Scanning tunneling microscopy of semiconductor surfaces J.A. Kubby Xerox Wilson Center for Research and Technology, Xerox Corporation, M/S W-114-41D, 800 Phillips Road, Webster, N Y14580, USA and J.J. Boland Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA ELSEVIER Amsterdam-Lausanne-New York-Oxford-Shannon-Tokyo