Vanadium oxide thin films with extremely narrow thermal hysteresis loop width were obtained by Ta doping for THz modulation applications

Abstract Based on the application potential of VO2 thin film in THz modulation field, only keeping its modulation amplitude is no longer applicable, and the film also needs to have lower phase transition temperature and narrower loop width, etc. In order to solve this problem, and since the high valence ion doping can reduce the phase transition temperature of VO2 films, the effect of Ta5+ doping on the phase transition performance of VO2 films is studied and analyzed in this paper. In this work, based on DC reactive magnetron sputtering technology, un-doped and Ta-doped VO2 films were prepared on high-resistance silicon substrate by two-step method. The microstructure of VO2 films before and after Ta doping was characterized by XPS, XRD and SEM images to assist the study and analysis of the influence of Ta5+ ions on the crystal phase structure of VO2. Finally, when the doping concentration of Ta5+ is 0.71%, the phase transition temperature (TC) of VO2 film decreases to 37.5 °C , the loop width ( Δ H ) narrows to 1.03 °C , and the optical modulation amplitude is maintained at 64.2%, which makes it more suitable for THz modulator.