Room temperature tunability of Mo-doped VO 2 nanofilms across semiconductor to metal phase transition

Abstract The phase transition temperature ( T t ) across semiconductor-to-metal transition (SMT) of the vanadium dioxide (VO 2 ) thin films can be tuned to room temperature either by reducing the grain size of crystallites to nanoscale or by doping them with molybdenum (Mo 6 + ) 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%) Mo 6 + -doped VO 2 nanofilms across SMT. Room temperature value of T t = 303.7 K was achieved for Mo 6 + -doped VO 2 nanofilms as compared to 333.2 K of pristine VO 2 nanofilms and against 340 K of bulk VO 2 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 Mo 6 + -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 ( R s /R M ) and hysteresis width (Δ H ) diminished whereas hysteresis sharpness (Δ T ) escalated across SMT with the increase of Mo + 6 -ions.