Surface modified hydroxyapatite thick films for CO2 gas sensing application: Effect of swift heavy ion irradiation

Swift heavy ion irradiation (SHI) is used to modify the structural and gas sensing properties of Hydroxyapatite (HAp) thick films. The HAp thick films, prepared by screen printing technique, are irradiated with a variable fluence (3×1010 to 3×1013 ions/cm2) of Ag7+ ions of 100 MeV energy. XRD shows gradual change in crystallinity of the matrix with increase in ion fluence. Atomic force microscopy reveals the agglomeration of grains with pronounced cluster type structure at relatively higher ion fluence. For confirmation of efficient gas sensing of pristine and irradiated HAp thick films, repeatability and reproducibility tests are conducted in a carbon dioxide atmosphere. The parameters responsible for device applications such as, gas uptake capacity, response to test gas and recovery time of HAp film sensor are also investigated. SHI modified HAp films show the maximum enhancement in the gas response and also in increased gas uptake capacity for the fluence 3×1011 ions/cm2. Moreover, SHI has resulted in modification of gas response and recovery time for CO2 gas. The remarkable observation is to note that SHI irradiation improves the sensor characteristics of the HAp films without affecting the working temperature (165 °C) of gas sensor.