To tune down the phase transition temperature of VO2, doping technology was used.
In our experiments, high valence elements— tungsten from the source of ðNH4Þ10W12O41 _ 5H2O (Wako,Japan) was used for cation substitution.
For this purpose, the doped samples were fabricated by adding appropriate amount of dopants just before sealing the Teflon vessel and then followed by hydrothermal treatment.