Bunching characteristics of silicon nanowire arrays

Ordered arrays of silicon nanowires were fabricated by etching, and their bunching characteristics were parametrically studied by varying the diameter, the length, and the pitch. The diameter to length ratio was found to be critical for the nanowires to stand vertically without bunching. For a length of 650nm, 40nm and larger diameter nanowires were vertical, whereas for a length of 400nm, 34nm and larger diameter nanowires were vertical. Further, the phase change between the bunching and vertical nature of nanowires happens abruptly and was verified by finite element modeling of the deflections of the nanowire tips for different diameters. The detailed experimental study provides guidelines for silicon nanowire arrays being considered for different applications including solar cells, optical waveguides, and sensors.