Structure and electronic properties of SiO2/Si multilayer superlattices: Si K edge and L-3,L-2 edge x-ray absorption fine structure study

We report an x-ray absorption fine structure study at the Si K and L-3,L-2 edges of a series of Si/SiO2 superlattices (SL). The SL system comprises four periods of elemental silicon with a spacing of 1, 1.4, 2.2, and 2.6 nm sandwiched by a 1.5 nm silicon oxide and capped by a 3 nm silicon oxide layer. These systems exhibit electroluminescence and photoluminescence. X-ray absorption near edge structure (XANES) at both the Si K and L-3,L-2 edge confirms that the Si layers are amorphous. Polarization dependent measurement at the Si K edge reveals that a distinct Si/SiO2 interface exists with strong Si-O bonding oriented preferentially closer to the surface normal. High resolution XANES at the Si L-3,L-2 edge shows a noticeable blueshift of the edge threshold as the lattice spacing decreases, in good accord with quantum confinement. The results and their implications for the origin (quantum confinement and interface/oxide defects) of luminescence in these superlattice systems are discussed. (C) 2002 American Institute of Physics.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000177683000010&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, AppliedSCI(E)EI21ARTICLE63000-30069