Characterization of heavily B-doped polycrystalline diamond films using Raman spectroscopy and electron spin resonance

Heavily B-doped polycrystalline diamond films ([B]>10(19) cm(-3)) are studied by Raman spectroscopy and electron spin resonance. The formation of an impurity band is accompanied by a Fano-type interference for the one-phonon scattering. Bands at 1200 and 500 cm(-1) are observed in Raman spectroscopy for concentrations above 10(20) cm(-3). They are related to maxima in the phonon density of states, and are ascribed to disordered regions or crystalline regions of very small size. The concentration of defects associated with the paramagnetic signal observed around g=2.0030 increases drastically above 10(21) B cm(-3). The Mott insulator-metal transition is accompanied by the presence of a new paramagnetic signal (g=2.0007 for 2 X 10(20) B cm(-3) g=1.9990 for 10(21) B cm(-3)) ascribed to free holes in the impurity band. (C) 1995 American Institute of Physics.