It was demonstrated experimentally that doping Zr into TiAlN coatings at room temperature will detriment its oxidation resistance. On the other hand, there are evidences that doping Zr into TiAlN at high temperature will improve coating's oxidation resistance. In the present work, we address the effect of Zr on the oxidation resistance of TiAlN by means of ab initio molecular dynamics simulations. The TiAlN and TiAlZrN (1 Zr atom replacing 1 Ti atom) surfaces covered with 4 oxygen atoms at 300K and 1123K were simulated. Based on the analysis of the atomic motion, bond formation after relaxation, and the charge density difference maps we find that at 300K, the addition of Zr induces escape of Ti atoms from the surface, resulting in formation of surface vacancies and subsequently TiO 2. Comparison of metal-oxygen dimers in the vacuum and above the TiAlZrN surface further shows that the addition of Zr in the TiAlN surface will change the lowest bonding energy sequence from Zr-O < Ti-O < Al-O in the vacuum to Ti-O < Zr-O < Al-O above the TiAlZrN surface.

Pi, Tun-Wen, "Synchrotron radiation photoemission study of metal overlayers on hydrogenated amorphous silicon at room temperature " (1990). Retrospective Theses and Dissertations. 11214. http://lib.dr.iastate.edu/rtd/11214 UMI MICROFILMED 199Ô ^ INFORMATION TO USERSThe most advanced technology has been used to photograph and reproduce this manuscript from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer.The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction.In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion.Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book.Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. 1990Signature was redacted for privacy.Signature was redacted for privacy.Signature was redacted for privacy.Signature was redacted for privacy.ii INTRODUCTIONComprehending completely the metal-silicon interface is a challenge, not only for academic reasons but for improved industrial application. The complexity of interfaces is related to the fact that reactions occur mostly at temperatures well below the temperature required to form silicides.Moreover, the interfacial phenomena are strongly dependent on characteristics of the electronic properties of metal deposits. No models can then uniquely describe the interface reaction [1]. For example, the interaction with Si is weak for the noble metals whose d-shell is closed.However, despite the fact that Au and Ag do not form stable silicides. Au intermixes severely with Si, whereas Ag/Si is an abrupt interface. For other metals like Cr with an unfilled d-band, various forms of silicides are possible, from a metal-rich silicide (CrgSi) to a Si-rich silicide (CrSia).To date numerous studies have been done particularly for metals on single-crystal silicon (c-Si) as a substrate. However, information on metals on amorphous substrates is limited. In this dissertation, metals deposited on a hydrogenated amorphous silicon (a-Si:H) film at room temperature are studied. The purpose of this work is mainly understanding the electronic properties of the...

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