A Morphological Study of Highly Oriented Pyrolytic Graphite at Atomic Level Using 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) has been applied extensively to study the composition and distribution of molecules or nanostructures assembled on a surface. In this technique, a sophisticated electronic feedback system is combined with a piezoelectrically mounted, conductive tip to probe the sample surface. The STM tips were made of platinum/ iridium wire using a mechanical cutting procedure towards a rank of atomic sharpness, while the surface of highly oriented pyrolytic graphite was prepared by cleaving. Image quality of STM micrographs depends greatly on the properties of the tip and the control parameters of the feedback system. By applying a gape voltage of 10̃200 mV and a feedback current of 5̃50 nA, we have achieved atomic resolution at room temperature under ambient conditions. The symmetry of graphite unit cells is clearly resolved under STM. Atomic force microscopy (AFM) images of the same samples are presented for comparison, as will scanning electron microscopy (SEM) images of atomically sharp tips used in the STM experiments.

Keywords

scanning tunneling microscopy, introduction to STM, STM of HOPG, surface characterization by STM, modes of operation in STM

Subject Categories

Materials Science and Engineering

Copyright

© Rakesh N.T.V. Janardhan

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Dissertation/Thesis

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