Separation of thesp 3 sp 2
Аннотация: Two different types of amorphous carbon films were deposited on Si substrates, with film hardness of 22 GPa and 40 GPa, by pulsed laser evaporation of graphite targets. The x-ray photoemission spectra (XPS) of the C 1s core level in these films shown two components at 284.3\ifmmode\pm\else\textpm\fi{}0.1 eV and 285.2\ifmmode\pm\else\textpm\fi{}0.1 eV, which were identified with the ${\mathit{sp}}^{2}$ and ${\mathit{sp}}^{3}$ hybrids forms of carbon. The ${\mathit{sp}}^{3}$/${\mathit{sp}}^{2}$ concentration ratio deduced from the area of the components had a value of 2/5 for the harder amorphous carbon film and 1/4 for the softer. Upon annealing the harder film at different temperatures, the ${\mathit{sp}}^{3}$/${\mathit{sp}}^{2}$ ratio remained nearly constant up to about 900 K and then decreased until reaching a value of zero above 1100 K. The C 1s core level shifted 0.3\ifmmode\pm\else\textpm\fi{}0.1 eV toward lower binding energy in the films for annealing temperatures above 900 K. This shift was correlated with an increase in the asymmetry of the C 1s XPS spectra and of the density of states at the Fermi level, as observed by ultraviolet photoemission spectroscopy. There was no detectable \ensuremath{\pi} plasmon in the harder films below 900 K, despite the presence of ${\mathit{sp}}^{2}$ atoms and \ensuremath{\pi} bonds at those temperatures. \textcopyright{} 1996 The American Physical Society.
Год издания: 1996
Авторы: J. Dı́az, G. Paolicelli, S. Ferrer, F. Comin
Издательство: American Physical Society
Источник: Physical review. B, Condensed matter
Ключевые слова: Diamond and Carbon-based Materials Research, Metal and Thin Film Mechanics, Ion-surface interactions and analysis
Другие ссылки: Physical review. B, Condensed matter (HTML)
PubMed (HTML)
PubMed (HTML)
Открытый доступ: closed
Том: 54
Выпуск: 11
Страницы: 8064–8069