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

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. The integration of oxide electronics in the mainstream technology still faces challenges associated with manufacturing processes at high temperatures and under vacuum. Deposition of epitaxial perovskite WO3 films is demonstrated at low temperatures and in open air using atmospheric pressure spatial chemical vapour deposition. Epitaxy is achieved through an exothermic reaction of the precursor with O2, stabilizing a hot zone near the substrate.