Luminescence from beta-FeSi2 precipitates in Si. I. Morphology and epitaxial relationship

The goal of this paper is to investigate the morphology and the structure of ion-beam synthesized beta-FeSi2 precipitates and the defects in the Si matrix by using transmission electron microscopy (TEM) and, in a few cases, conversion electron Mossbauer spectroscopy or Rutherford backscattering spectrometry. We shall point out how the different process parameters affect the resulting structure and the optimum process window for light emitting application of beta-FeSi2. In particular, we will also show that within the optimum process window at least two different types of precipitates are obtained in separate regions: small ball-shaped precipitates in the surface region and large disc-shaped precipitates deeper in the sample. The latter are shown to display a very good interface to the Si matrix, as obtained by TEM analysis and dedicated molecular dynamics simulation. In the second part of this paper [Martinelli , Phys. Rev. B 66, 085320 (2002)], the nature and the origin of the 1.54-mum photoluminescence signal obtained from our best samples will be analyzed in detail.