The effect of oxygen flow rate on metal–insulator transition (MIT) characteristics of vanadium dioxide (VO₂) thin films by pulsed laser deposition (PLD)

Vanadium dioxide (VO₂), because of its unique metal–insulator phase transion around room temperature, has enormous potential for applications in thermochromic, electrochromic, microbolometery, and non-volatile switches. However, obtaining phase-pure VO₂ has been challenging due to its narrow window of thermodynamic stability. Pulsed laser deposition (PLD) is considered to be one of the most promising technique to deposit phase-pure VO₂ thin films. While optimizing PLD processing parameters, (such as oxygen pressure (P_O2), substrate temperature (T_s), laser energy (E_L), target-substrate distance (d_T-S), and laser repetition rate (RR)) is crucial, and their effects have been reported, the effect of gas flow rate (Q_O2) has been largely neglected. Since the Q_O2 and P_O2 of the PLD system are intertwined at the outset, most reports are focused only on either Q_O2 or P_O2. We report on the effect of gas flow rate under constant P_O2, on the quality of the VO₂ thin films. Controlling flow rate affected the resistivity contrast between the metallic and insulator phases, the temperature ranges of the transition, and the width of hysteresis. We anticipate that this study will help set the standard for obtaining high quality VO₂ thin films.