Effect of Pt, Pd, Au additives on the surface and in the bulk of tin dioxide thin films on the electrical and gas-sensitive properties

The microstructure and properties of thin ($\sim$100 nm) SnO$_2$ films with noble metals Pt, Pd, Au additives, grown by dc magnetron deposition are studied. It is shown that the introduction of additives into the bulk and the deposition of dispersed catalysts on the semiconductor surface make it possible to control the sensor parameters in pure air and upon exposure to reduction (CO, H$_2$, CH$_4$) and oxidation (NO$_2$) gases. Possible mechanisms for the effect of Pt, Pd, Au on the bulk and surface properties of tin dioxide are discussed. The technological conditions for film growth, which provide the selective detection of low concentrations (10–100 ppm) of CO and H$_2$, below-explosive concentrations (0.5–2.5 vol%) of methane, and trace concentrations (0.05–5 ppm) of NO$_2$ are determined.