S. Schuppler et al., SIZE, SHAPE, AND COMPOSITION OF LUMINESCENT SPECIES IN OXIDIZED SI NANOCRYSTALS AND H-PASSIVATED POROUS SI, Physical review. B, Condensed matter, 52(7), 1995, pp. 4910-4925
Near-edge and extended x-ray-absorption fine-structure measurements fr
om a wide variety of oxidized Si nanocrystals and H-passivated porous
Si samples, combined with electron microscopy, ir absorption, forward
recoil scattering, and luminescence emission data, provide a consisten
t structural picture of the species responsible for the luminescence o
bserved in these systems. For porous Si samples whose luminescence wav
elengths peak in the visible region, i.e., at <700 nn, their mass-weig
hted-average structures are determined here to be particles (not wires
) whose short-range character is crystalline and whose dimensions-typi
cally <15 Angstrom-are significantly smaller than previously reported
or proposed. Results are also presented which demonstrate that the obs
erved visible luminescence is not related to either a photo-oxidized S
i species in porous Si or an interfacial suboxide species in the Si na
nocrystals. The structural and compositional findings reported here de
pend only on sample luminescence behavior, not on how the luminescent
particles are produced, and thus have general implications in assignin
g quantum confinement as the mechanism responsible for the visible lum
inescence observed in both nanocrystalline and porous silicon.