On the plasmon-assisted detection of a 1585 cm−1 mode in the 532 nm Raman spectra of crystalline α-Fe2O3/polycrystalline NiO core/shell nanofibers

Crystalline hematite/polycrystalline nickel oxide (α-Fe2O3/NiO) core/shell nanofibers are prepared by electrospinning and calcination, followed by a varying number (100-1150) of atomic layer deposition cycles of NiO. The deposition of the conformal NiO layer leads to the passivation of the surface states and the appearance of a photoluminescence band in the micro-Raman spectra excited by 532 nm laser. As a continuous NiO layer is formed, a peak, possibly arising from a two-magnon mode, appears at 1585 cm−1. The detection of the peak, which is not observed in the spectra excited by a 633 nm laser, is assisted by the surface plasmon at around 510 nm introduced by the polycrystalline NiO layer, due to the electron doping induced by coordination-defects at its edge-rich surface.