Effect of Additives of Pt, Pd, Ag, and Y in Thin Nanocrystalline SnO2 Films on the Characteristics of Resistive Hydrogen Sensors

Abstract

The results of studying electrical and gas sensitive characteristics of H₂ sensors based on thin nanocrystalline SnO₂ films with the Pt, Pd, and Ag dispersed layers deposited on the surface and Ag, Y, and Ag + Y additives in the volume are presented. It is shown that various combinations of catalysts on the surface and in the volume have a significant effect on the microstructure of films and density of oxygen adsorption sites on the surface of tin dioxide. As a result, the resistance values of sensors in clean air R₀, activation energies of the temperature dependences of R₀, responses to hydrogen in the concentration range of 50–2000 ppm are different. Studies performed by the method of UV-visible spectroscopy revealed in the absorption spectra of films with a silver addition in the volume a band of surface plasmon resonance of silver indicating that the additive is present in the form of metallic Ag nanoparticles. Particular attention was paid to the influence of long-term tests on the properties of sensors with the listed additives. It was established that the joint introduction of Ag+Y into the volume of films prevents the increase of the resistance and responses during prolonged exposure to hydrogen, which is observed during the operation of all other samples studied. Possible mechanisms for changing the sensors’ properties during testing and the role of additives in their stabilization are considered.