Atomic and Electronic Structure of Ultra-Thin Metal Epitaxy on Metal and Semiconductor Surfaces.
Date of Award
Doctor of Philosophy (PhD)
Physics and Astronomy
The fundamental study of heteroepitaxy has proved to have profound influences on technological applications of thin films, particularly due to the reduced dimensionality and quantum mechanical effects found in these unique nanostructured systems. In this study, particular attention is given to the correlations between atomic-scale morphology and the consequential electronic structure of heteroepitaxial systems that exhibit deviations from traditional growth modes in the initial stages of growth. Surface-confined systems are especially interesting because they exhibit properties that are fundamentally different from the bulk and often have no bulk analogs existing in nature. The surface-sensitive techniques of variable-temperature scanning tunneling microscopy and synchrotron-based angle-resolved photoelectron spectroscopy have been used to investigate the atomic and electronic structures of Ag/Cu(110), Ag/Ni(110), Ni/Ag(100) and Be/Si(111)-(7 x 7). Particular attention is given to the initial stages of growth (submonolayer coverages), where each metal on metal system exhibits a bulk-immiscible, surface-confined alloy formation and Be/Si(111) undergoes reactive epitaxy. The metal on metal systems studied in this work exhibit a trend in sp-d electronic hybridization due to the negligible d-band overlap between the adatoms and the substrate and their increased coordination through surface alloy formation (Ag/Cu(110) and Ag/Ni(110)) and subsurface clustered growth (Ni/Ag(100)). As a result, each system displays quasi-three-dimensional electronic structures. Beryllium deposition on the (7 x 7) reconstructed surface of Si(111) results in an amorphous clustered silicide compound at temperatures as low as 120 K. High temperature annealing of the Be/Si(111) surface results in a universal ring cluster structure commonly seen in epitaxial transition metal silicide surfaces. Because it has been previously determined that ring clusters occur only for systems with a metal-silicon bond length less than 2.5 A, it is thus concluded that the Be-Si bond length is less than 2.5 A, a value consistent with theoretical predictions.
Hite, Dustin Alexander, "Atomic and Electronic Structure of Ultra-Thin Metal Epitaxy on Metal and Semiconductor Surfaces." (2001). LSU Historical Dissertations and Theses. 344.