BULK DEFECTS IN GRAPHITE OBSERVED WITH A SCANNING TUNNELING MICROSCOPE

Scanning tunnelling microscopy (STM) has been used to observe a misori entation of a graphite layer that is buried several layers below the s urface. A nanoscale periodic pattern superimposed on the atomic graphi te lattice has been observed. The appearance of the superperiodic feat ures in the STM image is shown to be clearly tip-sample distance depen dent. We suggest that a subsurface misorientation, several layers deep , causes a nanoscale moire pattern, which can propagate to the surface and contributes to the STM image. This result is rather surprising as STM is thought to be unable to image bulk defects. (C) 1998 Elsevier Science B.V. All rights reserved.