Characteristics Of ZnO Nano-Films Growth And The Impurity Modulation

ZnO is a direct wide-bandgap semiconductor,and the application of ZnO in optoelectronic devices is fueled owing to the bandgap energy at ultraviolet range.The large exciton binding energy(60 meV)of ZnO makes the realization of laser emission and other optoelectronic devices at room temperature possible.The property that ZnO is easily etched in acids and alkalis provides an opportunity for the fabrication of smallsize devices and integrated circuit.In addition,the much simpler crystal-growth technology of ZnO results in a potentially low cost for ZnO-based devices.ZnO has a bright potential in optoelectronic application,and the growth of high quality,low defect density ZnO nanomaterials and impurity energy level modulation plays a key role in the device application.In the thesis,the ZnO nano-films were synthesized through chemical vapor deposition(CVD)method,and the growth characteristics were characterized by using cathodoluminescence(CL)and other methods.The electron beam(e-beam)irradiation was applied to modulate the amphoteric impurity energy levels of Cu in Cu incorporated ZnO(ZnO:Cu)films.The achievements in our work include:1.ZnO films were grown by a CVD method,and the crystallization characteristics of ZnO films epitaxially grown on GaN and sapphire substrates with different orientations were investigated.Most importantly,CL measurements reveal the three stages during the growth of ZnO films on c-plane GaN substrate,which helps to understand the mechanism of film growth.2.High crystal quality,low defect density ZnO nanowire arrays were grown on GaN substrate by using CVD method.Heavily incorporation of Ga atoms into ZnO nanowires from the GaN substrate was observed.The difference of Ga distribution between axial and radial directions indicates the essential role of surface diffusion in the incorporation process.Furthermore,the simulation of the diffusion dynamics exhibits that the existence of abundant oxygen vacancies on ZnO sidewalls results in the apparent decrease of diffusion barriers,which enhances the surface diffusion extraordinarily.3.Low-energy e-beam irradiation was used in the modulation of amphoteric impurity energy levels of Cu in ZnO:Cu films at nanoscale level,and the significant enhancement of blue emission was achieved.The conversion characteristics of the Cu states under e-beam irradiation was presented,which provides novel approaches for real-time manipulation semiconductor properties with nanoscale accuracy.In this thesis,the growth characteristics of ZnO nano-films was investigated with CL and other characterization methods.Three stages growth of ZnO films and the incorporation of Ga atoms form GaN substrate are observed.E-beam irradiation is used in the modulation of amphoteric impurity energy levels of Cu in ZnO:Cu films.The investigations on the growth characteristics and impurity modulation facilitate further applications in optoelectronic devices.