Preparation And Performance Study Of Transition Metal Doped ZnO Thin Films

ZnO is a wide band-gap semiconductor material. The room temperature ferromagnetism of ZnO films can be acheived by doping with transition metals (TM), and on some degree, growth orientation of the doped ZnO films were changed. The results offer an opportunity for preparation of non-polar ZnO thin films. ZnO based diluted magnetic semiconductors have extensively potential applications in spintronics and photoelectron areas, while the investigation of non-polar ZnO can enhance the luminous efficiency of ZnO based devices.In this paper, Fe-doped and Fe-Ga co-doped ZnO diluted magnetic semiconductor thin films grown on quartz substrate by RF-magnetron sputtering are studied; the structure and properties of ZnCoO and ZnMnO films prepared by pulsed laser deposition (PLD) are investigated. The main results are obtained as follows:1. Rapid annealing enhanced the ferromagnetism (FM) of Fe-doped ZnO films grown in Ar/O2. All the films grown in Ar are n-type and the carrier concentration could increase when Ga is doped. The state of Fe in the films was investigated exhibiting Fe3+. Magnetic measurements revealed that room temperature ferromagnetism in the films were doping concentration dependent and would enhance with Ga doping. The origin of the observed FM is interpreted by the overlapping of polarons mediated through oxygen vacancy based on bound magnetic polaron model.2. The structural, electrical, optical, and magnetic properties of the as-prepared films were investigated. It is uncovered that the preferred orientation of ZnCoO thin film gradually transits from along (002) plane to along (101) plane through Ga doping. Moreover, the Zn(Co,Ga)O thin film deposited on glass substrate has nearly a single (101) peak, which is proposed be associated with the surface energy difference between ZnCoO (002) and ZnCoO (101) when Ga was doped. Additionally, compared to ZnCoO, it is found that the Zn(Co,Ga)O thin film has better electrical and magnetic properties, and with a larger optical band gap.3. Zn(Mn,Li)O and Zn(Mn,Na)O films exhibited relatively well crystallinity. The growth orientation of the films depends on deposition temperature and pressure. Moreover, the magnetic properties are related to growth orientation, which is proposed be associated with the different defects of the different oriented films.