Atomic Layer Deposition of Ultrathin Crystalline Epitaxial Films of V2O5.

Ultrathin epitaxial films (10-90 nm thick) of V2O5 have been grown on c-Al2O3 by atomic layer deposition using vanadyl acetylacetonate as the vanadium precursor along with oxygen plasma. Various process parameters have been optimized for the purpose, and excellent crystalline films could be obtained below 200 °C, without the need for post-heat treatment. With a moderate temperature window, the process yields a growth rate of 0.45 Å/cycle. The films have been characterized by electron microscopy, atomic force microscopy, Raman spectroscopy, and other means. The films exhibit a (001) preferred orientation with respect to c-Al2O3 and undergo compressive strain at the initial few monolayer growth to adjust epitaxially with the substrate. Heterojunction diodes based on TiO2(p)-(n)V2O5 as well as a humidity sensor have been fabricated using the V2O5 films.