Ellipsometric study of optical properties of Sm-doped ZnO thin films Co-deposited by RF-Magnetron sputtering

Non-volatile, rewritable and ultra-high-density optical memory necessitates photoreduction of valence state change of rare Earth elements. However, the sensitization of a nanoscale ultra-high storage medium possessing high optical transmission is a challenge. Herein, we studied the optical properties of Sm deposited in ZnO thin film by Radio Frequency (RF) sputtering deposition method. The Sm3+ content, optical properties, and crystal structure were investigated via X-ray fluorescence (XRF), variable angle spectroscopic ellipsometry (VASE) and X-ray diffraction (XRD), respectively. X-Ray fluorescence (XRF) upheld the presence of Sm grains and verified its percentage increase with the deposition power. VASE data were fitted using effective medium approximation method (EMA) to determine the Sm3+ volume fraction and mass thickness (MT). XRD study verified the Wurtzite hexagonal structure stability of ZnO and no crystal structure or phase distortion occurred. The band energy gap of the composite decreased with Sm: ZnO content. The roughness and thickness uniformity of the thin films were determined by the VASE study and were confirmed using field emission scanning electron microscopy (FESEM) and atomic force microscope (AFM). The optimum Sm ions content of high transmittance has been determined.