Study And Fabrication Of Micro-and Nano-structures For Antireflection

To improve the conversion efficiency of solar cells, the research of fabrication ofanti-reflective structures on silicon surface has been becoming a hot topic. Many kinds ofmicro-and nano-structures have been studied including pyramid, nanopillar, nanoconestructures, etc. Insects like moth, have developed skills to avoid the discovery by predators.Research shows that no obvious reflection can be recognized from the insect eyes from alldirections and in the whole light spectrum.“Moth eye” effect improves the investigation ofantireflection. Many kinds of techniques have been developed to fabricate thesub-wavelength antireflection structures with graded refractive index. In this thesis, basedon the research of combination of disordered micro-and nano-textures of single-crystalsilicon, we developed the combination of ordered micro pyramid structures and disorderednanostructures by combining the anisotropic alkali etching of single-crystal silicon andnano-metal-assist chemical etching. Lower reflectivity was achieved than the disorderedmicro-and nano-textures.(1) By two-beam laser interference lithography, we fabricated three kinds of Si3N4mask structures with different duty cycle to study the influence of the duty cycle to thefabrication of microstructures by anisotropic etching. The period of the orthogonal maskstructures was5μm. By using mask assist lithography, we fabricated hexagonal Si3N4mask structures with period of9μm.(2) The mechanism of anisotropic etching on single-crystal silicon, and theoptimization of the etching were studied in detail. NaOH etchant and Si3N4mask wereused. Both orthogonal and hexagonal structures were fabricated. We studied the role of theduty cycle of the etching mask on the fabrication of ordered micro-pyramid structures onsingle-crystal silicon. (3) We optimized the rapid thermal annealing of Au film to form uniform Aunanoparticles, which act as nano-mask for metal assisted chemical etching. Nanostructureson the surface of single-crystal silicon were fabricated.(4) Based on the optimizing of the above techniques, by gold particles assistedchemical etching with HF, we combined ordered uniform micro-pyramid structures anddisordered nano-structures on single-crystal silicon. Antireflection of different structureswas studied.