SnO­2 Tailored by CuO for Improved CH4 Sensing at Low Temperature

Trace level methane (CH 4 ) detection is demonstrated at low temperature. Functional metal oxide of SnO 2 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 290 cm −1 along with A 1g mode of SnO 2 at 630 cm −1 . Results from the X‐ray diffraction and transmission electron microscope indicate that both crystalline SnO 2 and CuO are present in the composite. Particle size of SnO 2 is found to be larger in the composite than the pristine‐annealed SnO 2 of 25 nm at 800 °C. However, sensor studies with CH 4 reveal stronger response and low operational temperature of 100 °C for the composite in comparison to the pristine‐annealed SnO 2 which shows poor response (<1%) even at higher temperature of 150 °C. Current–voltage measurements support the formation of local p–n junctions in the CuO–SnO 2 composite. The role of n–p junction in the composite is elaborated and correlated to the improved response.