Anisotropy in wear processes measured by scanning probe microscopy

Wear of smooth amorphous carbon overcoats was performed in continuous slidi ng contact in the range of 10(4)-10(7) cycles by a diamond or diamond-like carbon counterbody. The overcoats on superpolished hard disks were examined using friction and topographic scanning probe microscopy. An optimal Fouri er (Wiener) filter was designed which preferentially filtered noise out of images of the smooth films. Second derivatives of the z-height were calcula ted parallel and perpendicular to the wear direction. The crosscorrelation of a friction force image and the corresponding z-height image shows that t he correlation length is also extended in the wear direction. The local fri ction is independent of the z-height before wear. but increases with z-heig ht upon wear. A model for the z-height and friction force evolution in cont act sliding is discussed and compared with data. (C) 1998 Elsevier Science S.A. all rights reserved.