Beyond single domain sensing: Adapting indium tin oxide thin film crystallinity for enhanced optical and electrochemical performance

Indium tin oxide (ITO) films are commonly applied as transparent electrodes for optoelectronic devices. However, when their optical and electrochemical sensing applications are considered, at best, simultaneous, it is challenging due to contradictory material properties expected in these domains. In this work, we explore the capability to enhance dual-domain performance by tailoring the crystalline properties of ITO thin films when lossy-mode resonance (LMR) and cyclic voltammetry are considered as optical and electrochemical approaches, respectively. First, sputtered amorphous ITO films were processed via controlled thermal annealing, and its impact on crystallite size, charge carrier density, and mobility, as well as optical and electrochemical properties, has been investigated. Our findings reveal that high electron concentration and enhanced mobility, driven by larger crystallites, significantly improve the electrochemical performance, but also significantly change the optical properties. Despite the inherent trade-offs between the optical and electrochemical properties, here we propose a strategy for optimizing properties in both domains, enabling high-sensitivity label-free dual-domain sensing and biosensing.