Abstract
We observed photoluminescence quenching in crystalline (c) Si/amorphous (a) SiOx core-shell silicon nanowires (Si-NWs). We observed that the photoluminescence (PL) intensity strongly depends on the stoichiometry of outer a-SiOx matrix, which was characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The PL showed a broad-range emission from 1.6 to 2.4 eV with the peak centered at 2.27 eV, which quenched as the oxygen content decreased from 60.5 to 54.6 at.%. Both transverse optic and longitudinal optic signatures of Si–O–Si were shifted to lower wavenumbers, which indicate the modification of chemical networks in core-shell Si-NWs. The minority carrier life time (τ) increased from 3.4 to 7.5 µs as the diameter of core Si increased from 22 to 78 nm, indicating the decrease of trap densities and alternation trap states. The reason for PL quenching is mostly attributed to the structural and stoichiometry changes in outer a-SiOx of c-Si/a-SiOx-NW.
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