Development of Agile Titania Sensors Via High- Temperature Reductive Etching Process (HiTREP): I. Structural Reorganization

High selectivity, enhanced sensitivity, short response times and long shelf-life are much sought-after features in solid-state chemical sensors for the detection and metering of gas(es) of interest. Because the sensing mechanism of semiconducting oxides is invariably surface dominated, benign microscopic features are desirable to realize a useful sensing material. In principle, such morphological features could be incorporated in a number of semiconducting oxides by employing a technique based on thermodynamic consideration of the metal/metal oxide coexistence. By dynamically modulating the equilibrium oxygen partial pressure across the metal/metal oxide proximity line, renewed formulation and growth of an oxide surface on an atomic/submolecular level with exotic morphological features under conditions of oxygen ‘‘deprivation’’ or ‘‘enrichment’’ has been achieved practically in a number of potential ceramic sensor systems. In the case of oxides that are not amenable to such classical oxygen partial pressure modulation, a novel high-temperature reductive etching process (HiTREP) could be exploited to recreate the smart nanofeatures to impart the desired accentuation effect. This surface modification method was applied to a new commercially available aqueous plasma electro-deposited (PED) titania thick film, and the microscopic results of this strategy are presented.