Controllable Synthesis Of Ordered ZnO Nanodots Arrays By Nanosphere Lithography

ZnO has attracted significant attention as a promising luminescent material for applications in blue and ultraviolet light-emitters and detections. Low-dimensional ZnO nanostructures have superior optical properties because of the significant exciton effects and extraordinary carrier behavior due to quantum confinement effect. But the difficulty to control the size and distribution of ZnO quantum dots reduces the properties of these devices. Thus, research on the controllable growth of ZnO nanodots is very important.In this paper, the research history of ZnO quantum dots and nanosphere lithography has been summarized. On the basis of that, we use the self-assembly-based mask for e-beam evaporating a layer of ZnO at room temperature. After the vapor passes through and interspaces among the nanospheres, the ZnO nanodots are formed on the Si substrate. The optical properties of the ZnO nanodots have been investigated. The original innovation is that the nanodots'. size can be controlled by varying the deposition time. Therefore it is a technique with the precise control of the dots' size and geometry, which has a great promise for applications in nanoscale optoelectronic device.The main content of this thesis is listed as follow:1. Ordered hexagonally patterned ZnO nanodots are triangle with the side length of 100 nm. The dot density is 1.25×10⁹ cm^-2. As for the ZnO nanodots growing for 1min, its height is about 5 nm. The obtained ZnO nanodots are of acceptable quality with high chemical purity and preferential c-axis orientation. A Photoluminescence measurement shows about 70 meV blue shift in free-exciton emission derived from low-dimensional quantum characteristics.2. The nanodots' size can be controlled by varying the deposition time. The ZnO nanodots with the growth time of 1, 2 and 3 min, exhibit different free-exciton emission at 3.378, 3.356 and 3.314 eV. In addition, the size and density can be controlled by the diameter of the nanospheres used in the method. When the diameter increases from 496 nm to 1040 nm, the size increases from 120 nm to 300 nm and the density decreases from 1.1×10⁹cm^-2 to 2×10⁸ cm^-2. Therefore it is a technique with the precise control of the dots' size and geometry.3. Different ZnO nanostructures have been fabricated by nanosphere lithography with different deposition methods. The periodical patterned reticular ZnO nanostructure is formed after magnetron sputtering deposition. And the ordered patterned porous ZnO nanostructure is fabricated by pulsed laser deposition. These periodical arrays of materials are like 2-dimension photonic crystals, which can control the light propagation.