Influence of ion beam irradiation on crystallographic structure and surface morphology of aluminium nitride thin films

Abstract

Aluminum nitride (AlN) thin films have been synthesised by ion beam assisted deposition method, and the influence of ion beam irradiation on microstructure and surface morphology has been studied by thin film X-ray diffraction (TFXRD) and by atomic force microscopy (AFM). In order to elucidate the influence of ion beam irradiation on the crystallographic structure, 10 nm thick c-axis oriented films synthesised with the ion beam energy of 0.05 keV are irradiated with nitrogen ions of 0.5 keV (no aluminum evaporation) after deposition for the same period as the deposition time and this process is repeated until the film grows to 200 nm in thickness. The TFXRD results reveal that the “piled up” films do not show the oriented structure, but are disordered to the multi-oriented state. AFM observations reveal that (1) the films synthesised with the nitrogen ion beam of 0.05 keV show the extreme smooth surface and the surface roughness increases with increasing the nitrogen ion beam energy and (2) the film surface synthesised with the ion beam energy of 0.05 keV does not change drastically by 2-keV ion beam irradiation after deposition. These results show that synthesis with high energy ion beam makes AlN films disordered structure and rough surface.