Broad Range Tuning of Phase Transition Property in VO₂ Through Metal-Ceramic Nanocomposite Design

Vanadium dioxide (VO₂) is a well-studied Mott-insulator because of the very abrupt physical property switching during its semiconductor-to-metal transition (SMT) around 341 K (68 °C). In this work, through novel oxide-metal nanocomposite designs (i.e., Au:VO₂ and Pt:VO₂), a very broad range of SMT temperature tuning from ≈323.5 to ≈366.7 K has been achieved by varying the metallic secondary phase in the nanocomposites (i.e., Au:VO₂ and Pt:VO₂ thin films, respectively). More surprisingly, the SMT T_c can be further lowered to ≈301.8 K (near room temperature) by reducing the Au particle size from 11.7 to 1.7 nm. All the VO₂ nanocomposite thin films maintain superior phase transition performance, i.e., large transition amplitude, very sharp transition, and narrow width of thermal hysteresis. Correspondingly, a twofold variation of the complex dielectric function has been demonstrated in these metal-VO₂ nanocomposites. The wide range physical property tuning is attributed to the band structure reconstruction at the metal-VO₂ phase boundaries. This demonstration paved a novel approach for tuning the phase transition property of Mott-insulating materials to near room temperature transition, which is important for sensors, electrical switches, smart windows, and actuators.