Julie Karel, Carlos E. ViolBarbosa, Janos Kiss, Jaewoo Jeong, Nagaphani Aetukuri, Mahesh G. Samant, Xeniya Kozina, Eiji Ikenaga, Gerhard H. Fecher, Claudia Felser, and Stuart S. P. Parkin, "Distinct Electronic Structure of the Electrolyte Gate-Induced Conducting Phase in Vanadium Dioxide Revealed by High-Energy Photoelectron Spectroscopy," ACS Nano 8 (6), 5784-5789 (2014).
The research in memristors and liquid electrolyte gating devices, where interfacial electric field induces modification throughout the film, requires spectroscopy investigation with large probe depth. HAXPES is the ideal technique to study these systems. We investigated the 3d orbital ordering of a VO2 thin film before and after been gated by ionic liquid electrolyte. The dependence of the photoemission intensity on the direction of the light electric field indicates a reduced orbital polarization in the gated state with respect to the monoclinic phase. A smaller orbital polarization is a direct consequence of the reduced vanadium dimerization, as shown schematically .