Nanotribology of Si oxide layers on Si by atomic force microscopy

Atomic force microscopy (AFM) has been used for tribological studies of Si surfaces covered by oxide layers of various kinds: chemical oxides prepared by the SCI (NH4OH/H2O2/H2O) and the SC2 (HCl/H2O2/H2O) treatments and a thermal oxide. In the case of the SCI chemical oxide, the oxide layer was scratched and the underlying Si substrate was ploughed by the Si3N4 AFM tip. On the other hand, no wear of the sample was noted on the other surfaces: the AFM often produced elevated patterns in the shape of the scanned areal which were no longer visible after HF etching. By annealing the SCl-treated surface in N-2 gas at above 200 degreesC for 30 min. the oxide layer could not be scratched any more. By soaking the thermal oxide in KOH, the oxide layer was then scratched. It is concluded that the presence of OH bases is the necessary condition for the nano-scratching of the oxide layers. (C) 2001 Elsevier Science B.V. All rights reserved.