Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Si core level X-ray Absorption Fine Structures (XAFS) spectroscopy has been used to study, in the gas phase, the structure and bonding of a series of highly symmetric organosilicon compounds, Si(CH{dollar}\sb3)\sb4{dollar} (TMS), Si{dollar}\rm\sb2(CH\sb3)\sb6{dollar} (HMDS), Ge (Si(CH{dollar}\sb3)\sb3\rbrack\sb4{dollar} (GESI4), Si (Ge(CH{dollar}\sb3)\sb3\rbrack\sb4{dollar} (SIGE4), and Si (Si(CH{dollar}\sb3)\sb3\rbrack\sb4{dollar} (SISI4), which can be used as model compounds for silicon-germanium electronic materials.;The Si K- and L{dollar}\sb{lcub}2,3{rcub}{dollar}-edge X-ray absorption near edge structure (XANES) of HMDS, GESI4 SIGE4 and SISI4 have been recorded with synchrotron radiation and calculated by the multiple-scattering (MS) X{dollar}\alpha{dollar} method. It is found that there is a significant difference in the absorption coefficient in the near-edge region between local Si-Si interactions in these compounds and long range Si-Si interactions in crystalline solids. Both the experiment and the calculation show that, (a) Si-Si and Si-Ge are quite similar in shaping the pre-edge XANES for the three compounds, SIGE4, GESI4 and SISI4, which have identical molecular symmetry; (b) the XANES are different for HMDS and GESI4, where the local bonding is similar; the same is observed for SIGE4 and Si (100) crystal. Therefore, XANES is very sensitive not only to the local structure (nearest neighbours interaction) of the absorbing atom, but also to the extended structure (long range interaction). Based on the calculation results and the comparison of the gas phase and solid state L{dollar}\sb{lcub}2,3{rcub}{dollar}-edge spectra of HMDS, the low-lying energy features are assigned to transitions to mostly valence orbitals.;The extended X-ray Absorption Fine Structures (EXAFS) for TMS, HMDS, GESI4, SIGE4 and SISI4 compounds have also been recorded in the gas phase and analyzed by curve-fitting method. The Si-Ge bond lengths in SIGE4 and GESI4 are found to be 2.38(3) A and 2.396(15) A respectively. The comparison of the Si-Si and Si-Se interatomic distances in crystalline solids has been made.;Valence band photoelectron spectra have been assigned with the aid of MS-X{dollar}\alpha{dollar} calculation and the photon dependence of the intensities for TMS, HMDS, SISI4, GESI4 and a cyclic compound (Si(CH{dollar}\sb3)\sb2\rbrack\sb6{dollar} (DCHS). The correlation between the binding energy of the highest occupied molecular orbital measured by photoelectron spectroscopy and the inflection energy in K- and L{dollar}\sb{lcub}2,3{rcub}{dollar}-edge XANES is discussed.



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