Scalable Single-Step Open-Air Combinatorial Growth of Multifunctional Metal Oxide Thin Films by Spatial Atomic Layer Deposition

Abstract

Compositionally graded metal oxide thin films enable rapid exploration of structure–property relationships, yet their fabrication typically relies on vacuum-based, multistep processes. Here, we present an atmospheric-pressure spatial atomic layer approach that enables the single-step, open-air synthesis of zinc–tin–oxide (ZTO) thin films with lateral compositional gradients over 3-in. wafer-scale substrates. A custom reactor head with spatially tailored precursor delivery generates continuous and reproducible composition gradients in under 1 h without vacuum processing or sequential depositions. Comprehensive structural, morphological, optical, and compositional characterization confirms smooth lateral variations in ZTO film composition and crystallinity, with Sn/Zn atomic ratios spanning approximately 0.4–0.8 across one of the films, forming unique material libraries in a single open-air deposition step. As a proof of concept, the graded ZTO films are integrated into chemiresistive sensor arrays comprising 20 compositionally distinct sensing columns on a single wafer, exhibiting composition- and temperature-dependent (at 200 °C) responses to volatile organic compounds within a single device platform. Additionally, electrical measurements performed across the gradient show unique current–voltage properties at each composition, alluding to multi-usage in electronic applications within the same chip. This work establishes a scalable and cost-effective strategy for rapid fabrication of oxide material libraries and wafer-scale collective device assemblies under ambient conditions.