Erbium environment in silicon nanoparticles

The Er environment in two sets ofEr-doped Si nanoparticles (np) with nominal Er concentrations of1–2 at.% was measured by EXAFS. Set H, with a homogeneous distribution ofEr atoms, consist ofsamples with average np diameters of3.2, 5.9, and 6.4 nm. The np ofset C consist ofa Si core covered by an Er-rich shell, with average diameters of26 and 22 nm, nearly an order ofmagnitude higher than those ofset H. The Er atoms in the np are coordinated to oxygen, like in the ErðtmhdÞ 3 organometallic precursor. In set H, both the Er coordination and the average Er–O separation increase as the average nanoparticle diameter increases from 3.2 to 6.4 nm. The results for small np are remarkably similar to those found for Er in a-Si:HhEri, indicating that the lattice constraints in the np are very similar to a-Si:H. Efficient Er 3þ luminescence is detected in as-prepared samples. As the particle size increases the Er environment becomes Er2O3-like, as in bulk Czochralski silicon. In set C, the Er environment in both samples is similar to that in ErðtmhdÞ 3 and in Er2O3, but the Er–O distances are larger. 2002 Elsevier Science B.V. All rights reserved.