Structural and optical properties of ZnO co-doped with Co and Ni thin films deposited by pulse laser deposition technique

Thin films of Zn0.9 Co0.1−xNixO (x = 0.0, 0.02, 0.04, 0.06, 0.08, 0.1) series were deposited by Pulsed Laser deposition technique (PLD) on a single crystal (100) silicon substrate. The structure of the films was confirmed as single phase hexagonal wurtzite structure by X-ray diffraction technique (XRD). The highest intensity peak was found at (002) plane. The surface morphology of thin films studied by Scanning Electron Microscope (SEM) depicted the high grain growth with definite boundaries. The room temperature resistivity measurements were carried out by four-point Probe methods which showed the semiconducting behavior of the thin films. Magnetic properties characterized by Vibrating Sample Magnetometer (VSM) at room temperature, exhibited the weak ferromagnetic or superparamagnetic behavior due to the alignment of the spins in the same direction around the oxygen vacancy and Co/Ni ions. Optical properties were observed by Spectroscopic Ellipsometry. The thickness of the films lied in 200-265 nm range and the bandgap energy was found to decrease from 3.09 to 3.03 eV confirming the inclusion of Ni a deep level impurity.