Investigation of the interfaces of silicon-silicon dioxide thin films and ball-milled tin-germanium (silicon) powders using x-ray techniques
The Si/So{sub 2} thin film interface and Sn/Ge(Si) interfaces in ballmilled Sn-Ge(Si) powders are investigated using x-ray reflectivity and EXAFS, respectively. X-ray reflectivity is used to compare the silicon dioxides grown on Si wafers, using conventional thermal oxidation an Plasma Enhanced Chemical Vapor Deposition (PECVD) processes. The aim was to determine the film morphology of PECV-deposited silicon dioxides, where a considerable decrease in deposition temperature is achieved. Macroscopic properties, such as film density, thickness, surface and interface roughness are probed. Analysis was carried out using several thermally grown and PECV-deposited oxides. Both techniques are found to produce silicon dioxides of good quality although the interface roughness of the PECV-deposited oxides was relatively higher. Sn K-edge EXAFS measurements were used to examine the Sn/Ge(Si) interface in ball-milled Sn-Ge(Si) powders. X-ray diffraction and Differential Scanning Calorimetry were also used as supporting techniques. Measurements made on samples of varying Sn concentrations showed systematic changes reflecting the fact that Sn appears in two different states, the metallic ({beta}-Sn) phase, and a cubic SnGe(Si) alloy phase formed at the Sn/Ge(Si) interface. In the case of the Sn-Ge system, where the Sn concentration is 20 vol. %, the alloy phase was dominant leaving essentially no Sn in the normal {beta}-Sn phase. Alloying included several monolayers, and the bonding showed a strong covalent nature with stability above the bulk melting point of Sn. The results can be used to explain the previously observed reductions in melting enthalpy. Alloying at the Sn/Si interface is also strongly covalent, even though the reaction was less extensive. The thickness of the alloy phase is only about a monolayer. This difference was attributed to the higher lattice mismatch between Sn and Si.
- Research Organization:
- City Univ. of New York, NY (United States)
- OSTI ID:
- 121192
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1993
- Country of Publication:
- United States
- Language:
- English
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