Epitaxial growth of W-doped VO2/V2O3 multilayer on α-Al2O3(110) by reactive magnetron sputtering

Multilayer epitaxy with a W–VO2 top layer over a bottom layer of which the crystal phase depends on the starting oxygen flow, was done on α-Al2O3(110) by reactively sputtering a V–W (1.6 at.% wt.) alloy target at linearly increasing oxygen flow without interrupting film growth. For the film deposited in the oxygen flow from 10 to 26 sccm, a W–VO2/W–V2O3 multilayer was formed on α-Al2O3(110) with the epitaxial relationship being (001)f // (110)s, (110)f // (001)s for W–V2O3, and (010)f // (110)s, (100)f // (001)s for W–VO2 where f and s denote the film and substrate, respectively. The formation of a triple domain structure was confirmed in the W–VO2 top layer due to the strong influence from the symmetry of the substrate. The multilayer shows phase transition behavior differing from the single layer film, which was presumably due to the effects of W-doping, compositional gradient, and strain.