Metal-insulator transition in crystalline V2O3 thin films probed at atomic-scale using emission Mossbauer spectroscopy

Microscopic understanding the metal-to-insulator transition (MIT) in strongly correlated materials is critical to the design and control of modern "beyond silicon" Mott nanodevices. In this work, the local MIT behaviors in single crystalline V2O3 thin films were probed on an atomic scale by online Fe-57 emission Mossbauer spectroscopy (eMS) following dilute (<10(-3) at.%) implantation of Mn-57(+) (T-1/2 = 90 s). Both the epitaxial and the textured V2O3 thin films grown by direct current magnetron sputtering were studied. Three structural components were resolved and identified in the eMS spectra with parameters characteristic of Fe in the 2+ valence state, which are attributable to Fe in either lattice damage or structural defects and Fe in the intrinsic crystal structure of V2O3, respectively. The results prove that the oxygen vacancies are common in the V2O3 thin films. With co-existence of both the non-stoichiometry and epitaxial strain in the thin films, the epitaxial strain plays a dominant role in controlling the global MIT properties of the film. The atomic scale structural transition captured by the eMS affirms the early-stage dynamics of the MIT of V2O3 thin film reported previously. These results approve the feasibility to tune the electronic transport of the V2O3 thin films for the next-generation Mott nanodevices by the epitaxial strain via the sample growth parameters.