Structural characterization of AlN thin films grown on sapphire by atomic layer deposition

Abstract

In this article, two sets of AlN thin films were produced on sapphire wafers with diverse surface orientations (C-, M-, R-, and A-) via atomic layer deposition. Various material characterization techniques were applied to investigate the morphological, structural, and optical properties of the AlN films, including atomic force microscope (AFM), X-ray diffraction, Raman scattering, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible spectrophotometer (UV–vis). The AFM results reveal that all AlN films are uniformly covered on the sapphire substrate, with no pinholes or cracks. Raman scattering spectroscopy indicates that the AlN thin films deposited on A-plane and M-plane sapphire substrates have low defect concentration. According to XPS results, the surface chemical state and element ratios of the AlN films produced on sapphire substrates with varied surface orientations are constant. The results of UV–vis transmission measurements show that the AlN film on M-plane sapphire substrate has the highest transmittance.