Analysis of the Fano in diamond

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