Preparation And Optical Properties Of Zinc Oxide / Silicon Nano-hole Pillar Array Heterostructure Composite System

Silicon based ZnO composite material is currently a hot topic of research in the field of the semiconductor optoelectronic materials. Regularly arrayed zinc oxide/silicon nanoporous pillar array (ZnO/Si-NPA) heterostructure were prepared through evaporating zinc single crystals on Si-NPA substrate followed by an annealing process in pure oxygen environment. There were two different ZnO/Si-NPA nanocomposite heterostructure characteristics, and their optical absorption and photoluminescence properties of the system are studied. Through studying these composites preparation and optical properties, ZnO/Si-NPA is expected to become the special silicon-based photoelectric materials. The study includes the following aspects:1. Preparation and structural characteristics of patterned ZnO/Si-NPA heterostructuresSilicon nanoporous pillar array (Si-NPA) was prepared by using a novel hydrothermal technique. The experimental methods of preparating ZnO/Si-NPA heterostructures concluded two steps: evaporating zinc single crystals on Si-NPA substrate and following an annealing process in pure oxygen environment. By controlling the thickness of evaporating Zn single crystals, two different structure characteristics were prepared: 1) ZnO growth concentrated on the top of each silicon pillar, when Zn films thickness was about 50 nm; 2) when increase the deposited volume of Zn, there was continuous ZnO fims covering on the substrate surface, just like the "theater curtain" .2. Optical properties of patterned ZnO/Si-NPA heterostructuresThe above two different structural ZnO/Si-NPA heterostructures had their own unique optical properties. For ZnO/Si-NPA with Zn selective growth on the top pillars, its photoluminescence properties were the composite luminescent of the ZnO and Si-NPA substrate, respectively. But the "theater curtain" structural ZnO/Si-NPA only showed the luminescence properties of ZnO crystalline.3. Variation of on the optical properties of ZnO/Si-NPA as a result of thermal annealing in pure oxygenThe photoluminescence (PL) and optical absorption properties of ZnO/Si-NPA were highly depending upon the annealing temperature adopted in sample preparing process. To find the influence of the annealing conditions, the prepared Zn/Si-NPA samples were oxided about 120 min at 200℃, 400℃, 600℃, 700℃and 800℃, respectively. When the annealing temperature is below 400℃or above 700℃, the PL would be mainly attributed to the light emission from Si-NPA substrate or ZnO film, respectively, but the PL originating from both Si-NPA substrate and ZnO film is simultaneously observed as the sample being prepared with an annealing temperature of 600℃. Our experimental results show that the PL of ZnO/Si-NPA heterostructures could be effectively controlled through changing the annealing conditions adopted in the preparing process, which might be of practical importance in fabricating optoelectronic devices in future.