Fabrication and characterization of Co, Al:ZnO thin films by a sol-gel spin coating technique for ferromagnetic applications

Transparent polycrystalline ZnO and Co,Al co-doped ZnO [Zn_1-x-yCo_xAl_yO; x = 0.03; y = 0.02] thin films were fabricated using sol-gel spin coating on glass substrates and subsequently annealed at 500 °C for 2 h in an ambient atmosphere. The decomposition of the precursors and formation of the metal oxide during annealing was explained by thermal analysis. X-ray crystal diffraction analysis on the co-doped ZnO thin films confirmed the formation of the hexagonal wurtzite structure. Microstructural studies revealed that the films were filled with particulates of sizes ranging between 40-50 nm and with a uniform film thickness of about 700 nm after annealing at 500 °C. Atomic force microscopy (AFM) images demonstrated a fine and smooth surface of the thin films. The spin coated films have also been shown to possess polycrystalline grains with a compact and void-free morphology. The energy dispersive X-ray spectroscopic (EDS) analysis confirmed the presence of Co, Al, Zn and O. The room temperature (300 K) ferromagnetic behavior of Co, Al co-doped ZnO thin films is also discussed.