Date of Award
Doctor of Philosophy
Physics and Astronomy
Michael C. Tringides
Fundamental electrical conductance measurement has been studied in-situ in two dimensions in the Ag/Si(111) system as a function of the incident adatom flux rate with a four probe technique. A conductance study in a three dimensional conical structure was also carried out with field emission techniques. Field emission is now well established and has been used in this case to characterize a novel geometry for use in flat panel displays to replace cathode ray tube monitors. For the two dimensional study on Ag/Si(111), the origin of conduction is still unclear, as both transport by means of percolating Ag clusters and conduction through the substrate via electrons transferred from the film have both been suggested as the conduction mechanism. We have carried out experiments by varying the flux rate to decide between these two possible mechanisms. Smoother films are expected at lower growth rates which would result in faster drops in the four probe voltage. However, the four probe voltage vs. deposition time for various flux rates collapse into a universal curve which indicates that the morphology is not relevant and supports conduction through the substrate. In the conductance measurements in the three dimensional system, a single, lateral micromachined W protrusion on a silica substrate is examined to identify the factors controlling emission in micromachined structures. The I-V characteristics and emission pattern indicate that miniprotrusions of a few hundred Angstroms, much smaller than the nominal radius of the tip, exist on the tip and are responsible for the emission. Adsorption-desorption events from the background environment are the cause of large fluctuations in the emitting current. Comparison of the emission of a single tip to gated arrays suggest that only a fraction of the tips in the array are emitting.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Kevin R. Kimberlin
Kimberlin, Kevin R., "Sub-micron scale conduction processes on clean surfaces " (1994). Retrospective Theses and Dissertations. 11278.