@misc{SchmeisserHaeberle, author = {Schmeißer, Dieter and Haeberle, J{\"o}rg}, title = {Intrinsic localized gap states in IGZO and its parent single crystalline TCOs}, series = {Thin Solid Films}, journal = {Thin Solid Films}, number = {603}, issn = {0040-6090}, doi = {10.1016/j.tsf.2016.02.010}, pages = {206 -- 211}, abstract = {We report on the X-ray absorption data for Indium-Gallium-Zink-Oxide thin films, amorphous ZnO films, amorphous SnOx films, and single crystalline In2O3, Ga2O3, ZnO, and SnO2 data. These absorption data probe the empty conduction band states explicitly. Also they allow for an elemental assignment using resonant excitation to derive the contributions of each metal ion. We find that the lowest states appear right at the Fermi energy and result from configuration interaction induced charge transfer states which we consider as intrinsic gap states.}, language = {en} } @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{GarainBarmanSinhaetal., author = {Garain, Samiran and Barman, Koushik and Sinha, Tridib Kumar and Jasimuddin, Sk and Haeberle, J{\"o}rg and Henkel, Karsten and Schmeißer, Dieter and Mandal, Dipankar}, title = {Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction}, series = {ACS Applied Materials and Interfaces}, volume = {8}, journal = {ACS Applied Materials and Interfaces}, number = {33}, issn = {1944-8244}, doi = {10.1021/acsami.6b05236}, pages = {21294 -- 21301}, abstract = {Exploring efficient and inexpensive electrocatalysts for the oxidation of water is of great importance for various electrochemical energy storage and conversion technologies. In the present study, a new water-soluble [Ce III(DMF) (HSO4)3] complex was synthesized and characterized by UV-vis, photoluminescence, and high-resolution X-ray photoelectron spectroscopy techniques. Owing to classic 5d →4f transitions, an intense photoluminescence in the UV region was observed from the water-soluble [CeIII(DMF (HSO4)3] complex. A stacking electrode was designed where self-assembled L-cysteine monolayer modified gold was immobilized with the synthesized cerium complex and was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltam-metry. The resulting electrode, i.e., [CeIII(DMF)(HSO4)3]-L-cysteine-Au stacks shows high electrocatalytic water oxidation behavior at an overpotential of η ≈0.34 V under neutral pH conditions. We also demonstrated a way where the overpotential is possible to decrease upon irradiation of UV light.}, 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} } @phdthesis{Haeberle, author = {Haeberle, J{\"o}rg}, title = {Transparente leitf{\"a}hige Metalloxideinkristalle und amorphe oxidische D{\"u}nnschichtsysteme - Eine photoelektronenspektroskopische Vergleichsstudie}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-40356}, pages = {137}, abstract = {Die Materialklasse der transparenten leitenden Metalloxide (engl. transparent conducting oxides (TCO)) und amorphen oxidischen D{\"u}nnschichtsysteme (engl. amorphous oxidic semiconductors (AOS)) sind {\"u}beraus faszinierend, da sie gegens{\"a}tzliche physikalische Eigenschaften, wie Transparenz und hohe Leitf{\"a}higkeit in sich vereinen. Die zugrunde liegenden physikalischen Mechanismen sind immer noch unklar und werden in dieser Dissertation beleuchtet. Dazu wurde die resonante Photoelektronenspektroskopie (resPES)gew{\"a}hlt, da sie sich in den letzten Jahren als vielseitiges Werkzeug f{\"u}r die detaillierte Untersuchung der elektronischen Struktur und der Identifikation von Defekten ausgezeichnet hat. Im Rahmen dieser Arbeit ergab sie die einmalige M{\"o}glichkeit, sowohl hoch qualitative TCO-Einkristalle (ZnO, Ga2O3, In2O3 und SnO2) als auch amorphe oxidische D{\"u}nnschichtsysteme (GIZO und SnOx) photeelektronenspektroskopisch zu untersuchen und zu vergleichen. Somit wird gezeigt, dass die elektronische Struktur der Materialklasse der TCO und ihrer korrespondierenden AOS mehr Gemeinsamkeiten aufweisen, als bisher erwartet wurde. Es zeigt sich, dass die Bandl{\"u}cke, im eigentlichen Sinne, in der Materialklasse der TCO und AOS nicht existiert. Lokalisierte Zust{\"a}nde f{\"u}llen den gesamten Bereich dieser Bandl{\"u}cke aus und reichen zum Teil in das Valenzband (VB) und Leitungsband (CB) hinein. Dies f{\"u}hrt dazu, dass es keine, wie bisher gedacht, scharfen Grenzen zwischen lokalisierten und delokalisierten Zust{\"a}nden gibt. Um dies zu verdeutlichen wird ein neuartiges Modell eingef{\"u}hrt, das aufzeigt, dass die Wechselwirkung von metallischen d- und s-Niveaus in einer {\"O}ffnung der d-Schale resultiert. Durch Charge-Transfer (CT)-Mechanismen und weitere Hybridisierung mit metallischen unbesetzten p-Zust{\"a}nden folgt eine st{\"a}rkere Lokalisierung. Die Diskussion wird begonnen mit der Kl{\"a}rung der Elementeverh{\"a}ltnisse der untersuchten Materialsysteme. Darauf folgt die Charakterisierung von intrinsischen Defekten und ihren Beitr{\"a}gen auf die elektronische Struktur. Abschließend werden die elektronischen Strukturen der AOS mit denen der korrespondierenden TCO verglichen.}, language = {de} }