Imaging graphite in air by scanning tunneling microscopy: Role of the tip
We have been successful in obtaining atomically resolved images of highly oriented pyrolytic graphite (HOPG) in air at point contact. Direct contact between tip and sample or contact through a contamination layer provides a conduction mechanism in addition to the exponential tunneling mechanism responsible for scanning tunneling microscopy (STM) imaging. Current–voltage (I–V) spectra were obtained while scanning in the current imaging mode with the feedback circuit interrupted in order to study the graphite imaging mechanism. Multiple tunneling tips are probably responsible for images without the expected hexagonal or trigonal symmetry. Our observations indicate that the use of HOPG for testing and calibration of STM instrumentation may be misleading.
Additional Information© 1988 American Vacuum Society. Received 24 July 1987; accepted 13 October 1987. We gratefully acknowledge the technical assistance of Carol Garland of the California Institute of Technology Material Research Group and J. Wandass and R. Jones of the NRL Surface Chemistry Branch. This material is based upon work supported by a National Science Foundation Graduate Fellowship and by the office of Naval Research Grant No. N00014-86-K-0214, the Shell Companies Foundation, Inc., and the National Institute of Health Grant No. R01 GM 37226-01. One of us (W.J.K.) wishes to acknowledge the support of SDIO/Innovative Science and Technology Office through an agreement with NASA.
Published - COLjvsta88.pdf