Nature of confinement of phonons in nanocrystalline CVD diamond
2001; Elsevier BV; Volume: 10; Issue: 8 Linguagem: Inglês
10.1016/s0925-9635(00)00616-6
ISSN1879-0062
AutoresAkhilesh Arora, T. R. Ravindran, G.L.N. Reddy, A. K. Sikder, D.S. Misra,
Tópico(s)High-pressure geophysics and materials
ResumoSelf-standing nanocrystalline CVD diamond sheets are investigated using Raman spectroscopy and X-ray diffraction. The sheets are composed of diamond phase and an amorphous-carbon-like non-diamond phase whose content increases with increasing gas pressure in the growth chamber. In the samples synthesised at high pressures the 1332 cm−1 diamond Raman peak exhibits asymmetric broadening. Although the scattering from defects can account for the symmetric part of the line-width, the asymmetry is much more than expected for a confined phonon line-shape calculated according to the Gaussian confinement model for the particle sizes obtained from X-ray diffraction. An alternative model for the confinement of phonons is discussed which involves the standing waves arising from the reflection of the phonons from the elastic-dielectric boundary. The calculated line-shapes arising from the contributions from the allowed q-points in the Brillouin-zone are found to agree with the measured spectra.
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