Room temperature tunability of Mo-doped VO2 nanofilms across semiconductor to metal phase transition

The phase transition temperature (Tt) across semiconductor-to-metal transition (SMT) of the vanadium dioxide (VO2) thin films can be tuned to room temperature either by reducing the grain size of crystallites to nanoscale or by doping them with molybdenum (Mo6 +) ions. In this work, the combined response of these effects (quantum size effect and doping mechanism) has been demonstrated by studying the structural and electrical transport properties of low concentration (0, 1, 3 and 5%) Mo6 +-doped VO2 nanofilms across SMT. Room temperature value of Tt = 303.7 K was achieved for Mo6 +-doped VO2 nanofilms as compared to 333.2 K of pristine VO2 nanofilms and against 340 K of bulk VO2 thin films. A systematic analysis of charge carrier mobility (μ), Seebeck coefficient (s) and charge carrier concentration (n) was performed for the first time to the best knowledge of the authors. Decrease in μ and increase in s were observed across SMT with increase in doping percentage of Mo6 +-ions. n increased by 1 to 4 orders of magnitude across SMT for the samples which contributed almost entirely for the resistance change. Resistance ratio (Rs/RM) and hysteresis width (ΔH) diminished whereas hysteresis sharpness (ΔT) escalated across SMT with the increase of Mo+ 6-ions.