Experimental Study On Wear Of Single Crystal Silicon Tip Of Atomic Force Microscope

Atomic Force Microscope has become an essential tool in the field of nanoscienceincluding surface science, materials science, surface chemistry, electrochemistry,biology, metrology, etc. The heart of an AFM is a sharp tip that interacts with thesurface of a sample at a force on atomic level. With this interaction, variation of surfaceheight at nano-scale is measured. Due to that, the tip may be worn during scanning. Thewear of tip will not only degrade the measurement resolution, but also bring some errorsto the experimental results. Therefore, minimizing the tip wear loss in work andstudying the method of tip wear qualification and influence of tip wear on measurementbecome more significant. This thesis will study and analyze the issues that caused by tipwear.First, the method that can qualify the tip wear has been researched. A tip is used toscan the specific geometry structure—nano-grating. And the relationship between thevariation of the tip radius and the spectrum of scan simulation is analyzed utilizing theFourier transform method. Then, the quantitative evaluation of the tip radius has beenachieved. Meanwhile, using the power spectral density the isotropic random surface isstudied, and qualitatively evaluation of the tip wear in the measurement process ispresented.Second, in the tapping mode how to optimize the scanning parameter that canreduce the tip wear has been investigated. Effects of the engaging rate, the amplitudesetpoint, the scan rate and the feedback gain on the tip wear is analyzed respectively indetail. Combining with the simulation of vibrating probe, the optimal parameters thatcan reduce the tip wear under the premise of well scan are obtainedFinally, influences of tip wear on the measurement of ultra-precision machiningsurface are studied through experiments. Different wear degree tips are chosen tomeasure morphology of the ultra-precision machining surface respectively. And thecorresponding measuring results are analyzed by the method of surface roughnessanalysis and power spectral density. Thus, the effect of tip wear on the surfacemeasurement results is obtained.