Structural and Optical Characterization of Dual Phased AlScN Thin Film Co-Sputtered on Sapphire

Abstract

Abstract In the present report, the structural and optical characteristics of RF sputtered Al52Sc48N (ASN) was studied with X-ray diffraction (XRD), Raman spectroscopy and UV-Vis reflection spectroscopy. XRD spectra shows three distinct peaks at 35.31˚, 40.80˚ and 59.32˚ of which two of them belong to cubic phase while one of them suggest a hexagonal structure. The Raman spectra show some unusual broadening of the peaks with a huge redshift. The addition of Sc has induced a great amount of strain in ASN which is reflected in the redshift of Raman peaks, smaller grain size calculated by Scherrer equation and micro cracks observed in FESEM images. The reflectivity spectra show interference fringe pattern at higher wavelength with the pattern diminishing gradually as the bandgap threshold approaches. An abrupt drop in reflection around 254 nm is observed which is believed to be of Surface Plasmon Resonance of Al. The refractive index was calculated using envelope method and it shows a typical inverse behaviour with respect to the wavelength. The thickness of the film as calculated by cross sectional SEM image is almost similar to that calculated using envelope method of UV-Vis reflection spectra.