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Proceedings Paper

Critical-point phonons of diamond
Author(s): Claude A. Klein; Thomas M. Hartnett; Clifford J. Robinson
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Paper Abstract

The phono-dispersion curves derived from neutron-scattering experiments performed on diamond are not accurate enough to yield the exact frequencies of critical-point (CP) phonons and, thus, to provide a satisfactory interpretation of second-order optical spectra. A self- consistent analysis of such spectra proved to be difficult because it is not a straightforward task to assign second-order absorption and scatter features to specific two-phonon summations. A more effective method for obtaining accurate CP-phonon frequencies involves investigating defect-activated one-phonon absorptions; in this paper, the authors take advantage of the availability of chemically vapor-deposited (CVD) diamond for the purpose of locating and assigning infrared (IR) absorption features in the one-phonon region to CP phonons at the Brillouin-zone boundary. Fourier-transform IR absorbance spectra of CVD diamond exhibit a complex structure at wavenumbers below the 1333-cm-1 band-mode cutoff, which is induced by nitrogen-associated defect centers and yields the precise positions of sixteen zone-edge CP phonons. In conjunction with the triply-degenerate zone-center mode, this set of phonons then provides the basis for predicting the positions of second-order optical features through simple summations. Taking the selection rules into account, the procedure yields excellent results, not only in terms of CVD-diamond IR spectra, but also in regard to earlier measurements of the intrinsic two-phonon absorption coefficient of type-IIa natural diamond and the second-order polarization-dependent Raman-scatter characteristics recorded by Solin and Ramdas.

Paper Details

Date Published: 1 December 1991
PDF: 22 pages
Proc. SPIE 1534, Diamond Optics IV, (1 December 1991); doi: 10.1117/12.48285
Show Author Affiliations
Claude A. Klein, Raytheon Co. (United States)
Thomas M. Hartnett, Raytheon Co. (United States)
Clifford J. Robinson, Raytheon Co. (United States)

Published in SPIE Proceedings Vol. 1534:
Diamond Optics IV
Albert Feldman; Sandor Holly, Editor(s)

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