Speaker
Description
VO$_2$ films on the relaxor ferroelectric Pb(Mg$_{1/3}$Nb$_{2/3}$)$_{0.72}$Ti$_{0.28}$O$_3$ (PMN-PT) provide a promising candidate for the realization of a “Mott-tronic” device. VO$_2$ undergoes a first-order structural phase transition at about 340 K and simultaneously switches from insulating to metallic behavior by a five orders of magnitude resistance drop. Importantly, the insulator-to-metal transition can also be driven by out-of-plane compressive lattice strain as being mediated, for example, by a PMN-PT substrate.
Here, we present a hard x-ray photoelectron spectroscopy (HAXPES) study of the electronic structure of VO$_2$/PMN-PT interfaces across the strain- and temperature-induced phase transition. The in operando monitoring of the shapes and positions of characteristic core-level emissions directly reveals strain-dependent changes of the electronic structure and phase transition temperature of the VO$_2$ film as well as bias-dependent changes of the electronic energy-level alignment at the VO$_2$/PMN-PT interface.
Overall, our results establish HAXPES as a powerful tool for the in operando investigation of functional oxide interfaces.
