Sensing characteristics of epitaxially-grown tin oxide gas sensor on sapphire substrate

Epitaxial SnO2 film was grown on a sapphire substrate using a reactive rf magnetron sputter. The microstructure of the thin film was investigated using the 3C(2) beam line from a Pohang Light Source (PLS) consisting of a 2 GeV electron accelerator, four circle X-ray diffractometer, atomic force microscopy (AFM), and transmission electron microscopy (TEM) comparing with the SnO2 film on the polished alumina. It was confirmed that the thin film grew epitaxially on the sapphire substrate with a variant crystal structure [Development of microstructure controlled and ultrathin SnO2 gas sensing film, in: Proceedings of the 5th International Meeting on Chemical Sensors, Rome. Italy, 1994]. No grain boundary was exhibited on the surface of the epitaxial thin film. A large portion of the sorption sites in SnO2 films appears to react easily with the gas. An epitaxial SnO2 gas sensor, with a Pt heater and electrodes, exhibited a high sensitivity to combustible gases and a particular sensitivity of 95% to alcohol at 2000 ppm and 350 degreesC. The sensor also showed a good stability with small baseline drift and fast reaction and recovery times of about 5 and 30 s, respectively. This experiment confirms the good gas-sensing characteristics of an epitaxially-grown SnO2 gas sensor. (C) 2001 Elsevier Science B.V. All rights reserved.