Experimental Study On Brittle Material Nanometric Cutting With FIB Bombardment Assisted Under SEM Online Observation

With the rapid development of manufacturing industry,micro-nano processing technology has been developed and applied widely.Because the surface and subsurface damage caused by nanocutting will impact the mechanical performance and working life of the workpiece,it is necessary for us to enhance the machined surface integrity and have a good knowledge to the nanocutting machining mechanism and the processing technology optimization method.This dissertation reviewed the research status of nanocutting,and performed the diamond nanocutting of the typical brittle material?i.e.single crystal silicon and silicon carbide?on the online nanometric cutting device based on scanning electron microscope?SEM?,which was designed and established by our research group,and we also research the nanometric cutting of focused ion beam?FIB?Ga ion implanted brittle material optimization method.This dissertation mainly finishes the following aspects of work:?1?In order to accurately analyze and quantitatively characterize the damage characteristics of the monocrystalline silicon caused by FIB bombardment,the Monte Carlo simulation of Ga ion implantation of monocrystalline silicon was performed,and the simulation and analysis of the Ga ion bombard typical brittle materials monocrystalline silicon and germanium was realized using the software of the SRIM.The controllable experimental of Ga ion implantation of monocrystalline silicon was also carried out.At the same time,the method and technology of the transmission electron microscope?TEM?sample preparation by FIB were studied,and the TEM sample preparation and the revalent characterization analysis was realized.?2?The nanometric cutting of ion implanted monocrystalline silicon was performed with the help of the online nanometric cutting device based on SEM.The different phenomenon of the nanocutting between the modificated monocrystalline silicon by Ga ion bombarded(FIB gallium ion energy of 30 keV,implantation dose of5×10¹⁶ ions/cm²)and the monocrystalline silicon was analyzed from the perspective of the machined surface quality,the brittle-ductile transition depth and so on.The study reveal that when the cutting depth was the same,the modified crystal silicon can realize the ductile-regime removing of the substrate material,and the machined surfaced was smooth,while the monocrystalline silicon without ion modification will be brittle machining,and the machined surface behaved brittle pitting.?3?In order to investigate the influence of the sub-surface damage on the quality of subsequent processing,the multiple cutting experiment was performed with the help of the online nanometric cutting device based on SEM.The multiple nanocutting tests of monocrystalline silicon were performed using a diamond tool,and the radium cutting edge is 75nm.The study reveals that when the total cutting depth less than the depth of brittle-ductile transition,the brittle removal phenomenon?i.e.micro-cracks pitting,etc.?was observed periodically.In addition,the cracks pitting can be repaired when the cutting depth is small.?4?The online nanometric cutting experiment based on SEM of the ion implanted silicon carbide was performed.The silicon carbide was modified by ion beam implantation,then the single and multiple diamond nanocutting experiments were carried out on the surface of the modified/unmodified silicon carbide.The study reveals that the ion implantation enhance the depth of the brittle-ductile transitionand and the machined surface quality.