Large arrays of ultra-high aspect ratio periodic silicon nanowires obtained via top–down route

Metal-catalysed etching (MCE) is a simple and versatile method for fabrication of silicon nanowires, of high structural quality. When combined with laser interference lithography (LIL), large areas of periodic structures can be generated in only few steps. The aspect ratio of such periodic structure is however commonly not higher than several decades or very few hundred. Here, a combined MCE and LIL techniques were applied to fabricate dense (4 × 108 cm−3), periodic arrays of vertically aligned silicon nanowires with aspect ratio of up to 103. This is a considerable higher number than previously reported on for periodic silicon wire arrays prepared with top–down approaches. The wires were slightly tapered, with top and bottom diameters ranging from 370 to 195 nm and length of up to 200 μm. A potential use of the nanowires as light absorber is demonstrated by measuring reflection in integrating sphere. An average total absorption of ~97 % was observed for 200-μm-long wires in the spectral range of 450–1000 nm. A comparison to simulated absorption spectra is given.