Preparation And Photoelectric Property Study Of Silicon Nanowires And Silicon Nanoholes With Periodical Structure

Compared to the traditional bulk silicon material, nano-crystalline silicon material such as Si nanowires, nano-pyram, nanoholes, has become a hot research field due to their unique photoelectric properties.In this work, two-dimensional PS sphere arrays template is used to graphic crystalline silicon on the wafer surface, and SiNHs and SiNWs were fabricated via reactive ion etching（RIE） and metal catalytic etching, respectively. The experimental conditions affecting the self-assembly of two-dimensional polystyrene sphere（PS） arrays were studied, and large area-ordered PS template with close-packed structure were prepared on Si surface. The content and results were showed as follow:（1） Evaporation self-assembly method was used to fabricate high-quality polystyrene microsphere colloid crystal and using ethanol as disperse medium. The preparation condition of High quality monolayer colloidal crystals template was studied by changing characteristics of substrate surface, particle size,ratio of ethanol. For PS dispersant with 2.5wt% concentration, the best ratio of alcohol volume for 500nm-PS and 1000nm-PS were 50% and 45%, respectively. The best optimum etching power was 40 W.（2） The reaction procedure between Si and etching gases was studied systematically, which SF6 is the main etchant of silicon wafer, O₂ is both act as diluent and protecting sidewalls. The more RF-power of RIE, the more the density of gas radial, the faster the rate of etching, but the worse directivity of etching. The key to solving the cluster problem of nanowires is to control the depth-width ratio below 70, and the etching rate under the optimal condition is 60nm/s.（3） The antireflective properties of Si NHs and SiNWs were investigated carefully, and size and periodicity affect trapping effect directly. Both actual measured data and simulated data supported that the periodicity of SiNHs depended on the minimum value of reflectivity. At the same time, the reflectivity of the Si NWs increases with the length. Compared to the planar Si, the nanohole arrays structures and nanowire arrays exhibit outstanding broad anti-reflection properties in a wide spectrum range. It is evident that both nanostructures drastically suppress the reflection across the whole measured spectrum with wavelength above Si band gap（1.12 eV）, which the reflection is less than 6%.（4） Several surface modification such as coating TiO₂ film, decorating gold particle, depositing a-Si:H layer were performed on SiNWs to further improve the photoelectric properties.