Adhesion Induced Mechanochemical Wear Of Monocrystalline Silicon And Its Micro Protection Research

With the rapid development of micro processing and detection technology,nanotechnology has gradually transferred from laboratory to practical field,including almost all fields of modern technology.Since the 21^st century,the development of nanotechnology has provided unlimited potential for the further development of high tech manufacturing industries such as electronic communication,semiconductor processing,artificial intelligence,etc.As a representative of nanotechnology,micro electro mechanical system(MEMS)has shown great potential in many fields such as human daily life,social production and national defense security.However,due to the surface and size effects,nano tribological problems such as adhesion and wear have become the key factors that restrict the long-term stable and reliable service of MEMS devices.In this paper,the adhesion induced mechanochemical wear of monocrystalline silicon is studied by an environmental controlled atomic force microscope.Furthermore,the protective ability and the initial damage rule of DLC film to nano wear of monocrystalline silicon are studied,and the nano tribological properties of DLC film are improved by surface modification.In the end,the microscopic protective properties of graphite are studied,and the mechanism of ultra-low friction between interfaces based on graphite is revealed,which provided theoretical guidance for the selection of friction pairs of MEMS devices and the design of lubricants.During the research process,in order to reveal the micro wear mechanism of the surface of monocrystalline silicon and other materials,X ray photoelectron spectroscopy is used to detect the evolution of surface groups in the experiment process,Raman spectroscopy was used to study the structural evolution of DLC films,and high-resolution transmission electron microscopy is used to characterize the atomic structure of the removal area.The main conclusions are as follows:(1)The mechanochemical wear behavior of monocrystalline silicon surface is studied,and the law and mechanism of adhesion induced wear are revealed.It is found that the mechanochemical reaction on the surface of monocrystalline silicon results in the wear of monocrystalline silicon under low contact stress,and the adhesion induced wear on the silicon surface under atmospheric environment proves the existence of Si-O-Si bond between interfaces directly.(2)Study on the micro protective properties and running-in mechanism of DLC film.By comparing the micro wear behavior of DLC film and monocrystalline silicon,it is found that DLC film can effectively inhibit the nano wear of monocrystalline silicon,and the formation of the transfer layer and the removal of the oxide layer on the surface of DLC film lead to the sharp decrease of the friction and wear rate of DLC film in the micro running in stage.(3)Surface modification of DLC film for low friction.The surface treatment of DLC films by HF acid pickling,annealing and UV irradiation is attempted in order to improve the micro tribological properties of DLC films by removing the oxide layer,increasing the graphitization degree of DLC films and realizing the easy transfer of DLC films.(4)Study on the micro protective properties and low friction mechanism of graphite.It is found that graphite can greatly reduce friction while achieving low wear.Further research shows that the weak charge transfer between interfaces is the key to achieve ultra-low friction.This discovery will contribute to the selection of low friction pairs and the design of lubricants.In this paper,the nano tribology problems are studied which restrict the long-term stable and reliable service of MEMS devices.The adhesion induced mechanochemical wear of monocrystalline silicon are systematically studied,in which the damage mechanism of monocrystalline silicon at nano scale is revealed.Moreover,the micro protective properties of DLC film and graphite are discussed,which are the MEMS oriented protective materials.This research is enriching mechanization,meanwhile,providing the theoretical basis and scientific guidance for improving the reliability and prolonging the service life of MEMS.