Test and analysis on nanohardness using an AFM-based system

A system based on atomic force microscope(AFM) and a (Berkovich) diamond tip was developed for nanohardness and elastic modulus measurements.This system can directly gain the load-displacement curves that couldn't be obtained from indent software of AFM itself.The diamond tip was controlled by sending signal to achieve loading and unloading and gathering the real-time data.In this way the load-displacement curve and data could be acquired directly. Single point experiments were conducted on single-crystal copper and single-crystal aluminum thin films.TriboIndenter produced by Hysitron Inc was used to do the validated experiments.The results show that the system is suited for nanohardness measurement of the softer materials.By analysis on the effects of substrate material on nanohardness and elastic modulus,it can be known that the substrate has great influence on the mechanical characteristic of the film when the thickness of film is less than 5 to 10 times the peak depth.Nanohardness increases with a decrease in the indentation depth,which indicates a strong size effect,but there is no significant effect on the elastic modulus based the load-displacement curves.