Broadband antireflection property of silicon nanocone arrays with porous sidewalls fabricated by Ag-catalyzed etching

Siliconnanocone (SiNC) arrays with porous sidewallswere successfully fabricated through a simple, low-cost Ag-catalyzed etching method. By electron spin resonance technique and TEM analysis, it has been verified that the formation of porous SiNC arrays is due to the gradual dissolution of the pristine Ag nanoislands as they sank into the Si and the lateral etching of the regenerated Ag nanoparticles to the SiNC sidewalls. Theoretical calculation results suggest that the reflectance of the porous SiNC arrays is much lower than that of the smooth SiNC arrays over wide wavelengths ranging from 300nm to 1700nm. The long-wavelength reflectance can be further suppressed by increasing surface porosity of the SiNCs and their length. Experimental test results show the lowest average reflectance of 1.7% in the wavelength range of 300-1000nm while approximately 30% in the wavelength ranges of 1200-1700nm, which is generally consistent with the theoretical results. This shows that the porous SiNC arrays had excellent broadband antireflection properties, making them attractive for a wide range of potential applications in Si-based optoelectronic devices.