Doctoral Dissertations

Andrew G. Wig

Date of Award

8-2000

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Thomas L. Ferrell

Committee Members

Robert Compton, Marianne Breinig, Thomas Callcott

Abstract

Absorption spectroscopy is demonstrated to be feasible using a photon scanning tunneling microscope (PSTM) combined with a spectroscope. Methods of improving the spatial resolution and spectroscopic capabilities are studied in order to determine their potential practicability. Analysis of the photon scanning tunneling microscope(PSTM) and modifications made to the microscope are included with experimental results demonstrating certain image and spectral resolution capabilities. Results Showing both the PSTM absorption spectra of gold island films and their independently acquired PSTM images are presented. An alternative scanning probe method involving photons is additionally examined. The new method is demonstrated to require specific improvements in order that it might provide a distinct improvement in resolution. The new type of scanning probe microscope is one utilizing nonlinear photonics: the nonlinear scanning tunneling microscope (NSTM). Basic results are described and two-photon fluorescence measurements are presented to demonstrate the principle of operation. In any scanned probe microscope or spectroscope,resolution is strongly dependent upon the characteristics of the signal as a function of distance to the sample and knowledge of these characteristics. The NSTM functionality is most dependent upon the sample-probe gap, but the gap also determines resolution in the PSTM. Hence measurements and calculations showing an analysis of the characteristics of the separation between the probe and sample surface are also presented.

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