Improving phase transition temperature of VO <sub>2</sub> via Ge doping: a combined experimental and theoretical study
Lin Wang, Yuqi Hao, Wei Ma, Sen Liang
Abstract
Abstract Enhancing the semiconductor–metal phase transition temperature ( T SMT ) of VO 2 is of great consequence for further exploring the potential applications of VO 2 at elevated temperatures. In this study, Ge 4+ ‐doped VO 2 (Ge x V 1− x O 2 ) samples were prepared by the hydrothermal and annealing approach. X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HRTEM), differential scanning calorimetry (DSC) and resistivity–temperature ( R ‐ T ) analyses were used to investigate the influence of Ge doping on the lattice structures and phase transition properties of Ge x V 1– x O 2 samples. We found that the lattice parameter of Ge x V 1− x O 2 decreased with the Ge concentration increasing from 2 at% to 18 at%, which was further supported by density functional theory (DFT)‐based first‐principle simulations. T SMT firstly increased from 64.5 to 73.0 °C at 8 at% Ge and then decreased to 71.5 °C at higher Ge concentration. Furthermore, DFT analysis revealed that the impact of lattice distortion induced by Ge doping rather than the changes in electronic structure is more pronounced on modulating T SMT of Ge x V 1− x O 2 . The present work has pointed out the direction that the T SMT could be enhanced and illustrated the physical reason behind the regulation of T SMT in ions‐doped VO 2 systems.