The Study On The Structure And Properties Of Fe And Cr Doped ZnO Films

ZnO is a directed band semiconductor with a big binding energy. It has gained substantial interest because of its large exiton binding energy (60meV), which could lead to lasing action based exiton recombination even above room temperature. It can be used in solar cells, piezoelectric device, optoelectric device, transparent conducting electrodes and gas sensors. The characteristics of ZnO films can be modulated by the appropriate dopant.All the samples with good orientation were prepared by RF-magnetron sputtering. Surface morphology,crystal structure, optical and magnetic properties of ZnO based films were investigated by metallograph, SEM, ultraviolet-visible spectrum photometer, XPS and SQUID et al. The results are the following:1. ZnO films were prepared on Si(111) substrate. The as-deposited films were annealed under vacuum in the different temperature. The effects of annealing temperature (Ta) on the structure and photoluminescence properties of ZnO films were studied. The crystalline quality of the films was improved with the Ta increasing. In the photo-luminescence (PL) spectra, two violet (394 and 412 nm) and two green (560 and 588 nm) peaks were observed from the as-deposited and annealed samples. Their origin and the reason of violet peaks'shift were discussed.2. The effects of Fe doped on the structure of ZnO films were investigated. The growth mechanism of the observed fractal aggregates was discussed by three possible reasons. The effects of Ta on the structure of thicker Fe doped ZnO films which were prepared as the same conditions were studied.3. Zn_1-xCr_xO (x=0, 0.03, 0.07) films were deposited on Al2O3 substrates. The influences of different Cr content on structure, optical and magnetic properties were studied. From the XRD spectra of the samples, it was obvious that there was no second phase, the Cr ions systematically substitute for the Zn ions in the films without changing the wurtzite structure. In the room temperature PL spectra of Zn_1-xCr_xO films, there were two PL peaks located at 408nm and 554nm. The intensities of the two PL peaks increased apparently with the increase of Cr contents. We think the violet peak was found to be associated with the interface traps exacting in the depletion regions between the ZnO-ZnO grain boundaries, and the green peak originated from intrinsic defects in ZnO. Meanwhile, all Zn_1-xCr_xO films exhibited ferromagnetism at 5K. Especially, Zn0.93Cr0.07O film had ferromagnetism at 300K.