Consequences of size-effect and spectral inhomogenity on Raman and photoluminescence spectra of a-C:H

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Abstract

The size of crystals in the nanometer regime limits the precision of their location in the inverse space, and hence, the precision of the physical quantities, which are related to the inverse space. This process can be described as multiplication (masking) of the infinite chain with a pulse function, which represents the size of the crystallite. This multiplication leads to a convolution in the inverse space. The broadening below some sizes is larger than the homogeneous spectral broadening in the given crystal. This extra broadening is spectrally inhomogeneous, which is spectacularly demonstrated by the 'hole burning' in non-crystalline condensed matter. The visible photoluminescence of hydrogenated amorphous carbon shows this inhomogeneously broadened feature. The Raman spectrum of graphitic grains should also be interpreted on this basis. The normal Raman D band broadens as a consequence of the broadening of the phonon modes and should be narrower than the G band, which, being a resonant Raman process, is broadened by the separate broadening of the π and the π* energy levels, and the further broadening of the phonon mode, which also broadened the G band. The broader G band is a generally accepted experimental fact.

Original languageEnglish
Pages (from-to)161-167
Number of pages7
JournalDiamond and Related Materials
Volume10
Issue number2
DOIs
Publication statusPublished - Feb 1 2001

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Keywords

  • Photoluminescence
  • Raman scattering
  • Size effect
  • Spectral inhomogenity

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Chemistry(all)
  • Mechanical Engineering
  • Materials Chemistry
  • Electrical and Electronic Engineering

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