The Calibration Of The Shape Of Atomic Force Microscope Tips

The atomic force microscope(AFM)is increasingly employed in nanotechnology.AFM could acquire the 3D topography images of the samples with atomic resolution and also the force-distance curves of the materials.Force-distance curve is a fundamental tool in surface science,biology and many other fields of research.AFM tip shapes play a major role in the measurement.For example,the very sharp features will be dilated during scanning due to AFM tip radius.In the indentation measurement,the deformation behaviors of the materials are strongly related with AFM tip shapes.In this paper,the blind tip reconstruction(BTR)and nanoindentation methods were both employed to calibrate the AFM tip.BTR is a feasible algorithm to characterize the tip.However it is sensitive to noise and the noise threshold could affect the estimated results particularly.The calibration of the probe profile by nanoindentation methods involves the determination of area functions and the selection of elastic contact models.The main work of the paper includes the calibration of the tip by BTR method,nanoindentation method and the correction method of the indentation morphology.The selection of the optimal noise threshold in BTR method has been verified by stimulation.Besides,the area data extraction of the 3D models has been done and the area function of the AFM tip was determined.Then two types of AFM tips were calibrated by nanoindentation method.The calibrated AFM tips were triangular pyramid probes with 40 nm nominal tip radius and 8 nm nominal tip radius.After the calibration of the tip radius,a method to correct the indentation morphology was applied in the nanoindentation measurement.It was verified by the results of the hardness measurement in nanoindentation.