Electronic structure of V O2 / Ti O2: Nb upon photocarrier injection

We study the photocarrier injected electronic structure of V O2 / Ti O2: Nb (≡p-n junction) thin-film heterostructure using photoemission spectroscopy, across the temperature-dependent metal-insulator transition in V O2. The valence band of V O2 shifts systematically to higher binding energy upon photocarrier injection (PCI). In the insulating phase, the energy shift as a function of irradiated power matches the surface photovoltage (SPV) behavior, while in the metallic phase, the energy shift follows the SPV trend but is reduced due to recombination. The temperature dependence of the energy shift between 200 and 330 K varies nearly linearly with the SPV. The study provides evidence for hole doping from Ti O2: Nb to V O2 by the PCI effect.