Preparation Of Aperiodic Micro - Nanostructures On Monocrystalline Silicon Surface Based On KOH Corrosion

In the information age, silicon is the most attractive material because it exhibits many advantages of well-known technology components: nontoxicity, abundances in the earth, low cost, and long-term stability. The silicon surface microstructure is employed by alkaline solution, forming a pyramid structure which was used on the solar cell in traditional. The microstructure increased light trapping because it extended absorbing path length. The purpose of this thesis is to fabricate the nanosized microstructures that can be hopefully used to the SERS substrate of detection.The wet anisotropic etching of silicon in KOH solution is the significance technology for fabricating silicon microstructure.However, the nano-sized fabrication is very sensitive to a slight change in etching condition including the ratio of KOH and IPA, the temperature, and the reaction time. To get the nano-sized microstructure on the silicon substrate, this thesis designed the above factors under the KOH/IPA mixture solution, SEM observation and UV-2006 tested reflectivity.The first section of the paper, the lowest reflection of texturized surface was 12.30% and 13.66% on the 5% and 25% KOH respectively, 3vol% IPA, 80℃, 30 min. Next, at the 20% and 25% KOH condition, by changing the temperature from 50℃ to 80℃, the minimum size is 1.72 um with uniform microstructure when the temperature is 70 ℃. Fixed 20% KOH, 70 ℃, the homogenous and small pyramids in the textured structure of silicon crystalline by corroded 15 min. The average size has reached to 1.24 um meanwhile the reflectivity is 11.2%.The paper detailed the fabrication technique for monocrystalline silicon microstructure SERS substrate when KOH under 5% further.The surface was etched by different concentration KOH from 0.5% to 5% added with 3vol% IPA, 80℃, 30 min. The results showed that high quality microstructure is 3% KOH after a comprehensive consideration from particle and reflectance. In order to discover the IPA influence at low concentration KOH, we find that IPA can’t have huge influence within the scope of volume fraction from 2% to 4%. When the condition is 3%KOH and 2vol%IPA, the particles size is 1.37 um. The following research is about the temperature how to affect the nano-structure fabricated. With the increase of temperature, the corrosion rate showed fast first and slowly afterwards. A minimum reflectance of 12.24% is 80℃. However, when temperature is 70℃, SEM indicates that the particle diameter is 0.93 um in nanometer scale. The fabrication of nano-structure diameter and regulation can be changed by adjusting corrosion time during the silicon SERS substrate experiment. In the experiment, the minimum particle was fabricated when the experiment lasts 30 min, with nano-structure uniform distributed. For the particle distribute, the probability of microstructure from 0.4um-1.2um is 73.3% by Nano Measure software.