Preparation And Characterization Of One-dimensional Silicon Nanomaterials And ZnO/Silicon Nanowire Heterojunction

One-dimensional silicon nanomaterials have good photoluminescence properties at room temperature. Due to its unique nanostructure, it hopes to replace the electrical interconnection used currently by optical interconnection in the semiconductor industry, so the running rate of the integrated circuit will be improved greatly. Another interesting feature of such structure is the significant suppression of reflection over the visible-light spectral range, which can be used as an efficient antireflection coating for the silicon solar cell. On the other hand, three-dimensional p-n junction incorporating silicon nanomaterials has a large junction area, which makes the photocarrier concentration increase greatly and short circuit current improve effectively. One-dimensional silicon nanomaterials will be the cornerstone of the future semiconductor industry.In this paper, One-dimensional silicon nanowire arrays (SiNWs) were grown by noble metal-assisted wet chemical etching on p-type silicon substrate at room temperature. The influences of concentration of H2O2 and Ag ion and time of etching on the SiNWs morphology and properties were studied. To further improve the morphology of SiNWs, the electron beam evaporation and rapid thermal annealing (RTA) were used to control the morphology of silver nanoparticles deposited on the silicon substrate. The ZnO/SiNWs heterojunction was achieved by magnetron sputtering and sol gel method, respectively, and the photoelectric properties of such heterojunction were studied. The main results are obtained as follows:1. SiNWs were prepared by noble metal-assisted wet chemical etching on p-type silicon substrate at room temperature. When the concentration of HF/AgNO3 mixed solution were 4.6mol/L and 0.01mol/L, respectively, and the depositon time of silver nano-network was 60s, then the concentration of HF/H2O2 mixed solution were 10wt% and 2.1 wt%, respectively, and the time of etching was 20min, the diameter of SiNWs was about 50-200nm, and the length of that was about 8μm. The length of silicon nanowire was proportional to the etching time, and the etching rate is about 360nm/min, then the diameter of silicon nanowire and density of SiNWs could be changed by optimizing the concentration of H2O2 and deposition time of Ag nano-network. When the concentration of H2O2 was increasing graduallly. the density of SiNWs became smaller and smaller, and also the diameter of silicon nanowire decreased. The depositon time of Ag nano-network also could have such character like the concentration of H2O2. The reflectance of SiNWs was not more than 5% range 200～1200nm.2. By depositing silver thin film, annealing to control the morphology of silver nanoparticles, and finally etching by HF/H2O2 mixed solution. One-dimensional silicon nanoholes were prepared on silicon substrate. The Ag nanoparticles were achieved successfully from Ag nano-network by changing the thickness of Ag thin film deposited by electron beam evaporation and the annealing temperature of RTA. The uniform silicon nanoparticles (50～100nm) were prepared when the thickness of Ag film was 20nm and the annealing temperature was 800℃, then silicon nanohole arrays were achieved after chemical etching. The nanoholes structure not only maintained the reflection characteristics of SiNWs, but also had a higher mechanical strength, which made it a promising material in the photovoltaic field.3. ZnO/SiNWs heteroj unction was prepared by magnetron sputtering and sol gel method, respectively. It’s critical to optimize the structure of Ti/Au electrode to improve the electrical properties of the heterojunction. The contact resistance of the heteroj unction prepared by magnetron sputtering was relatively smaller than that by sol gel method. The reason was that metal electrode deposited on ZnO/SiNWs heterojunction preparaed by magnetron sputtering was relatively smooth and compact, while the metal electrode deposited on ZnO/SiNWs heterojunction preparaed by sol gel method had an island-structure, which made it reflect large reverse leakage current and poor rectifying properties during testing. It was also found that the ZnO photoluminescence properties were enhanced when the SiNWs were used as substrate to deposite ZnO thin film. Both the increased surface area and the anti-reflective characteristics inherent to the nanowire structure were believed to be responsible for enhancement in emission intensity.