Huge isotope effect on the vibrational lifetimes of an H2*(C) defect in Si

Autor: K. Potter, Michael Stavola, Figen Bekisli, T. M. Gibbons, Stefan K. Estreicher
Rok vydání: 2013
Předmět:
Zdroj: Physical Review B. 87
ISSN: 1550-235X
1098-0121
DOI: 10.1103/physrevb.87.115207
Popis: The hydrogenation of C-rich Si leads to the formation of two (almost) energetically degenerate ${\mathrm{H}}_{2}^{*}(\mathrm{C})$ complexes, each containing one substitutional C (${\mathrm{C}}_{\mathrm{s}}$) and two interstitial H atoms which are located at a bond-centered (bc) and an antibonding (ab) site, respectively. The two defects are trigonal: ${\mathrm{C}}_{\mathrm{s}}\ensuremath{-}{\mathrm{H}}_{\mathrm{bc}}\ensuremath{\cdots}\mathrm{Si}\ensuremath{-}{\mathrm{H}}_{\mathrm{ab}}$ and ${\mathrm{H}}_{\mathrm{ab}}\ensuremath{-}{\mathrm{C}}_{\mathrm{s}}\ensuremath{\cdots}{\mathrm{H}}_{\mathrm{bc}}\ensuremath{-}\mathrm{Si}$. Fourier-transform infrared (FTIR) absorption spectra of these two defects should show two ${\mathrm{C}}_{\mathrm{s}}\ensuremath{-}\mathrm{H}$ and two $\mathrm{Si}\ensuremath{-}\mathrm{H}$ stretch modes, but the ${\mathrm{H}}_{\mathrm{ab}}\ensuremath{-}{\mathrm{C}}_{\mathrm{s}}$ mode was absent in earlier studies. The missing line has now been observed by FTIR in especially C rich Si material. The line is unexpectedly broad, suggesting a very short vibrational lifetime. Partial D substitutions result in the formation of a ${\mathrm{H}}_{\mathrm{ab}}\ensuremath{-}{\mathrm{C}}_{\mathrm{s}}\ensuremath{\cdots}{\mathrm{D}}_{\mathrm{bc}}\ensuremath{-}\mathrm{Si}$ center. In this defect, the ${\mathrm{H}}_{\mathrm{ab}}\ensuremath{-}{\mathrm{C}}_{\mathrm{s}}$ line shifts by only $0.3\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ but becomes very sharp, suggesting a long lifetime. The IR line widths show that the vibrational lifetime of the ${\mathrm{H}}_{\mathrm{ab}}\ensuremath{-}{\mathrm{C}}_{\mathrm{s}}$ mode in ${\mathrm{H}}_{\mathrm{ab}}\ensuremath{-}{\mathrm{C}}_{\mathrm{s}}\ensuremath{\cdots}{\mathrm{D}}_{\mathrm{bc}}\ensuremath{-}\mathrm{Si}$ is about 16 times longer than that of the same ${\mathrm{H}}_{\mathrm{ab}}\ensuremath{-}{\mathrm{C}}_{\mathrm{s}}$ mode in ${\mathrm{H}}_{\mathrm{ab}}\ensuremath{-}{\mathrm{C}}_{\mathrm{s}}\ensuremath{\cdots}{\mathrm{H}}_{\mathrm{bc}}\ensuremath{-}\mathrm{Si}$. This paper contains experimental data and first-principles calculations which explain this isotope effect.
Databáze: OpenAIRE