@misc{HaeberleMachulikJanowitzetal., author = {Haeberle, J{\"o}rg and Machulik, Stephan and Janowitz, Christoph and Manzke, Recardo and Gaspar, Diana and Barquinha, Pedro and Schmeißer, Dieter}, title = {Gap states in the electronic structure of SnO2 single crystals and amorphous SnOxthin films}, series = {Journal of Applied Physics}, volume = {120}, journal = {Journal of Applied Physics}, number = {10}, issn = {0021-8979}, doi = {10.1063/1.4962313}, pages = {105101-1 -- 105101-13}, abstract = {The electronic structure of a SnO2 single crystal is determined by employing resonant photoelectron spectroscopy. We determine the core level, valence band, and X-ray absorption (XAS) data and compare these with those of amorphous SnOx thin films. We find similar properties concerning the data of the core levels, the valence band features, and the absorption data at the O1s edge. We find strong signals arising from intrinsic in-gap states and discuss their origin in terms of polaronic and charge-transfer defects. We deduce from the XAS data recorded at the Sn3d edge that the Sn4d10 ground state has contributions of 4d9 and 4d8 states due to configuration interaction. We identify localized electronic states depending on the strength of the 4d-5s5p interaction and of the O2p-to-Sn4d charge-transfer processes, both appear separated from the extended band-like states of the conduction band. For the amorphous SnOx thin films, significant differences are found only in the absorption data at the Sn3d-edge due to a stronger localization of the in-gap states.}, language = {en} } @misc{HaeberleBrizziGasparetal., author = {Haeberle, J{\"o}rg and Brizzi, Simone and Gaspar, Diana and Barquinha, Pedro and Galazka, Zbigniew and Schulz, Detlev and Schmeißer, Dieter}, title = {A spectroscopic comparison of IGZO thin film and the parent In2O3, Ga2O3, and ZnO single crystals}, series = {Materials Research Express}, volume = {3}, journal = {Materials Research Express}, number = {10}, issn = {2053-1591}, doi = {10.1088/2053-1591/3/10/106302}, pages = {106302-1 -- 106302-17}, abstract = {We use resonant photoelectron spectroscopy at the Zn 2p, Ga 2p, In 3d, and O 1s absorption edges to report on the electronic properties of indium-gallium-zinc-oxide thin films. We also compare the data with the respective data of the corresponding single crystals In2O3, Ga2O3, and ZnO. We focus on the elemental composition and, in particular, find no evidence for oxygen deficiency. The In, Ga, and Zn absorption data at resonance can be used to analyze the conduction band states in detail. We deduce that a configuration interaction between d10s0 and d9s1states is of importance. We provided a novel mechanism in which configuration interaction induced gap states create both, extended unoccupied states around E F as well as localized occupied states within the gap.}, language = {en} }