Nanostructured black silicon and the optical reflectance of graded-density surfaces

作者：Branz Howard M^*; Yost Vernon E; Ward Scott; Jones Kim M; To Bobby; Stradins Paul

来源：Applied Physics Letters, 2009, 94(23): 231121.

DOI：10.1063/1.3152244

• catalysts
• elemental semiconductors
• etching
• nanoparticles
• optical constants
• porosity
• reflectivity
• silicon

We fabricate and measure graded-index "black silicon" surfaces and find the underlying scaling law governing reflectance. Wet etching (100) silicon in HAuCl(4), HF, and H(2)O(2) produces Au nanoparticles that catalyze formation of a network of [100]-oriented nanopores. This network grades the near-surface optical constants and reduces reflectance to below 2% at wavelengths from 300 to 1000 nm. As the density-grade depth increases, reflectance decreases exponentially with a characteristic grade depth of about 1/8 the vacuum wavelength or half the wavelength in Si. Observation of Au nanoparticles at the ends of cylindrical nanopores confirms local catalytic action of moving Au nanoparticles.

• 出版日期2009-6-8