A Study of Highly Oriented Pyrolytic Graphite and Gold by Scanning Tunneling Microscopy

Date of Graduation

Summer 2006

Degree

Master of Science in Materials Science

Department

Physics, Astronomy, and Materials Science

Committee Chair

Shyang Hwang

Abstract

Scanning Tunneling Microscopy (STM) is an efficient technique which allows imaging solid surfaces with unprecedented resolution. STM is based on scanning a metallic tip just about the sample surface while monitoring the tunneling current between the metallic tip and the conducting surface which are in very close proximity but not actually in physical contact. During the scan, the probe sensor samples a specific signal which is interpreted in terms of structure, electronic or force interaction information from the interface. The tips used were made from an alloy of platinum and iridium by mechanically cutting them. The purpose of our experiments was to image the surfaces of Highly Oriented Pyrolytic Graphite (HOPG) and gold surfaces at the atomic level. HOPG is one form of graphite which has highly orientated surface with respect to the layer-stacking direction. An atomically flat and clean surface can be easily obtained by peeling off the surface layer with a scotch tape. The (111) surface of gold is a versatile surface for preparation and observation of molecular and nano structures. To obtain atomically flat surfaces, the gold samples were first annealed under hydrogen flame. We obtained atomic resolution of both HOPG and gold surfaces. The image quality of the STM micrographs depends on the properties of the tip and the control parameters of the feedback system.

Keywords

scanning tunneling microscopy, highly oriented pyrolytic graphite, gold, platinum/iridium tips, tunneling current

Subject Categories

Materials Science and Engineering

Copyright

© Praneeth Kumar Ramasagaram

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Dissertation/Thesis

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