Muraoka et al reported that the T C for epitaxial VO 2 films grown on TiO 2 (001) substrates was reduced to 26 ☌, while the T C increased up to 96 ☌ for VO 2 films grown on TiO 2 (110) substrates. Another approach to tune the T C of VO 2 films is to use epitaxial strain. However, increasing the doping level in VO 2 films generally leads to either a reduction in the magnitude of the transition or a broadening of the transition width.
Among them, introducing doping elements, such as W, Mo, Ti, and Mg, is a common approach due to the ability to shift the fermi level in semiconducting VO 2. Many efforts have been focused on tuning the T C of VO 2 films over the past decade. In order to use VO 2 thin films as a technologically relevant material, it is necessary for its T C to be tunable to fulfill specific working environments in various devices. Because of these unique properties, VO 2 has been exploited in various devices such as Mott field effect transistors, 6,7 6. Upon transitioning to the metallic phase, the electrical resistance decreases by four orders of magnitude and the optical transmittance in the near infrared decreases by as much as 60 %. and it can occur at ultrafast timescales (∼100fs). This semiconductor-to-metal transition (SMT) can be induced thermally, 2 2.
VO 2 has gained considerable interest due to its first-order phase transition between a low-temperature monoclinic phase (semiconducting state) and a high-temperature tetragonal phase (metallic state) at a transition temperature ( T C) ∼ 68 ☌.
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