Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 24: Focus Session: Structure and Chemistry of Metal-Oxide Surfaces I
O 24.2: Talk
Tuesday, March 13, 2018, 11:00–11:15, MA 005
Vanadium dioxide as high work function electrode — •Rongbin Wang1,2, Keke Fu1, Takayoshi Katase3,4, Hiromichi Ohta3, Steffen Duhm1, and Norbert Koch1,2 — 1Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, China — 2Institut für Physik, Humboldt-Universität zu Berlin, Germany — 3Research Institute for Electronic Science, Hokkaido University, Japan — 4Laboratory for Materials and Structures, Tokyo Institute of Technology, Japan
VO2 is a rather unique metal oxide as it exhibits a first-order metal-insulator (MI) transition from an insulating phase with monoclinic structure to a metallic phase with tetragonal rutile structure near 340K. The evolution of valence bands and core levels of VO2 thin films upon sputtering and annealing with or without residual O2 atmosphere was monitored by ultraviolet and X-ray photoemission spectroscopy. Sputtering and subsequent annealing in vacuum introduced lower oxidation state V species, leading to an increased density of V 3d derived bands close to the Fermi level. However, annealing under O2 results in stoichiometric VO2 with a high work function of up to 6.7 eV. In addition, the temperature dependent photoemission results illustrate the electronic structure evolution of VO2 during the metal-insulator transition.