Highly selective H2S sensor realized via the facile synthesis of N-doped ZnO nanocrystalline films

Material and synthesis compatibilities are more crucial to realize integrated sensor systems (lab-on-chip). Zinc oxide (ZnO) is a prospective material for gas-sensing applications because of its remarkable electrical and physical properties, non-toxic nature, and particularly its compatibility with silicon fabrication technology. In this communication, we present the results on the enhanced H2S response of nitrogen-doped ZnO (NZO) thin films achieved by controlling the Ar:N2 ratio during the RF sputtering process. All the films showed vertically oriented nanograins with high crystallinity. XPS studies indicated myriad adsorbed oxygen species for NZO films. Maximum response (S) for H2S, calculated from the ratio of sensor conductivity after and prior to gas exposure, was obtained at an operating temperature of 300 °C for the films deposited with Ar:N2 ratio of 2:1 (S = 45 for 5 ppm of H2S). Excess donor defects aided with the large adsorption energy due to nitrogen incorporation conceivably resulted in the enhanced response of NZO for H2S.