Erbium environment in silicon nanoparticles

The Er environment in two sets of Er-doped Si nanoparticles (np) with nominal Er concentrations of 1-2 at.% was measured by EXAFS. Set H, with a homogeneous distribution of Er atoms. consist of samples with average np diameters of 3.2. 5.9, and 6.4 mn. The np of set C consist of a Si core covered by an Er-rich shell, with average diameters of 26 and 22 nm. nearly an order of magnitude higher than those of set H. The Er atoms in the np are coordinated to oxygen, like in the Er(tmhd)(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:H(Er), indicating that the lattice constraints in the np are very similar to a-Si:H. Efficient Er.- 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 Er(tmhd)(3) and in Er2O3 but the Er-O distances are larger. (C) 2002 Elsevier Science B.V. All rights reserved.