About the origin of the low wave number structures of the Raman spectra of heavily boron doped diamond films

Ultimate Metastable Solubility of Boron in Diamond: Synthesis of Superhard DiamondlikeBC5

“…2(b)] is different from that of pure diamond (one prominent À 0 25 band at $1332 cm À1 ), but is very similar to the spectrum of boron-doped diamond ($2 at% B) [18]. To date, the Raman spectra of such phases are not well understood.…”

Raman scattering in boron-doped single-crystal diamond used to fabricate Schottky diode detectors

“…The phonon density of states of diamond presents a main asymmetric maximum around 1250 cm À 1 and secondary maximum around 550 cm À 1 and hence their origin has been attributed to the relaxation of selection rules induced by the high boron content [18]. Later, Bernard et al [16] have proposed that the 500 cm À 1 band originates from local vibration modes of boron pairs. Fig.…”

“…In B-doped diamond films, both polycrystalline and homoepitaxial, the diamond Raman line displays increasing asymmetry and shifts to lower frequency with increasing B concentration [12,14,15]. The Raman spectrum of heavily B-doped diamond exhibits not only a pronounced asymmetry and downshift of the ''1332 cm À 1 '' Raman line, but also two broad bands centred at approximately 500 cm -1 and 1225 cm À 1 and another one of small intensity centred at approximately 1000 cm À 1 [14,16,17]. Fig.…”

“…The frequency position, o, and the full width at half maximum, G, of the peaks are reported in Table 1. The asymmetric broadening and the downshift of the one-phonon Raman line of B-doped diamond observed both in polycrystalline and in homoepitaxial samples [14][15][16]19], have been explained as the result of a Fano-type discrete-continuum interaction between the discrete zone-centre phonon state and the continuum of the electronic states induced by the presence of the dopant [15,17,19,20]. Moreover, dopant incorporation at substitutional or interstitial sites can produce stress that generally depends on the doping level.…”

“…Two wide bands at approximately 500 cm À 1 and 1225 cm À 1 and another one of low intensity at approximately 1000 cm -1 are added on the low frequency side of the spectrum of the samples grown with higher boron content (samples B-D). These bands are commonly observed in the Raman spectra of polycrystalline and homoepitaxial heavily boron-doped diamond films [14,16], although their origin is still a matter of controversy. The phonon density of states of diamond presents a main asymmetric maximum around 1250 cm À 1 and secondary maximum around 550 cm À 1 and hence their origin has been attributed to the relaxation of selection rules induced by the high boron content [18].…”