Study And Preparation Of ZnO Nanostructure Films By Aqueous Solution Route

ZnO is a direct band-gap semiconductor (Eg=3.3eV at RT) with a high exciton binding energy of about 60meV. The feasibility of using excitionic lasers of ZnO at RT has been demonstrated. Besides, ZnO thin films can be prepared at temperature lowerthan 600℃, its growth temperature is lower than GaN, SiC and otherⅡ-Ⅳsemiconductor materials. Owing to these properties, ZnO can be used as room temperature short wavelength ophotoelectron material. It has been investigated extensively because of its interesting electrical, optical and piezoelectric properties making suitable for many applications such as light emitting diodes, photodetectors, electroluminescence, transparent conductive film, surface acoustic waves device and so on. The renewed interest of ZnO film is fueled since room temoerature lasing was reported by Tang et al.In this thesis, high quality ZnO films were synthesized successfully by a two-step aqueous solution routes on silicon and pre-treated sapphire, which were etched in the acid solution before heated in the N2 ambience, respectively. X-ray diffraction, room temperature photoluminescence (PL), scanning electron microscopy (SEM) and atom force microscopy (AFM) were applied to analyze the quality of the ZnO films and the surface states changing of sapphire substrates with different treating processes. The results are summarized as follow:(a) A two-step aqueous solution process was adopted to prepare two-dimensional homogeneous hexagonal ZnO nanosheets on Si (100) substrates at different aqueous growth times. The characterization showed that the as-obtained ZnO hexagonal shaped nanosheet films are of single crystalline wurtzite structures; they grow within the (0001) plane to form the regular hexagonal nanosheets and the shape is not changed with the extended solution reaction time besides the increasing (0001) plane area and thickness; these nanosheets show sharp intrinsic ultraviolet excitonic emission peaks centered around 379 nm at room temperature with all the samples, and a extremely suppressed visual emission parts are also detected. These results demonstrated that the single-crystal quality hexagonal ZnO nanosheets with good UV emitting property can be easily synthesized by our two-step method.(b) A two-step aqueous solution process was adopted to prepare ZnO films on Si (100) substrates at different magnetron sputtering times. The effect of different seed layers sputtering times on the optoelectric property of the ZnO films was studied. The growth behavior of ZnO seed layers deposited at different sputtering times was analyzed by the SEM and AFM systematically. (c) A facile route to prepare high quality ZnO films on sapphire substrates was developed by etching the substrates, followed by treating in the N2 ambience, and finally putting in the suitable growth medium. We focused on the changing of sapphire morphology and the growth of ZnO film with the different acid etching conditions. The characterization results show that high quality ZnO films could be prepared with our method. Atomic force microscope results showed that the well treated sapphire substrates could be got under the condition of etching at 100℃and sustaining about 40 min. Room-temperature measurements of the photoluminescence (PL) spectra showed that a sharp intrinsic ultraviolet excitonic emission peak centred at 380 nm. No obvious visible emission region corresponding to the defects was detected.