectively. When heat flows through the interface, it typically manifests as a sudden drop in the interfacial temperature difference. Assuming a uniform heat distribution between the contact surfaces, the heat passing through the frictional interface is equal to half of the total heat absorbed by the thermostat. According to Fourier's law, the ITR at the frictional interface can be expressed as: Where R is ITR, A is the contact area of ​​the friction interface, and ΔT is the interface temperature difference.

[0061] Based on the above ITR formula, this invention calculates the commensurability / incommensurability ITR under different mismatch angles and normal loads. Figure 7 The results show that the ITR under incommensurability is several orders of magnitude higher than that under commensurability, and decreases significantly with increasing normal load. (Reference) Figure 8 The change in mismatch angle alters the atomic lattice matching degree between interfaces. This invention calculated the ITR (internal temperature range) for mismatch angles ranging from -20° to 110° under different normal loads. The results show that the ITR reaches its lowest point during the transition from incommensurability to commensurability, and decreases with increasing normal load. The period of ITR variation within the mismatch angle range is 90°, which is consistent with... Figure 2 The periodic variation trends of frictional force under different mismatch angles are similar. Furthermore, it is demonstrated that under incommensurability, a larger ITR hinders energy transfer between the probe and the substrate; therefore, ultra-low friction corresponds to a higher ITR. These findings provide a theoretical basis and guidance for phonon transport excited at frictional interfaces.

[0062] (5) Determine the effect of phonon state density on the thermal resistance of the friction interface during the friction process.

[0063] To further explain the significant difference in ITR between commensurate and incommensurate friction interfaces, this invention extracts the phonon density of states between the probe and the substrate during friction. The phonon excitation at the interface and the fabrication of the phonon transport mechanism are further explained. By obtaining the phonon density of states under different states and normal loads, and combining this with the changes in frictional force and friction interface thermal resistance, the influence of the phonon density of states on the friction interface thermal resistance during friction is determined.

[0064] This invention first reveals the period of the probe's sliding distance in different directions. Figure 9 This diagram illustrates a 2×2×1 UCs. Under commensurability, the sliding period lengths of both the probe and the substrate along the X-direction are "a" (where a is the lattice constant of silicon). Under incommensurability, i.e., when the mismatch angle is 45°, the sliding period length of the substrate becomes... Meanwhile, the probe sliding period length caused by the substrate along the sliding direction remains "a". The vibrational frequencies of atoms on the contact surface generated by periodic excitation are concentrated on the rubbing board frequency and harmonics, and the rubbing board frequency f0 is: L is the length of the sliding period, v sLet be the sliding speed. Therefore, the washboard frequencies under commensurate and incommensurate conditions are respectively... and

[0065] The calculation process of phonon density of states between the system friction interfaces: In the MD simulation, the velocity autocorrelation function VAF can be calculated as follows: Where M is the number of atoms in the selected region, <> is the time averaging operator, Δt is the time step, td is the delay time, and N is the time interval. cor v represents the autocorrelation velocity quantity. j,i This is the thermal velocity of atom j corresponding to a sliding time of i. The phonon density of states is calculated from the VAF using a fast Fourier transform: ω is the angular frequency, and τ is the total sliding time.

[0066] In this invention, Figure 10 and Figure 11 The figures represent the phonon density of states at 60 nN and 100 nN under commensurability and incommensurability, respectively. The dashed lines represent the rubbing frequency and harmonics. This invention shows that the density of states of the probe and substrate are discrete, and the acoustic modes excited at the interface are uniformly distributed at the rubbing frequency. However, under incommensurability, the frequencies between the probe and substrate are not equal, and the above results are independent of the normal load. Under commensurability, the energy generated by friction can be effectively transferred from the probe to the substrate and is eventually absorbed by the thermostat. However, under incommensurability, the energy dissipation channels at the friction interface, i.e., the different vibration frequencies between the probe and substrate, lead to a mismatch, resulting in the failure of energy transfer between the probe and substrate. The blockage of the energy transfer channels between the contact surfaces increases the thermal resistance of the friction interface, causing... Figure 5 The probe temperature increased. The results show that the higher the matching degree of energy dissipation channels between the probe and the substrate, the stronger the energy transfer efficiency at the friction interface, leading to lower friction interface thermal resistance and greater frictional force. These conclusions reveal the relationship between phonon density of states and friction interface thermal resistance, providing further explanation and guidance for excited phonon transport at the structure-lubricated friction interface.

[0067] (6) Determine the relationship between phonon number and silicon / silicon interface friction during the friction process.

[0068] This invention combines the number of excited phonons at the silicon / silicon interface to characterize the amount of frictional energy dissipation, and determines the influence of the number of phonons on the frictional force under different mismatch angles and normal loads.

[0069] Friction is an energy dissipation process involving the excitation and conversion of phonons between sliding surfaces. The amount of frictional energy dissipation is measured by the number of excited phonons. This invention analyzes the number of excited phonons on a substrate, exploring the energy aspect. Figure 2 The evolution of frictional force.

[0070] In this invention, Figure 12 and13 The values ​​represent the number of phonons excited by the substrate under commensurate and incommensurate conditions, with normal loads of 60 nN and 100 nN, and sliding speeds of 20 m / s and 10 m / s, respectively. The results show that phonons excited at the friction interface are still generated at the washboard frequency and harmonics, and the frequency range of excited phonons changes significantly under different contact conditions. Under commensurate conditions, phonons can still be excited at the 8th harmonic of the washboard frequency, while under incommensurate conditions, it is difficult to identify other phonons after the 2nd harmonic of the washboard frequency. Notably, by calculating the total energy generated during friction, the results show that the energy dissipated under commensurate conditions is 5-7 times that under incommensurate conditions. Therefore, this invention demonstrates that the total number of phonons excited during friction is higher under commensurate conditions across the entire frequency range, resulting in greater frictional force.

[0071] The technical solution provided by this invention has been described in detail above. Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The explanations of these embodiments are merely for the purpose of helping to deepen the understanding of the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A research method for regulating phonon transport at structural lubrication interfaces, characterized in that, The research methods include: A molecular dynamics model was established: the entire model includes a silicon probe and a silicon substrate. The probe includes a rigid layer and a free-moving layer, and the substrate includes a right-end fixed layer, a temperature-controlled layer, and a free-moving layer. A friction interface is formed between the free-moving layer of the probe and the free-moving layer of the substrate. Each atom of the probe is provided with a spring in the X, Y, and Z directions. The spring in the X direction will drive the probe to slide at a constant speed of 10 m / s. The spring in the Y direction is used to adjust the rotation angle of the probe relative to the substrate, which is the mismatch angle. The spring in the Z direction is used to apply a normal load. Periodic boundary conditions are set in the X and Y directions, and free boundary conditions are set in the Z direction. Simulations were performed and data processed: The mismatch angle range was set to -20° to 110°. Frictional force and thermal resistance at the silicon / silicon interface were calculated under normal loads of 60nN and 100nN, respectively, to obtain the relationship between frictional force and thermal resistance at different mismatch angles. With normal loads ranging from 60 to 200nN, the frictional force, probe temperature, and interface temperature difference under different contact states and normal loads were calculated. Combined with the thermal resistance at the interface, the influence of interface thermal resistance on interface temperature difference and frictional force was determined. The density of states distribution under different mismatch angles and normal loads was compared, and the number of excited phonons at the interface substrate was considered to determine the influence of density of states and phonon number on frictional force at the silicon / silicon interface under different mismatch angles and normal loads. This provides a theoretical basis for controlling phonon transport at the structure-lubricated interface.

2. The research method as described in claim 1, characterized in that, The process of performing the simulation and processing the data also includes: The barrier height was calculated at 0K and 300K under different mismatch angles, normal loads, and temperatures. The analysis of the barrier height under different conditions was used to determine the dependence of the barrier height on the silicon / silicon interface friction force during the friction process.

3. The research method as described in claim 1, characterized in that, The process of performing the simulation and processing the data also includes: Calculate the friction force, probe temperature, interface temperature difference and friction interface thermal resistance under different normal loads with loads ranging from 60 to 200 nN. Also, calculate the interface thermal resistance of silicon / silicon friction systems with normal loads of 60 nN and 100 nN with mismatch angles ranging from -20 to 110° and temperature of 0 K. By comparing the frictional force, probe temperature, interface temperature difference, and frictional interface thermal resistance under different mismatch angles and normal loads, the influence of frictional interface thermal resistance on the temperature difference and frictional force of the silicon / silicon interface under different mismatch angles and normal loads can be determined.

4. The research method as described in claim 1, characterized in that, Also includes: The density of states of the silicon / silicon interface probe and the substrate were calculated using eight atoms from selected regions respectively. The density of states results under different mismatch angles and normal loads were analyzed to determine the relationship between the thermal resistance of the friction interface and the density of states under commensurability / incommensurability and different normal loads.

5. The research method as described in claim 1, characterized in that, Also includes: The number of phonons excited by the substrate at the silicon / silicon interface was calculated using eight atoms from selected regions. The phonon number distribution under different mismatch angles and normal loads was analyzed to quantitatively determine the relationship between the number of phonons generated under commensurate / incommensurate conditions and the amount of frictional energy dissipation.

Images