Characterization of NiO thin films on α-Al2O3 before and after heat treatment

Abstract

The NiO-α-Al2O3 system is of interest as a model system for the study of phase boundaries and reaction kinetics in oxide ceramics. Such a system is of new importance when one of the constituents is a thin film because the reaction kinetics and its dependence on film microstructure is not well understood. Additionally, solid-state reactions between a thin film and single-crystal substrate can be used to produce buffer layers for heterojunctions.In the present study, thin films of NiO have been grown on single-crystal α-Al2O3 substrates by pulsed-laser ablation (PLA). The PLA system used a KrF (248nm) excimer laser operating at 350 mJ per pulse with a pulse repetition rate of 10 Hz. The laser beam was focused to a spot 1×2mm on the surface of rotating NiO pellet. Films were grown at nominal substrate temperatures of 750°C and oxygen pressures of about 10 mTorr. Films were grown both on bulk substrates for which 6000 laser pulses was used to produce 1000Å films and electron-transparent substrates for which 500 laser pulses was used to produce 80Å films.