Preparation Of Zno-based Diluted Magnetic Semiconductors And Magnetic Study

Much of the attention on diluted magnetic semiconductor (DMS) materials is due to its potential application in what is now called"spintronics"devices, which exploit spin in magnetic materials along with charge of electrons in semiconductors. Due to the incorporation of magnetic ions, DMS exhibit some novel properties as compared to conventional semiconductors.The research on diluted magnetic semiconductors is one of the frontiers of modern physics. As one of the most promising DMS candidates, transition metals doped ZnO has been receiving great attention very recently. Although there have been many inspiring results in both theoretic and experimental fields, some questions are still to be further solved, such as the origin of the observed ferromagnetism, the lower transition temperature and so on. Therefore, in this work, our attention has been centralized on ZnO based DMS.1. The Zn0.96Mn0.04O powder and thin films were prepared by the solid-state reaction processes and radio-frequency (RF) magnetron sputtering. No indication of a secondary phase was found in either sample. All the samples were single phase and had hexagonal wurtzite structure. The magnetic properties indicated that the powder was paramagnetic down to temperatures of 3 K, while the thin films annealed in vacuum were ferromagnetic at room temperature with a transition temperature of about 400 K. The largest saturated magnetization (Ms) was found to be about 1.05μB/ Mn, while the coercive force was found to be 100 Oe. Based on the various analyses, ferromagnetism in thin films is likely to be an intrinsic property of the lattice. Additionally, the crucial factors resulting in ferromagnetism in DMSs are growth conditions and defects.2. A series of Cu-doped ZnO films was prepared using direct current reactive magnetron sputtering. The Hall Effect measurements indicated that all the films were n-type semiconductors. Magnetic measurements indicated that all the films were ferromagnetic at room temperature and the moment per Cu ion decreased with increasing copper concentration and nitrogen doping. The transition temperature was also decreased due to nitrogen doping. The resistivity increased with increasing copper concentration and nitrogen doping. Based on the careful analyses, it can be concluded that ferromagnetism in thin films is likely to be an intrinsic property of the lattice and itinerant electrons play an important role in ferromagnetism.3. All the nitrogen-doped Zn0.93Co0.07O thin films deposited on the glass substrates were prepared by magnetron sputtering, which have shown ferromagnetic property at or above room temperature. With the ratio of N2 to Ar increase, the carrier type transited from electron to hole and p-type Zn0.93Co0.07O films were obtained. The moment per Co ion decreased with nitrogen density increase and the Curie temperature increased remarkably with nitrogen doping. The electron-mediated ferromagnetic interaction mechanism can be used to explain the change of magnetic moment, while it can't explain the trend of transition temperature. Such results give a further understand of Co-doped ZnO, meanwhile, the origin of ferromagnetism needs to be explored.