Localized absorption in aluminum mask in visible spectrum due to longitudinal modes in vertical silicon nanowire arrays

摘要

Localized optical absorption in aluminum masks used for vertical silicon nanowire fabrication is demonstrated experimentally and supported using computer simulations. The mask is in the form of 30 nm thick aluminum nano-disks on top of silicon nanowires arranged in square lattices. The nanowires are 1 μm long, with diameters ranging from 60 nm to 100 nm and spaced 400 nm apart. New spectral features appear in the 500 nm-700 nm wavelengths range and are dependent on both the nanowire diameter and length. The former is due to the excitation of radial modes, whereas the latter stems from longitudinal (Fabry-Perot) resonances. The salient features associated with absorption in the aluminum mask and the role nanowire plays in this connection are discussed.