Nanostructured diluted magnetic semiconductor fabrication of Cu doped ZnO thin films by pulsed laser deposition (PLD).
Xu, Jeanie Weilin.
Date of Issue2009
School of Materials Science and Engineering
Future technology envisages the combination of magnetism and semiconductivity, known as spintronics. Such materials are called Diluted Magnetic Semiconductor (DMSs), where transition metals are doped in ZnO. Although DMSs have been extensively studied, reports are still contradicting without a definite conclusion. Past researches conclude that the inconsistency could be due to sensitive dependence of thin film on various conditions like target and substrate qualities, growth temperature and ambient pressure. The epitaxial growth and properties of the (ZnO)1−x(CuO)x thin films, where (x =0.01 - 0.07) was studied in this project. The films were grown on silicon substrates using Pulsed Laser Deposition (PLD). The influence of Cu doping on the thin films were studied. Further investigations on the effect of heat treatment on the magnetic properties of the films were done. The samples were annealed in argon atmosphere for 2 hours at 150°C, 200°C, 300°C and 400°C. Bulk pellets were prepared by conventional solid state method. The morphological, structural and magnetic properties of (ZnO)1−x(CuO)x DMS were characterized by Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), Surface Profiler, X-Ray Diffraction (XRD) and Vibrating Sample Magnetometer (VSM). The surface morphology of the films was uniformly decorated with isolated irregular-shaped nanoparticles. The Cu concentration in the as-deposited thin films was found to be slightly higher than that of target despite PLD’s high stoichiometry deposition. This could be attributed to the inhomogeneity of target material. XRD results confirm the presence of wurtzite ZnO and CuO in the (101) direction for target, whereas amorphous thin films were obtained before and after annealing. Room Temperature Ferromagnetism was observed in all the thin films. Hence, annealing does improve the magnetic moment significantly.
Final Year Project (FYP)
Nanyang Technological University