SnO2 Tailored by CuO for Improved CH4 Sensing at Low Temperature

Trace level methane (CH4) detection is demonstrated at low temperature. Functional metal oxide of SnO2 tailored by CuO is prepared via a co-precipitation chemical route followed by annealing in air. Raman spectroscopy confirms presence of A(g) mode of CuO at 290cm(-1) along with A(1g) mode of SnO2 at 630cm(-1). Results from the X-ray diffraction and transmission electron microscope indicate that both crystalline SnO2 and CuO are present in the composite. Particle size of SnO2 is found to be larger in the composite than the pristine-annealed SnO2 of 25nm at 800 degrees C. However, sensor studies with CH4 reveal stronger response and low operational temperature of 100 degrees C for the composite in comparison to the pristine-annealed SnO2 which shows poor response (< 1%) even at higher temperature of 150 degrees C. Current-voltage measurements support the formation of local p-n junctions in the CuO-SnO2 composite. The role of n-p junction in the composite is elaborated and correlated to the improved response.