Reactive magnetron sputtered AlN thin films: structural, linear and nonlinear optical characteristics

This study investigates the structural and optical characteristics of aluminum nitride (AlN) thin films deposited using reactive magnetron sputtering (dcMS)in an Ar + N₂ (80:20%) atmosphere. The AlN thin films were deposited on a substrate without any heat treatment process, and their structural properties were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The optical properties of the AlN thin films were studied by analyzing their transmittance and reflection using a double-beam UV–Vis–NIR spectrophotometer within the 300–1000 nm range. The results show that the AlN thin films have a wurtzite structure with a preferred orientation, and the average particle size is in the range of 80–83 nm. The AlN thin films have an average transmittance of approximately 70% and are transparent in the visible spectrum. The direct bandgap increases from 3.70 to 3.98 eV with increasing work pressure, and the refractive index increases to 2.17. Moreover, nonlinear optical parameters, including the nonlinear refractive index n₂ and the nonlinear absorption coefficient β_c, were calculated for the AlN thin films. The unique characteristics described above suggest potential applications that could make use of these properties.