High temperature nanomechanical and nanotribological behavior of sub-5 nm nitrogen-doped carbon overcoat films

摘要

Elevated temperature tribological properties of ultra-thin nitrogen-doped carbon overcoat (NCOC) protective film for magnetic disks were investigated. NCOC with three different thicknesses (2.5, 3.5, and 4.5 nm) were examined in terms of both chemical and mechanical properties at temperatures up to 300 degrees C. The chemical changes were traced by XPS, revealing that the configuration of both carbon and nitrogen elements change partially from sp(3)- to sp(2)-hybridizations with exposure of NCOC samples to annealing. The friction coefficient, wear rate, and deformation of the NCOC films were measured using nanoscratch/wear experiments. Three sets of mechanical experiments verified the operating temperature and thickness dependence of the tribological behavior of the NCOC films. The NCOC samples show that the average wear depth is acceptably small after exposure to annealing, thus offering durable films for high temperature applications. Noteworthy, the permanent reduction in mechanical properties associated with annealing reduces in the presence of N dopants.