Optimization of Etching Time, Temperature of Metal Salts in Surface-texturized Silicon Fabricated Through One-Step Metal-Assisted Chemical Etching

Abstract

This study delves into the Metal-Assisted Chemical Etching (MACE) of p-type monocrystalline silicon wafers, with a focus on tailoring surface morphology for heightened performance as thermal absorbers. Employing diverse metal catalysts—specifically, nickel nitrate hexahydrate and silver nitrate salts—the investigation systematically explores the impact of catalyst type, etching time and temperature on nanostructure formation. One of the objectives was to maintain the etching temperature to be as low as possible through the application of the metal catalysts. Achieving >2 of thermal energy absorbance in the UV-Vis-NIR range required immersing samples in a nickel nitrate salt solution at room temperature for 60 minutes. Characterization through UV-Vis-NIR spectroscopy revealed reflectance and absorbance spectra, with silver nitrate salt-etched samples demonstrating exceptional performance, achieving the lowest reflectance values within the critical wavelength range of 300–1800 nm. Notably, after 60 minutes of etching, silver nitrate salt-etched samples produced reflectance values ranging from 0.19 % to 3.45 %. Optimized parameters for nickel nitrate salt-etched samples were identified at 30 minutes of etching and 50 °C, showcasing an average reflectance of 1.54 %. The consideration of energy conservation was paramount, prompting the initial observation of each catalyst's performance during the etching process with no heating at room temperature. Subsequently, in the extended phase of the study, the etching temperature was gradually increased. Raising the etching temperature served as a method of varying the process parameter to observe its impact on the formation of surface nanostructures and absorbing performance. The study concludes with recommendations for future research, advocating for the exploration of additional metal catalysts and investigation of combined catalysts.