Combinatorial synthesis of non-stoichiometric SiOx thin films via high-throughput reactive sputtering

Oxygen vacancy defects have been widely studied for fundamental research and industrial applications, because they significantly influence the physical properties of oxides. Precise and systematic control over oxygen deficiency is a prerequisite for qualitative and quantitative studies on the effect of oxygen defects. In this paper, we report a novel approach to accurately control the oxygen deficiency of oxide thin films using high-throughput reactive sputtering (HTRS). SiOx combinatorial libraries consisting of 110 × 130 cells (cell area of 1 cm2) were fabricated on a large-scale glass substrate (110 × 130 cm2). These libraries allow for macroscopic analysis tools that are not amenable to the existing combinatorial methods, such as optical and x-ray spectroscopies. The cells exhibit spatial gradients in optical constants and optical transmission depending on the oxygen deficiency, indicating a gradual transition from Si to SiO2. X-ray photoelectron spectroscopy analysis reveals that the libraries consisting of silicon oxides with diverse oxidation states are in good accordance with the continuous compositional variation. The HTRS method demonstrates the controllability of oxygen deficiency by 0.5% (Δδ ≈ 0.01) and provides potential controllability of 0.05% (Δδ ≈ 0.001). Our approach provides the systematic control of oxygen deficiency and makes a step toward discovering the emerging properties of non-stoichiometric oxides.