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Structure and electronic properties of SiO2/Si multilayer superlattices: Si K edge and L3,2 edge x-ray absorption fine structure study

2002; American Institute of Physics; Volume: 92; Issue: 6 Linguagem: Inglês

10.1063/1.1501742

1520-8850

Ramaswami Sammynaiken, S. J. Naftel, Tsun‐Kong Sham, Kok‐Wai Cheah, B. Averboukh, R. Huber, Y. R. Shen, G. G. Qin, Z. C., W. H. Zong,

Semiconductor materials and interfaces

We report an x-ray absorption fine structure study at the Si K and L3,2 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 L3,2 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 L3,2 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.