Preparation, Performance And Device Investigation On Cu Doped And Cu-N Codoped ZnO Nano-materials

Cu doped ZnO is a semiconductor with great potential in areas such as optoelectronics and spintronics for its unique optical, electrical and magnetical properties. In addition, co-doping with appropriate elements can effectively affect the performance of materials. In this work, we prepared vertically aligned ZnO and ZnO:Cu nanorod arrays through electrochemical deposition and vapor phase transport method. We also fabricated ZnO:Cu single nanowire FETs and Cu-N codoping ZnO nanorod arrays. A detailed investigation on the optical, electronical and magnetic properties of Cu doped ZnO has been made.The primary results are described as following:1. We have prepared ZnO and ZnO:Cu nanorod arrays with good crystalline quality by optimizing growing conditions. Annealing temperature-dependent photoluminescence spectra indicate the nanorods annealed under300℃show the best quality. Room temperature ferromagnetism (RTFM) is observed in all ZnO:Cu samples and the magnetism decrease with the enhance of Cu concentration.2. Cu-N codoped ZnO nanorod arrays are synthetized by annealing the ZnO:Cu nanorods under atmosphere of nitrogen source. N is confirmed being doped into ZnO by XPS mesurements. Significantly enhanced RTFM is observed in Cu-N codoped ZnO nanorods.3. ZnO:Cu nanowire arrays have been prepared by vapor phase transport method with post-diffusion and annealing, and we suggest that the approach with a diffusion in low vacuum followed annealing in Ar atmosphere is more conducive to the realization of uniformly doped ZnO:Cu systems. The influence of post-annealing of ZnO:Cu nanowires on the optical and magnetical properties has been investigated and combining with the ESR results we conclude that many defects except for CuZn appear, such as Vo and Zn.4. Based on the ZnO:Cu nanowires, we have fabricated single nanowire FETs. The nanowires are n type with a low carrier concentration. The carrier concentration decrease with the enhance of copper contents. An obvious optical response is also observed which is considered have great connection with the valence of Cu.5. A discussion has been made on the origin of the room-temperature ferromagnetism in Cu doped ZnO and it can be explained by defects related bound magnetic polar (BMP) and double exchange mechanism based on copper ions with different valences.