Confinement effects in crystallization and Er doping of Si nanostructures

This article presents our comprehensive investigation of the crystallizatio n of amorphous silicon films with a layer thickness below 20 nm from an exp erimental as well as from a theoretical point of view. The exponential scal ing of the crystallization temperature with layer thickness is derived by u sing solid state crystallization theory. The critical height of the nanocry stals embedded in such superlattice structures depends on the specific inte rface free energies of the respective phases (oxide, amorphous Si. and crys talline Si) and exponentially on the layer thickness. In addition, strong e nhancement of room temperature luminescence from Er ions embedded in the vi cinity of Si nanocrystals is shown. Spatially resolved photo luminescence i nvestigations and Rutherford backscattering measurements for Si and Er dist ributions along the same line scan clearly manifest that inhomogeneities in implantation are not the cause of the correlated increase of Er and decrea se of nc-Si luminescence. However, this effect can be understood as a coupl ing of radiative processes, which includes an energy transfer from Si nanoc rystals to Er ions. (C) 2001 Elsevier Science B.V. All rights reserved.