Role of surface termination in the metal-insulator transition of V$_2$O$_3$(0001) ultrathin films

Abstract

Surface termination is known to play an important role in determining the physical properties of materials. It is crucial to know how surface termination affects the metal-insulator transition (MIT) of V2O3 films for both fundamental understanding and its applications. By changing growth parameters, we achieved a variety of surface terminations in V2O3 films that are characterized by low energy electron diffraction (LEED) and photoemission spectroscopy techniques. Depending upon the terminations, our results show MIT can be partially or fully suppressed near the surface region due to the different filling of the electrons at the surface and sub-surface layers and change of screening length compared to the bulk. Across MIT, a strong redistribution of spectral weight and its transfer from high-to-low binding energy regime is observed in a wide-energy-scale. Our results show total spectral weight in the low-energy regime is not conserved across MIT, indicating a breakdown of 'sum rules of spectral weight', a signature of a strongly correlated system. Such change in spectral weight is possibly linked to the change in hybridization, lattice volume (i.e., effective carrier density), and spin degree of freedom in the system that happens across MIT. We find that MIT in this system is strongly correlation-driven where the electron-electron interactions play a pivotal role. Moreover, our results provide a better insight in understanding the electronic structure of strongly correlated systems and highlight the importance of accounting surface effects during interpretation of the physical property data mainly using surface sensitive probes, such as surface resistivity.