High quality CVD diamond: a Raman scattering and photoluminescence study |
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Authors: | MG Donato G Faggio M Marinelli G Messina E Milani A Paoletti S Santangelo A Tucciarone G Verona Rinati |
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Institution: | (1) INFM, Dipartimento di Meccanica e Materiali, Facoltà di Ingegneria dell'Università, Località Feo di Vito, 89060 Reggio Calabria, Italy, IT;(2) INFM, Dipartimento di Scienze e Tecnologie Fisiche ed Energetiche, Università di Roma Tor Vergata, via di Tor Vergata, 00133 Roma, Italy, IT |
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Abstract: | High quality synthetic diamonds were grown on single-crystal silicon by microwave plasma enhanced chemical vapour deposition
(CVD). A careful optimisation of both the experimental setup and the growth parameters was necessary before that the achievement
of the best results was made possible. The films were deposited using a CH4-H2 gas mixture at methane concentrations variable in the range 0.6-2.2%, while the substrate temperature was fixed at 750 °C. Raman spectroscopy and photoluminescence (PL) were utilised to monitor the quality of the deposited films and to study
the spatial distribution of defects, respectively. Micro-Raman analysis shows that linewidths of the diamond peak lower than
2.4 cm-1 can be easily measured at the growth surface, indicating that the crystalline quality of individual grains is comparable
to that of the best natural diamonds. The excellent phase purity of the diamond microcrystals at the growth surface is witnessed
by the complete absence of any non-diamond carbon feature and by a very weak luminescence background in the 1.6-2.4 eV spectral
range. A worsening of the quality of the diamond particles is found moving from the growth surface towards the film-substrate
interface. A photoluminescence feature at about 1.68 eV, commonly associated to Si impurities, is distinctly observed as the
exciting laser beam is focused close to the interface. A progressive degradation of the global quality of the films is found
with increasing methane concentration in the gas mixture, as witnessed by an increased PL background in the films grown at
higher methane concentrations.
Received 24 November 2000 |
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Keywords: | PACS 81 05 Uw Carbon diamond graphite – 78 30 Am Elemental semiconductors and insulators – 78 55 Ap Elemental semiconductors |
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