| Wurtzite zinc oxide (ZnO), as a well-known wide direct band gap (about 3.37 eV) ?-? compound semiconductor, has attracted considerable interest in recent years. Due to its large exciton binding energy of 60 meV at room temperature, ZnO has been recognized as an ideal material for short wavelength optoelectronic devices. Unfortunately, the high formation energy and serious self-compensation of the p-type doping, along with a large amount of donor-like native defects and impurities, have become the major scientific issues and technical difficulties in the development of ZnO. Another important feature of ZnO is that it possesses a rich family of nanostructures with a series of novel and unique properties. Compared with ZnO films, the nano-structured ZnO materials with large surface to volume ratio have a higher density of surface states, which is more chemically active, resulting in lower formation energies of p-type doping or related defects. Therefore, nano-structured ZnO materials may provide an alternative to realize considerable doping efficiency, which is helpful to solve the technical difficulties of p-type doping in ZnO.In the thesis, the synthesis and doping of one dimensional ZnO nanostructures were studied. We investigated the chemical configuration, structural and optical properties of intrinsic and nitrogen (N) doped ZnO micro-/nano-rods array systematically. We also discussed the behaviors of native point defect zinc interstitial (Zni) and zinc vacancy (Vzn), and focused on the techniques and methods which could effectively control the formation of Zni or VZn related intrinsic donors or acceptors. Detailed results are listed below:(1) The controlled syntheses of undoped and N-doped ZnO micro-/nano-rods were investigated. With the optimized growth conditions, vertically aligned intrinsic ZnO micro-/nano-rods have been homoepitaxially grown on a high-quality ZnO template via chemical vapor transport method without employing any catalysts. N2O was employed as both N and O precursors for the growth of N-doped ZnO micro-/nano-rods, and the N incorporation was confirmed. All the as-grown samples are oriented along the c-axis with a well-ordered wurtzite structure, and exhibit excellent crystalline.(2) The structural, vibration, and optical properties of N-doped ZnO micro-/nano-rods were thoroughly studied, and we obtained the behaviors of native point defect Zn; and VZn. The inner correlation between the native defects and the optical properties of ZnO material was revealed. And the comprehensive characterization methods were established to study the properties of Zn; and VZn.The emissions originated from shallow acceptor VZn clusters were identified in the photoluminescence spectra of N-doped ZnO micro-/nano-rods, which means the N incorporation is beneficial to the formation of VZn clusters. Meanwhile, we found that the origin of the green band emissions with fine structure is the radiative transitions from the ground and exited states of the shallow donor Zni recombining with deep acceptor isolated VZn.(3) The techniques and methods which could effectively control the formation of intrinsic defects were investigated and obtained, including the suppression of intrinsic donor and the introduction of intrinsic acceptor. The properties of N-doped ZnO micro-/nano-rods grown with different VI/II ratio were studied, and we proposed that the shallow donor Zn; could be suppressed while the shallow acceptor Vzn clusters could be promoted via controlling the key technical parameter of VI/II ratio.(4) Through comprehensive comparison between spatially resolved and depth resolved cathodoluminescence spectra, we found the luminescent inhomogeneity and the local distribution of VZn related intrinsic acceptor in N-doped ZnO microrod with a core-shell structure. The free excitons recombination mainly come from the core of microrod, while the emissions related with VZn clusters and isolated VZn mainly come from the shell region, which means VZn related intrinsic acceptor mainly distribute in the surface area of N-doped ZnO microrod.(5) The isovalent-acceptor codoping technique has been introduced into ZnO micro-/nano-rods. The tellurium (Te) and N co-doped ZnO micro-/nano-rods were grown by chemical vapor transport method, and the influence of Te in the regulation of donor and acceptor was revealed. It was found that the shallow donor Zni could be efficiently suppressed, while N solubility could be enhanced via controlling the doping content of Te, which is a feasible technical route to realize p-type ZnO in the future. |
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