ATOMIC SPECIES IDENTIFICATION IN SCANNING-TUNNELING-MICROSCOPY BY TIME-OF-FLIGHT SPECTROSCOPY

We report the first chemical identification of a cluster of atoms from identifiable sites on an extended crystal surface. The instrument use d combines the functions of a scanning tunneling microscope (STM) with a time-of-flight (TOF) atom probe. Atoms are transferred from regions of interest identified in STM images to the tip, from which they are ejected into a TOF spectrometer. Preliminary results are shown in whic h a cluster of silicon atoms taken from the Si(111) 7 x 7 surface is i dentified by TOF spectra. Applications of these ''atomic tweezers'' fo r microanalysis are discussed. (C) 1996 American Vacuum Society.