Regulating the phase transition temperature of VO2 films via the combination of doping and strain methods

Abstract

Phase change materials have the potential for reversible modulation of the physical and chemical properties of other materials, making them suitable for a wide range of applications. Among these phase change materials, VO2 is particularly attractive for electronic applications due to its ultrafast reversible phase transition at near room temperature (68 °C). Regulating the phase transition temperature of VO2, however, remains a challenge. In this study, two factors, i.e., film thickness and buffer layer, that can effectively regulate the phase transition temperature of VO2 films were introduced, and the effect of doping on the phase transition temperature was also investigated. The interfacial strain between the VO2 film and substrate was modulated by adjusting the film thickness and doping concentration in the buffer layer. This was to explore the effect of strain on the phase transition temperature of the film. Changes in VO2 lattice parameters were reflected by the shifts of XRD diffraction peaks. Test and measurement results show that the phase transition temperature of VO2 gradually increased as the interfacial strain increased. For instance, the phase transition temperature (Th) of the GeVO/AlGeO-3 sample reached 91.2 °C. Moreover, some samples exhibited increased abrupt parameters, such as phase transition amplitude and thermal hysteresis width. These findings have important implications for the use of VO2 materials in applications, including switches, sensors, and amnesic resistors.