Analysis of the Fano in diamond

The Fano appears above a critical percolation threshold corresponding to th e onset of the metallic conductivity on the boron impurity band. Its parame ters are deduced from the fit of the Raman curves of heavily boron doped ho moepitaxial diamond films. The large (10 cm(-1)) widening and red shift of the phonon originates from its strong coupling with the continuum of electr onic transitions. The strong deformation \q\ approximate to 2.2 of its Lore ntzian shape is ascribed to the Raman cross-sections relatively large for t he continuum of electronic interband transitions T, and small for the phono n Tp whose negative value induces q < 0. (C) 2001 Elsevier Science B.V. All rights reserved.