Preparation And Properties Of ZnO-based Diluted Magnetic Semiconductors

With the decrease of the size of traditional integrated circuit device, various quantum effects of electronic will become more prominent, among which electronic spin properties take a very important place. In spintronics, to make the spintronic devices available, the injection of spin must be highly effective. Diluted magnetic semiconductors have the properties of both semiconductors and magnetic materials, and spin injection can be effectively carried out by them. The properties of zinc oxide based diluted magnetic semiconductor were studied from the theoretical and experimental aspects.The theory study was carried out by first-principles calculations. The two main intrinsic defects of ZnO, VO and Zni, and Lii and LiZn formed by Li doping were studied. The results show that any of the above-mentioned defects are not able to induce ferromagnetism in ZnO. Secondly, Mn or Ni single doped ZnO was also simulated. In Mn-doped ZnO, Mn atoms tend to come close and the spins of Mn atoms tend to be antialigned. So the Mn atoms tend to form antiferromagnetic clusters. It shows that Mn single doped ZnO is difficult to form a diluted magnetic semiconductor with room temperature ferromagnetic. In the Ni-doped ZnO, the Ni spin arrangements have little effect on the energy of the system. So Ni single doped ZnO may have ferromagnetism.The experiment study was carried out by traditional solid-state reaction method. The Ni single doped, Li and Ni co-doped and Mn and Ni co-doped ZnO based diluted magnetic semiconductors were prepared. Room temperature ferromagnetism can be found in any of the three kinds of materials. When the concentration of magnetic ion doped is less than 5 mol %, the magnetization under the same magnetic field will increase with the concentration of the magnetic ion. However, the magnetism of NiZnO material will turn from non-ferromagnetism to ferromagnetism when it doped with small amounts of Li, and when Li concentration is high, the ferromagnetic come back. In MnZnO sample, the excessive Li could weaken the ferromagnetic of the system. ZnO-based DMS ferromagnetism may originate from the carrier mediated exchange interaction and the carrier concentration of ZnO might change when Li doped.