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 Mo¨ssbauer 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 et al., Phys. Rev. B 66, 085320 2002), the nature and the origin of the 1.54 microns photoluminescence signal obtained from our best samples will be analyzed in detail.