Etching, Roughening, and Patterning of Silicon(100) With Halogens
Xu, Guangjun
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https://hdl.handle.net/2142/87873
Description
Title
Etching, Roughening, and Patterning of Silicon(100) With Halogens
Author(s)
Xu, Guangjun
Issue Date
2005
Doctoral Committee Chair(s)
Weaver, John H.
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
With variable temperature STM, the surface modification dynamics of Cl- and Br-Si(100)-(2 x 1) were studied. Chlorine (Bromine) caused surface roughening that created pits and regrowth islands with minimal desorption of SiCl 2 (SiBr2). The roughening and equilibrium morphologies at 700--750 K for surfaces with various coverages of Cl were studied. The morphologies of regrowth islands and pits at equilibrium state provide a model system to study the 2-D feature shape, which is a result of the interplay involving step free energies, surface stress, and adsorbate interactions. I-destabilization of Si(100)(2 x 1) at near saturation at 600 K created vacancy line defects that were perpendicular to substrate dimer row direction, distinctive from those induced by Cl and Br under similar conditions since the latter formed atom and dimer vacancy lines that were parallel to the dimer rows. Using first-principles density functional theory, we determined the steric repulsive interactions associated with iodine and showed how the observed defect patterns were related to these interactions. Concentration dependent studies showed that the vacancy patterns were sensitive to the I concentration. Dimer and atom vacancy lines were favored at lower coverage. Chemisorption configurations and diffusion of halogen species on Si(100)-(2 x 1) were investigated. Of the Cl, Br, and I group, Cl has the highest single atom diffusion barrier and I has the lowest. The role of C-type defects, dissociated H2O, was recognized. The consequences of Si adatom deposition on Br-saturated Si(100)-(2 x 1) have also been studied. Br changes the diffusion, nucleation, and growth of Si on Si(100).
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