Enhancement in CO gas sensing properties of hydroxyapatite thick films: Effect of swift heavy ion irradiation

This paper investigates the effect of swift heavy ion (SHI) irradiation on surface morphology of Hydroxyapatite (HAp) thick films and modification in gas sensing characteristics. The HAp nanopowder is synthesized by wet chemical process and the thick films are prepared by screen printing technique. These films are irradiated with Ag⁷⁺ ions with energy of 100 MeV at different fluences ranging from 3 × 10¹⁰ to 3 × 10¹³ ions/cm². X-ray diffraction and atomic force microscopy tools are employed to examine the phase and surface modification in HAp thick films due to swift heavy ion irradiation. The ion irradiation study shows that crystallinity decreases and grain size changes with increase in ion fluence. A precise study on gas sensing is carried out to confirm operating temperature of HAp thick film sensor to detect CO gas. Saturation region of the film with increasing gas concentration and other parameters such as response and recovery time are also investigated from the point of view of using HAp films as a sensor device. SHI irradiated HAp thick film shows enhancement in the gas response and saturation limit for CO gas. Furthermore, the irradiated HAp film shows fast response and recovery time for CO gas. The study concludes that nanoceramic HAp thick film is an excellent CO gas sensor at an operating temperature of 195 °C.