EFFECT OF FRICTION ON ATOMIC-FORCE MICROSCOPY OF ION-IMPLANTED HIGHLY ORIENTED PYROLYTIC-GRAPHITE

An atomic force microscope investigation of the surface of highly oriented pyrolytic graphite (HOPG) after implantation with 165 keV C+ ions established the presence of a dendritic ridge structure. Examples were found for which the image contrast of the ridge structure reversed when scanned in the backward direction. This result is demonstrated to be due to variations in the surface friction. The surface of the ridge structure was found to be characterized by a coefficient of friction that was approximately one-half that on the remainder of the surface. Smaller attractive forces between the scanning tip and the surface were also observed on the ridges as well. In favorable cases, it is apparent that consideration of mechanical effects in atomic force microscopy can provide qualitative surface information in addition to the topographical images. A comparison is made with unimplanted HOPG, and some instrumental methods for enhancing or reducing the effect of friction are discussed.