A Novel Reactive Element Doping Strategy for Metal Oxides Using Pulsed Laser Deposition: Demonstration with Sulphur in VO2

Vanadium dioxide (VO2) is a phase transition material with significant potential for applications in electrical and optical devices, owing to its remarkable properties such as a sharp change in resistivity and infrared transmittance during the phase transition. Lowering the transition temperature (Tc) while maintaining a high transition amplitude is crucial to many applications; however, conventional doping elements often compromise its transition amplitude. Recent simulations suggest that chalcogen doping, particularly with sulphur, could effectively tune Tc without diminishing the transition performance. Sulphur doping, however, poses challenges due to the tendency of sulphur to react with oxygen during VO2’s high-temperature deposition process, forming volatile sulphur oxides that are lost in the vacuum system. This study introduces a novel sulphur doping approach for VO2 by using pulsed-laser deposition (PLD) from a V2S3 target. By varying the laser repetition rate, sulphur incorporation was precisely controlled without inducing significant defects. Sulphur doping reduced Tc by up to 44.3 °C/at.%, one of the most efficient reductions reported. However, higher sulphur concentrations led to reduced electrical and optical contrast, attributed to grain boundary strain and disorientation. Lower laser repetition rates facilitated uniform grain growth, sharpening phase transitions and narrowing hysteresis widths. This study underscores the importance of deposition parameters in optimising VO2 properties and demonstrates the potential of PLD-based strategies for incorporating reactive elements into metal oxides. Future research should further investigate the distinct mechanisms of sulphur doping to refine material properties for advanced applications.