考慮晶格缺陷的單晶4H-碳化硅納米劃擦過程分子動力學仿真研究

中圖分類號：TG580 文獻標志碼：A

Abstract：The mechanismof nano-grinding of single crystal silicon carbide（SiC）with lattice defects remains unclear.A molecular dynamics simulation system is used to study the nano-scratching mechanism of single crystal SiC with latice defects.The simulation model including diamond abrasive grains and 4H-SiC workpieces with different latice defects is built.The molecular dynamics simulation results reveal the effectsof different defect types on key parameters such as interatomic potential energy，，temperature，stress and machining performance.It is found thatvacancydefects lead to instabilityinthe interatomicpotentialenergyof the workpiece，which inturn results in increasing the temperatureof the workpiece up to 671 K after scribing，while dislocation defects show relative stability.During nano-scratching，crystals with dislocation defects exhibit the highest average paradigm equivalent stress of 5.29GPa，while crystals with vacancy defects exhibit the lowest stressof 5.O7GPa，which suggests hat vacancy defectsreduce the yield strengthandfavour theremoval of atoms，whereas dislocation defects increase the yield strength and impede the removal of atoms.Furthermore，vacancy defects inhibited dislocation nucleation and reduced the thickness of thedamagelayer，whereas dislocation defects led to significant dislocation formation and a deeper damage layer.

Key Words：silicon carbide ;lattice defects ;molecular dynamics ;nano-scratching;surface damage

碳化硅（SiC）以其優異的物理和化學性能代替了傳統半導體材料，成為在高溫、高壓、大功率和耐輻射等特殊環境下工作的半導體器件的理想選擇.SiC有多種晶型，其中4H-SiC在光電器件、高溫電子器件等方面有著廣泛的應用.然而，4H-SiC具有超高的斷裂韌性和硬度，屬于難加工的硬脆性材料.而且在單晶4H-SiC的外延生長過程中，可能引入不同類型的晶格缺陷，這些晶格缺陷可能會影響加工，最終影響器件的性能1.為了探討具有晶格缺陷的單晶碳化硅的超精密加工性能，對單晶碳化硅材料去除機制進行深人的分子級理解至關重要.

分子動力學（moleculardynamics，MD）是一種有效地模擬原子運動及原子之間相互作用的方法.MD模擬在研究超精密拋光和切割機理方面發揮了重要作用，該方法基于原子水平模擬單個磨粒的納米劃痕，直觀、準確地獲得材料在塑性變形過程中原子尺度結構演化行為[2-7.目前，許多學者已經應用分子動力學模擬方法來研究單晶碳化硅在精密加工過程中的力學性能和去除機理.Schuh等8研究了4H-SiC的壓痕，并提出了在基于成核的統計框架內分析初期塑性的方法，該方法能夠預測在壓痕過程中最可能出現的機制事件.Tian等在4H-SiC和6H-SiC材料的C面和Si面進行的一系列劃擦試驗，研究了材料的去除和相關的亞表面缺陷.Meng等[\"通過MD模擬研究了應變速率和磨損熱對單晶3C-SiC去除行為的影響，發現磨損溫度導致SiC表面熱軟化，從而降低屈服應……