Study On The Influence Of Surface Topography On The Mechanical And Electrical Properties Of Silicon Nanostructures

Silicon is the foundation of today's semiconductor industry and an important material for manufacturing single crystal silicon electronic devices.Low-dimensional silicon nanomaterials can be well integrated with traditional silicon production processes.Therefore,studying the mechanical and electrical properties of silicon nanomaterials has become an important topic in the application of semiconductor electronic components.It is inevitable that the surface is oxidized during the processing of silicon materials.As the structure of silicon materials enters the nanometer size,the influence of surface oxides on its physical properties becomes more and more important.This paper mainly adopts the method of simulation calculation to systematically study the influence of surface oxide size on the vibration frequency of silicon nanobeams and the influence of different elements saturated silicon nanobeams on its electronic structure.The work of the thesis is divided into the following two parts:(1)The molecular dynamics simulation method is used to study the influence of the thickness and size of the oxide layer on the vibration frequency of the silicon nanobeam when the upper and lower surfaces of the silicon nanobeam are oxidized.The results show that the vibration frequency of pure silicon nanobeams and silicon nanobeams with oxide layers decreases as the length increases.The increase of the cross-sectional area increases the vibration frequency of the nanobeam,but the effect is not significant.In addition,the vibration frequency of silicon nanobeams with an oxide layer is greater than that of pure silicon nanobeams,and as the thickness of the oxide layer increases,the vibration frequency increases.(2)The first principles are used to study the influence of the upper and lower surfaces of the three different elements of H,O and F saturated silicon nanobeams on its energy band structure,density of states and differential charge density.The results show that the band structures of pure silicon nanobeams and most of the saturated silicon nanobeams are metallic,and only the saturated silicon nanobeams of a certain thickness exhibit indirect band gap semiconductivity.The density of states has some distorted small peaks in both the valence band and the conduction band.As the thickness increases,these distorted small peaks gradually decrease,and the density of states energy continues to increase.The areas of electron accumulation and electron loss are concentrated at the interface between saturated atoms and Si atoms.