Vanadium-doped And Vanadium-nitrogen Co-doped Zno Thin Film Properties

The ferromagnetism semiconductors with Curie temperatures above room temperature are important spintronic materials for next generation of microelectronic photoelectronic devices. Theoretical calculations and the experiments indicated that vanadium-doped zinc oxide could be ferromagnetic with Curie temperature above 300 K and introduction of holes was benefit to the ferromagnetic stability. Due to its high exciton binding energy (60 meV), zinc oxide thin films have efficient excitonic emission at room temperature or above. Therefore, it is possible to integrate magnetic and optical properties into a device with ZnO. The problem is how to obtain high quality thin films with such properties.In the thesis, V-doped zinc oxide thin films were deposited on glass substrates by DC-reactive co-sputtering. The effect of V doping on the structural and optical parameters of ZnO thin films was studied. Considering that the introduction of holes is advantageous to ferromagnetic stability, V and N co-doped zinc oxide thin films were deposited on glass substrates by RF and DC co-sputtering. The effect of vanadium target power and annealing process on the structural and optical properties of ZnO thin films was investigeted.The main results and conclusions are as the following: 1. Investigation on V-doped zinc oxide thin films(1) The thin film with lower V atom percentage (1.74at.%) has a highly c-axis orientation and comparatively good crystallization. When V contents are increased, c-axis orientation of the films gets worse. V atoms, substituting for Zn atoms distribute uniformly in ZnO crystal lattice. All the V-dopped ZnO thin films are compressively stressed and the compressive stress increases with vanadium content.(2) The film with lower V atom percentage has higher optical transmittance in specific wavelength range. Refractive index is lowered firstly and then increased, the extinction coefficient rises, the transmittance falls, and optical band gap rises a little bit firstly and then reduces obviously with increase of the vanadium content. This indicates that optical constants of V-dope ZnO films can be controlled by varingVanadium content.2. Investigation on V and N co-doped zinc oxide thin films(1) V and N co-doped ZnO films deposited under lower vanadium target power (30W) have comparatively better crystallization and higher optical transmittance. The crystallization of the films gets worse as vanadium content is increased. The optical band gap increases linearly as the vanadium target power, which shows that optical band gap of V and N co-doped ZnO films can be tuned by controlling vanadium target power. V and N co-doped ZnO films deposited under lower vanadium target power have stronger ultraviolet emission and weaker blue and green emissions, which displays relatively better optical property.(2) Crystallization and optial quality of V and N co-doped ZnO films can be obviously improved by annealing. The crystallization improves and the optical transmittance ascends while the optical band gap falls with increasing annealing temperature. Ultraviolet emission of the V and N co-doped ZnO film after annealing at 550℃is evidently enhanced, accompanied by blue, green and red emissions. This illuminates that the annealing improves the property of photoluminescence of V and N co-doped ZnO films though certain defects still exist.