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|Title:||Studies of the growth of silicon and germanium overlayers: Surface, interface, and thin film formation|
|Doctoral Committee Chair(s):||Chiang, Tai-Chang|
|Department / Program:||Physics|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Physics, Condensed Matter
Engineering, Materials Science
|Abstract:||Surface reconstruction, atomic charge transfer, step formation, atomic structure and defects on the clean Si and Ge surfaces and the grown Si-on-Ge and Ge-on-Si overlayers were systematically studied. Adsorption mechanisms, surface species, chemical reactions, atomic composition and ordering, and film morphology during the growth using molecular beam epitaxy (MBE) and vapor phase epitaxy (VPE) were thoroughly investigated. In these studies, detailed atomistic descriptions of crystal growth by MBE and VPE were obtained by utilizing high resolution core-level photoemission with synchrotron radiation, electron diffraction, and scanning tunneling microscopy.
The dimer bond ionicities of Si and Ge(100)-(2 x 1) surfaces were examined by means of epitaxial growth of Ge on Si(100)-(2 x 1). The MBE growth technique allows replacing the top Si layers layerwise by Ge. After substituting Ge for the top Si dimer layer, we can obtain the core-level line shape for the Ge dimer layer without the interference from bulk Ge emission and the core-level line shape for Si emission without the top dimer layer contribution. The results clarify the charge asymmetry of the two dimer atoms. Subsurface core-level shifts were also identified.
The growth of Si on Ge(100)-(2 x 1) and Ge(111)-c(2 x 8) via MBE was explored with high resolution core-level spectroscopy and STM. By monitoring the distinct surface core-level shifts and intensities, the atomic species and their relative populations were revealed. The film morphology, growth mode, and the surface structure of the clean surfaces and the grown film were all investigated by STM. The results showed significant intermixing at the interface at fairly low temperature. The atomistic behavior and the growth mode were explained in terms of the surface energy and the effect of segregated Ge as a surfactant.
In the Si VPE on Si(100)-(2 x 1), Ge(100)-(2 x 1), and Ge(111)-c(2 x 8) using disilane, STM images resolved the adsorption geometry of individual dissociated fragments, ordering kinetics, and grown film morphology. By combining information from the core-level spectroscopy, the STM images, and the electron diffraction results, a detailed description of adsorption, thermal reactions, and hydrogen desorption proceeded during VPE was obtained. An "atomic layer epitaxy" (ALE) process was also developed to grow epitaxial Si layerwise at temperatures as low as 820 K.
|Rights Information:||Copyright 1994 Lin, Deng-Sung|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI9503256|