Thickness dependence of electrical and optical properties of sputtered Nickel oxide films

Nickel oxide thin films of various thickness were deposited by radio-frequency (RF) magnetron sputtering process in a pure oxygen atmosphere at RF power 200 W on unheated and heated for (400 °C) substrates. Sheet resistance and resistivity were measured using four probe and Hall effects. The results show that the lowest sheet resistance (16.87 kΩ/□) and resistivity (0.69 Ω cm) could be obtained on 200-nm thick samples prepared on unheated substrates. The transmittance of films decreased as the thickness of films increased. Crystalline properties of NiO films as a function of film thickness were investigated using X-ray diffraction. The preferred orientation of NiO film prepared on unheated substrates is (111). It becomes (200) when the substrate temperature was 400 °C. For similar film thickness, unheated substrates resulted in films with larger grain size than one obtained on substrates heated at 400 °C.