Nanoscale friction reduction and fatigue monitoring due to ultrasonic excitation

DLC film interfacial fatigue and changes in friction coefficient phenomena were investigated during quasi-static nanoindentation/scratch while the sample surface was excited ultrasonically. An original experimental setup combines nanoindenter, SPM scanner and ultrasonic transducer operating in an elastic standing wave mode. Nanoindentation loading–unloading curves revealed delamination induced excursions after a certain number of ultrasonic loading cycles. Drastic changes in quasi-statically monitored friction coefficient during nanoscratch were correlated with sample vibration amplitude and loading force. Resulting indentation/scratch film delamination effects and surface wear patterns were examined by an in situ SPM technique. Ultrasonically excited nanoindentation and nanoscratch techniques can be considered as fast and qualitative methods to characterize critical tribo surfaces for data storage devices.