Optimizing deposition regimes to fabricate VO 2 /TiO 2 /c-Al 2 O 3 thin films for active metasurfaces

Decreasing the scale of vanadium dioxide (VO 2 ) structures is one of the ways to enhance the switching speed of the material. We study the properties of VO 2 films of altered thicknesses in the range of 20–170[Formula: see text]nm prepared on c-sapphire substrates with a TiO 2 sublayer by pulsed laser deposition (PLD) method. The synthesis regime to design a TiO 2 film was preliminarily optimized based on XRD data. XRD patterns reveal an epitaxial growth of the VO 2 films with distortion of the monoclinic cell to hexagonal symmetry. The positions of the lattice vibration modes in Raman spectra are similar to those in bulk VO 2 when the film thickness is greater than [Formula: see text][Formula: see text]nm. For VO 2 films thicker that [Formula: see text][Formula: see text]nm, a lattice strain results in the modes’ positions and intensity change. However, the electrically triggered transition in a [Formula: see text][Formula: see text]nm thick VO 2 film reveals forward and reverse switching times as short as 20[Formula: see text]ns and 400[Formula: see text]ns, correspondingly.