Spectroscopic investigations of arrays containing vertically and horizontally aligned silicon nanowires

The properties of nanowire arrays have been investigated mainly in comparison with isolated nanowires or thin films, owing to the difficulty in controlling the nanowire alignment. In this study, we report on arrays containing vertically or horizontally aligned silicon nanowires, whose alignment and structure were determined using x-ray diffraction and scanning electron microscopy. The Raman spectra of the nanowire arrays differ from those of isolated nanowires because of distinct heat dissipation rates of the absorbed energy from the laser, in agreement with recent theoretical calculations. The tailored alignment of the nanowires on solid substrates up to 1 inch of diameter also enabled the observation of resonance modes associated with light trapped into the nanowires. This was proven by comparing the light absorbed and scattered by the arrays, and may be exploited to enhance light harvesting in tandem solar cells. Significantly, the control of the assembly of nanowire arrays may have a direct impact on bottom-up technologies of high anisotropy nanomaterials.