Effect of thickness on physico-chemical properties of p-NiO (bunsenite) thin films prepared by the chemical spray pyrolysis (CSP) technique

P-type NiO thin films have been prepared by spray pyrolysis technique using nickel acetate Ni(CH3COO)2·4H2O as the starting precursor at 450 °C. NiO films were deposited with the aim of studying structural, phase evolution, optical, electrical and surface morphological property modifications with thickness. Prior to deposition, non-isothermal decomposition of nickel acetate tetrahydrate was studied using thermogravimetry and differential thermal analysis to get favorable temperature range for the formation of the title compound. Films were prepared for three different thicknesses in the μm range. Prepared films using 0.2 M precursor for the thickness 0.316 μm were amorphous while those deposited for the thickness 0.441 μm were single phase with polycrystalline cubic lattice (a = 4.194 Å). Broad absorption bands in the low wavenumber finger print region 820–400 cm−1 have been assigned to the bonding between Ni and O. From spectral transmittance measurements and using Swanepoel's equations, the optical constants have been evaluated over the entire wavelength range 250–1000 nm. NiO film with low resistivity (4.34 Ω cm) was achieved which has higher carrier concentration of 0.117 × 1024 m–3 with mobility in the order of 10−5 m2/V s. Atomic force microscopy measurements showed that the RMS surface roughness was 6.21 nm, which is the lowest reported value for the NiO films.