Visible and IR photoluminescence of c-FeSi@a-Si core-shell nano-fibres produced by vapour transport

The procedures for the synthesis of amorphous ε-FeSi/Si core-shell nanofibres by vapour transport in a CVD configuration are reported. Crystallite studies by the Williamson-Hall method show the sizes to be typically about 8.0 nm which agrees with TEM value of 7.9 nm fibre diameter with a compressive strain of about 0.04. Features in the photoluminescence of these FeSi core-shells in both visible and IR are at 410 nm, 1062 nm, 1414 nm and 1772 nm and absorption feature at 1000 cm−1 from FTIR are explained from density functional theory (DFT) ab initio calculations. PL confirms the intra-band transition whereas FTIR agrees perfectly with the band-to-band transition whose band gap energy is 0.13 eV for FeSi. FTIR also unveils inter-band transition which DFT calculation could not predict. Raman spectroscopy data confirm FeSi and nano-Si presence.