Quantitative Study of Reversible Nonvolatile VO₂ Thin Films Through Plasma Driven Phase Engineering Process

The nanoscale control of phase transition in correlated materials offers significant insight into phase transition dynamics for the advancement of future nanoelectronics devices. This study explores the phase transition phenomenon in vanadium dioxide (VO₂), focusing on the heterogeneous phases evolved after low-pressure plasma irradiation on VO₂ thin films, a strong electron-correlated material. The modulation in the Argon (Ar) plasma power reveals the formation of homogeneous and heterogeneous phases with variable resistive states at room temperature. High-resolution transmission electron microscopy (HRTEM) is observed with the change in interplanar spacing revealing monoclinic (M1) at 0W, monoclinic-tetragonal rutile (phase coexistence, M1-R) at 50W, and tetragonal rutile (R) at 90W. Dielectric force microscopy (DFM) shows distinct dielectric responses corresponding to different phases, characterized by potential differences of 3 mV (M1), 5 mV (M1-R), and 7.44 mV (R) phases. The coexistence of M1-R phase is stabilized and examined at room temperature, with variations in the charge carrier density observed relative to M1 and R phases individually. The phase change in VO₂ is found to be reversible, enabling stable resistive states even after the plasma is removed. The changes in plasma geometry help find and stabilize unstable phases, which can be useful in nanoelectronics.