An investigation into the effect of thickness and annealing temperature on RF sputtered ZnO thin film properties for photonic applications

In this work, ZnO thin films were deposited on glass substrates by RF magnetron sputtering for 60 and 120 min, respectively. The as-grown films were annealed in air for one hour (1h) at various temperatures, ranging from 300... [ view full abstract ]

In this work, ZnO thin films were deposited on glass substrates by RF magnetron sputtering for 60 and 120 min, respectively. The as-grown films were annealed in air for one hour (1h) at various temperatures, ranging from 300 to 500 °C. Effects of film thickness and post-annealing on the structural, morphological, optical and waveguiding properties were investigated. X-ray diffraction (XRD) analyses showed that all ZnO films have a hexagonal wurtzite structure with higher c-axis preferred orientation, better crystallinity, larger crystallite size and lower compressive stress as film thickness and annealing temperature increase. Scanning electron microscopy (SEM) micrographs and atomic force microscopy (AFM) images revealed that the morphology and surface roughness of the ZnO samples depend on the film thickness and heat treatment temperature. The UV-Vis spectrophotometry characterization indicated that annealing enhanced the optical quality of the film regardless of the film thickness. M-lines spectroscopy (MLS) measurements at 632.8 nm wavelength put into evidence that the as-grown ZnO planar waveguides support single and multi-well confined guided modes for both transverse electric (TE) and transverse magnetic (TM) polarizations.