文摘
Tailoring effectively the hysteresis loop width of VO2 semiconductor-metal transition (SMT) is crucial to develop thermal sensor devices. The Ti-doping is known as the most effective method to reduce 螖Tc and has been considered as the prototypical model in understanding the mechanism by which the 螖Tc of VO2 MST could be manipulated. Here we present a joint experimental and first-principles computational study on nondoped and Ti-doped VO2 to clarify the mechanism of Ti-doping on narrowing the hysteresis loop width of VO2. On the basis of the analyses of differential scanning calorimetry (DSC), we found that phase transition temperatures in the cooling circle increase faster than those in the heating circle with increasing Ti concentrations, exhibiting a hysteresis width reduction at 2 掳C per Ti at. %. First-principles calculations reveal that dopant Ti atoms break the octahedral symmetry of local structure in VO2 (R) phase. This distortion is propagated in anisotropy and exhibits an obvious nonlocal effect. In contrast, the Ti-doping-induced structural change in VO2 (M) phase is only constrained in Ti-involved chain along the a-axis. The calculated energy profiles for TixV1鈥?i>xO2 phase transition shows that structural stability and activation energies increased with the increase of Ti concentration. The activation barriers in Ti-doped VO2 (R) phases are increased more remarkably than that in Ti-doped VO2 (M) phases, which is consistent with experimental observation of concentration-dependent reduction of thermal hysteresis width.