Fabrication of Multi-Layred Thin Film Structure by Photo-induced Catalytic Reactions of Organometallic Compounds

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We have investigated a method of fabricating multi-layred ultra-thin film structure by photoinduced catalytic reactions of organomatallic compounds on solid surfaces. We utilized ultraviolet (UV) and vacuumultraviolet (VUV) lights as the exciting light source.We have investigated the photo-induced reactions of organic compounds such as tetramethylsilane (TMS) and its hydrogen-sustitued compounds which take place on Si surfaces. These compounds are precurcers for wide-gap semiconductor silicon carbide, SiC.We confirmed that amorphous SiC is formed on the Si surface by the photodecomposition and subsequent photopolymerization of TMS.We also demonstrated with IR measurements that the C-H bonds of TMS are decomposed by VUV irradiation through two reaction pathways : one is the primary photodecomposition and the other is the secondary process in which photofragments react with TMS.The metal/GaAs interface reaction which occurs during the deposition of metals on GaAs have been investigated using synchrotron-radiation photoemission spectroscopy, x-ray diffraction, and Rutherford backscattering spectroscopy. We found that diffusion and aggregation of metal atoms at the metal/GaAs interface proceeds in different manners depending on the metal deposited and the surface chemical state of the GaAs substrate. We also revealed that CaF_2 epitaxially grows on the sulfur-treated GaAs surface, while the traditional acid treatment of the surfaceleads to formation of amorphous CaF_2