Deposition and properties of ZnSiO3-containing zinc oxide thin films reactively sputtered at room temperature
Résumé
Zinc oxide thin films were deposited on glass substrates using reactive radio-frequency sputtering at room temperature over a range of radio-frequency powers (from 100 to 250 W). The morphological, structural and optical properties of the deposited thin films were investigated using X-ray diffraction, optical transmission measurements, scanning electron microscopy, and photoluminescence measurements. All the as-grown thin films consist of hexagonal ZnO, and a crystalline ZnSiO3 phase for several radio-frequency powers. The post-annealing in air at 550 °C results in the deterioration of the ZnSiO3 phase and an improvement in the ZnO crystallinity of the samples, with a crystallite size ranging from 20 to 30 nm. The clustering of the post-annealed sample is promoted by a critical amount of ZnSiO3 in the as-grown samples. Optical transmission and photoluminescence analyses revealed the bandgap and the energy transitions in the deposited ZnO. As-grown thin films exhibit a direct bandgap of 3.29 eV. Crystalline ZnSiO3 was found to enable a direct transition with an energy of 2.87 eV at room temperature.