Development of a continuous microscratch technique in an atomic force microscope and its application to study scratch resistance of ultrathin hard amorphous carbon coatings

A method to measure friction during scratching at linearly increasing loads in a commercial atomic force/friction force microscope (AFM/FFM) has been developed. The normal load was increased in small increments over the required range for the scratch using a software module while the friction signal was measured via a breakout box and data acquisition computer. Topography images of the scratch were obtained in situ with the AFM in tapping mode with minimal loss of damage event information. This technique was employed to study the scratch resistance of hard amorphous carbon coatings of thicknesses ranging from 20 nm down to 3.5 nm deposited by different commercially available deposition techniques on a silicon substrate.