Gas sensing properties in epitaxial SnO2 films grown on TiO2 single crystals with various orientations

Epitaxial SnO2 films were deposited on TiO2 single crystals with various orientations by plasma enhanced atomic layer deposition (PEALD), and their structural characteristics and gas sensing properties were investigated, particularly focusing on the crystallographic orientation dependence of H2 gas response. Dibutyltindiacetate (DBTDA) was used as Sn source, and (1 0 0), (0 0 1), (1 1 0), and (1 0 1) TiO2 were employed as substrates for SnO2 deposition. All the SnO2 films were ∼90 nm thick after 1000 ALD cycles and epitaxially grown on TiO2 substrates, which were confirmed by X-ray pole figure and high resolution transmission electron microscopy (HRTEM). Differently oriented epitaxial SnO2 films showed the different H2 gas response and different temperature dependence of gas response. The (1 0 1) SnO2 films grown on (1 0 1) TiO2 exhibited the highest H2 gas response of ∼380 toward 1000 ppm H2/air at 400 °C, which was associated with the different temperature dependence of resistance in (1 0 1) film rather than the microstructural characteristics and chemical composition compared to the other films.