Studies on structural and optical properties of pulsed laser deposited NiO thin films under varying deposition parameters

Lattice parameter of NiO layers deposited using pulsed laser deposition is determined accurately using three parallel Bragg reflections. A small decrease in out of plane lattice parameter is found as O2 partial pressure is increased, which is attributed to the lattice contraction due to Ni vacancies. The NiO layers are found to be oriented along (111) direction on (0001) oriented Al2O3 substrate. The presence of Pendellosung oscillations indicates high crystalline and interfacial qualities of NiO layers, which gradually degrade with increase in O2 partial pressure. The NiO layer thickness determined from both x-ray diffraction and x-ray reflectivity show similar trend with O2 partial pressure. The optical band gap does not vary much due to the presence of very small compressive strain.