X-ray absorption fine structures(XAFS)and X-ray excited optical luminescence(XEOL)at the Si K and Si L3,2 edge have been used to investigate the optoelectronic properties of Silicon nanowires.Although no noticeable blueshift of edge jump was observed in XAFS,a less steep rise and the blurring of spectral features was observed,indicating considerable degradation in the long-range order and small size effects.XAFS probes the average of a distribution of wires of various sizes of which the majority is too large to exhibit detectable quantum confinement behavior.The results of XEOL indicates that the luminescence of Si nanowires originate from the encapsulating silicon oxide,the quantum-confined silicon crystallites embedded in the oxide layer,and the interface states between silicon and silicon oxide.