UC San Diego

Two different areas of surface science topics have been studied using a synergistic combination of experiment and theory, which provides for both explanation and clarification of experimental results, as well as prediction for future experiments. Low coverage oxidation Ge(100) was studied using scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and DFT modeling of bonding and electronic structures. 100 L O₂ exposure was found to pin the Fermi level near the valence band due to a strong coverage effect, with theoretical findings consistent with experimental observations. The passivation of Ge(100) surface using molecular silicon monoxide (SiO) was studied using STM, STS, and DFT modeling of bonding and electronic structures. The adsorbed SiO was found to form trimer, (SiO)₃, trough- bridging pyramids that did not pin the Fermi level. Ordered molecular metal oxide (ZrO₂ and HfO₂) adsorbate interfaces on Ge(100) were studied using DFT modeling of bonding and electronic structures. Metal-down and oxygen- down structures were found to be energetically degenerate, with metal-down structures forming metallic interface and oxygen-down structures forming passive interfaces. Calculated density of states minima shifts were attributed to possible band bending extending beyond the depth of the computational Ge slabs. The gas-surface dynamics and etching by low-coverage Cl₂ on Al(111) was studied using time-of-flight mass spectrometry, King-and-Wells sticking measurements, and density functional theory (DFT) modeling. Hyperthermal desorption of AlCl&l₃ was documented and attributed to fast-time-scale surface diffusion and agglomeration of adsorbed Cl to form aluminum chlorides with activated chemisorption states having potential energies above the vacuum level