Low-Temperature Epitaxy of Perovskite WO3 Thin Films under Atmospheric Conditions

Abstract

As Si electronics hits fundamental performance limits, oxide integration emerges as a solution to augment the next generation of electronic and optical devices. Specifically, oxide perovskites provide diverse functionalities with a potential to create, tune, and combine emergent phenomena at interfaces. High-level crystalline order is needed to realize these functionalities, often achieved through epitaxy. However, large-scale implementation in consumer devices faces challenges due to the need for high-temperature deposition in complex vacuum systems. Herein, this challenge is addressed using atmospheric pressure spatial chemical vapor deposition, a thin-film fabrication technique that can rapidly produce uniform films at sub-400 °C temperatures under atmospheric conditions over ≈cm2 areas. Thus, the deposition of epitaxial perovskite tungsten trioxide, WO3, thin films is demonstrated at a rate of 5 nm min−2 on single-crystal substrates at 350 °C in open-air conditions enabling a high-throughput process. The resulting films exhibit crystallographic and electronic properties comparable to vacuum-based growth above 500 °C. The high-quality epitaxy is attributed to the energetics of the exothermic decomposition reaction of the W[CO]6 precursors combined with the stabilization of a hot zone near the substrate surface. From this work, the way can be paved for low-temperature atmospheric-pressure epitaxy of a wide range of other perovskite thin films.