Study On Machining Technology In AFM Tapping Mode

The nano-processing technology based on the atomic force microscope(AFM)has the advantages of simple processing steps,diversified processing materials,and can realize in-situ imaging characterization of nano-scale patterning,and is widely used as a new nano processing method for research.However,the processing mechanism based on the AFM tapping mode is not clear,and the process of the nano-structure with controllable depth cannot be realized,and the process parameters need to be groped.Therefore,in the light of the above-mentioned problems,this paper has carried out the experimental research on the processing technology under the tapping mode,the main work includes:Firstly,the forming process of machining grooves in tapping mode is studied,and the continuous machining process of high frequency vibration probe is discretized.The nano indentation method is adopted,and the single point constant depth multiple indentation test is carried out.The relationship between indentation depth and indentation times is studied,and it is concluded that the indentation depth increases gradually with the increase of indentation times.By comparing the change of surface properties between machined surface and non-machined surface,and the relationship between the surface property of machined surface and the number of hits,the deformation law of the material in the process is obtained,and the forming process of grooves in the tapping mode is clarified,and the relationship between the surface properties of the machined surface and the number of hits is obtained.That is,the plastic deformation occurs on the surface of the sample after the first indentation,with the number of hits.With the increase of the elastic recovery region,the deformation of the elastic recovery region can not be restored,and the depth of the grooves increases gradually.Secondly,nano-grooves were fabricated on PMMA(polymethyl methacrylate)under AFM tapping mode.The effects of machining direction,machining speed and Z-direction displacement on the morphology of machined grooves were studied.It is concluded that the depth of grooves is most affected by the machining speed.The machining of nano-groove with controllable depth is realized by controlling the machining speed in a certain range.The machining depth model is established and verified.Finally,the machining of simple three-dimensional structure nano-square pit in AFM tapping mode is realized,and the influence of machining direction,machining speed,feed and Z displacement on the surface quality of the bottom of square pit structure is studied.It is concluded that the influence of the feed is the greatest;Orthogonal test method was used to determine the significance of each process parameter and the optimal combination of process parameters by using the method of extreme difference and variance analysis.The empirical model of bottom roughness and machining parameters of square pit was obtained by using MATLAB programming software to regress the results of orthogonal test by three-dimensional quadratic polynomial regression,and the experimental results were verified by experiments.