Preparation and characterization of NiO thin films for gas sensor applications

Abstract

Nickel oxide (NiO) thin films were prepared by DC reactive magnetron sputtering from a nickel metal target in an Ar+O 2 mixed atmosphere in two sputtering modes. The oxygen content in the gas mixture varied from 15 to 45%. The films deposited in the metal-sputtering mode at a high target voltage (320–326 V) resulted in a polycrystalline (fcc) NiO phase with nearly stoichiometric composition. On the contrary, the films prepared in the oxide-sputtering mode at a low target voltage (293–298 V) were amorphous and oxygen rich. All examined NiO films were semiconductors and their conductance increased by four orders of magnitude between 25 and 350°C. Finally, NiO films were tested in order to investigate their response to NH 3 at various operating temperatures.