Effect of oxidation temperature on the properties of NiOx layers for application in optical sensors

Abstract Thin NiOx layers were prepared by oxidation at 400, 500 and 600 °C of metallic Ni deposited by electron beam evaporation. The bandgap of NiOx determined from optical measurements increases from 3.6 to 3.7 eV with the increase of oxidation temperature from 400 to 500°C. Higher temperature leads to larger grain sizes, 12.6 nm at 400 °C, 15.3 nm at 500 °C and 16.1 nm 600 °C. Photodiodes based on NiOx/Si heterostructure were fabricated by evaporation of semitransparent Au top contacts. The structures with NiOx obtained at 500 °C showed superior diode characteristics compared to the other two types of devices with dark current