@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} } @inproceedings{HaeberleRichterSchmeisseretal., author = {Haeberle, J{\"o}rg and Richter, Matthias and Schmeißer, Dieter and Galazka, Zbigniew and Janowitz, Christoph}, title = {Resonant Photoemission at the O1s threshold to characterize In2O3 single crystals}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {We report on spectroscopic investigations on In2O3 single crystals. We focus on the detailed analysis of the O1s resonance profile by resonant photoelectron spectroscopy (resPES). From these we analyze the electronic structure and assign the O2p- and In5sp state to build the valence band and the conduction band in different contributions, respectively. This is deduced from constant final state spectra on the O-KLL-Auger along the O K-edge and In M4,5-edge and a comparison to the corresponding X-ray absorption spectroscopy data. We also identify several types of defects. A broad band of oxygen derived defects is identified in the valence band and extends throughout the gap. Small polarons are attributed to cause an anti-resonance in the constant initial states around the O1s threshold. In addition, an Auger decay separated by the O-KLL is present at O-K resonance and indicates the existence of localized charge transfer states which involves In5sp states. Finally, we are able to distinguish two different oxygen species from the resPES data. One corresponds to theintrinsic In2O3 structure and the other is a non-corresponding species.}, 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} } @incollection{HenkelHaeberleMuelleretal., author = {Henkel, Karsten and Haeberle, J{\"o}rg and M{\"u}ller, Klaus and Janowitz, Christoph and Schmeißer, Dieter}, title = {Preparation, properties and electronic structure of SnO₂}, series = {Single Crystals of Electronic Materials}, booktitle = {Single Crystals of Electronic Materials}, editor = {Fornari, Robert}, publisher = {Elsevier, Woodhead Publishing}, address = {Duxford}, isbn = {978-0-08-102096-8}, pages = {547 -- 572}, abstract = {This chapter reports about tin oxide (SnO₂), a material which belongs to the transparent conducting oxide family and is best characterized by its high conductivity, high carrier mobility, and the ability to form p-type conductivity. We correlate these properties in terms of localized intrinsic electronic defect states which are resolved by resonant photoelectron spectroscopy measurements. We describe SnO₂ in terms of an inhomogeneous, mixed-ionic-covalent semiconductor in which these intrinsic electronic defects state are stabilized.}, language = {en} }