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- ItemExperimental electronic structure of In2O3 and Ga2O3(Bristol : IOP, 2011) Janowitz, C.; Scherer, V.; Mohamed, M.; Krapf, A.; Dwelk, H.; Manzke, R.; Galazka, Z.; Uecker, R.; Irmscher, K.; Fornari, R.; Michling, M.; Schmeißer, D.; Weber, J.R.; Varley, J.B.; Van De Walle, C.G.Transparent conducting oxides (TCOs) pose a number of serious challenges. In addition to the pursuit of high-quality single crystals and thin films, their application has to be preceded by a thorough understanding of their peculiar electronic structure. It is of fundamental interest to understand why these materials, transparent up to the UV spectral regime, behave also as conductors. Here we investigate In2O3 and Ga2O3, two binary oxides, which show the smallest and largest optical gaps among conventional n-type TCOs. The investigations on the electronic structure were performed on high-quality n-type single crystals showing carrier densities of ∼1019 cm-3 (In2O3) and ∼1017 cm-3(Ga2O3). The subjects addressed for both materials are: the determination of the band structure along high-symmetry directions and fundamental gaps by angular resolved photoemission (ARPES). We also address the orbital character of the valence- and conduction-band regions by exploiting photoemission cross.
- ItemDynamics of graphene growth on a metal surface: A time-dependent photoemission study(Milton Park : Taylor & Francis, 2009) Grüneis, Alexander; Kummer, Kurt; Vyalikh, Denis V.Applying time-dependent photoemission we unravel the graphene growth process on a metallic surface by chemical vapor deposition (CVD). Graphene CVD growth is in stark contrast to the standard growth process of two-dimensional films because it is self-limiting and stops as soon as a monolayer of graphene has been synthesized. Most importantly, a novel phase of metastable graphene was discovered that is characterized by permanent and simultaneous construction and deconstruction. The high quality and large area graphene flakes are characterized by angle-resolved photoemission, proving that they are indeed monolayer and cover the whole 1×1 cm Ni(111) substrate. These findings are of high relevance to the intensive search for reliable synthesis methods for large graphene flakes of controlled layer number.