TY - JOUR
T1 - Lattice isotope effects on optical transitions in silicon
AU - Hayama, S.
AU - Davies, G.
AU - Tan, J.
AU - Coutinho, J.
AU - Jones, R.
AU - Itoh, K. M.
N1 - Funding Information:
The work in London was supported by EPSRC Grant Nos. GR/R10820 and GR/R24531/01, and in Keio it was partly supported by a Grant-in-Aid for Scientific Research in Priority Area “Semiconductor Nanospintronics (No. 14076215).” J.T. thanks the K.C. Wong Foundation and the China Scholarship Council for financial support.
PY - 2004/7
Y1 - 2004/7
N2 - We report the changes with lattice isotope of the energies of the zero-phonon lines (ZPLs) and some of the local vibrational modes (LVMs) of commonly encountered radiation-damage centers in silicon. On changing from natSi to 30Si, ZPLs of the different centers shift by +0.8 to +1.8 meV. The carbon-oxygen "C" center is taken as the primary example. For this center, the measured changes in the frequencies of the LVMs in the electronic ground state of the center agree closely with the results of density functional theory (DFT). We suggest that the LVM frequencies in the excited state can be obtained from DFT calculations of the positive charge state. The effect on the ZPL is broken into three parts. The dependence of the ZPL on the isotopically induced change in the LVMs and in the lattice volume is shown to be small compared to the effects of the electron-phonon coupling to the continuum of lattice modes. This dominant effect can be found, in principle, from the temperature dependence of the energy of the ZPL, but data can only be measured over too small a temperature range. We suggest that an estimate of the isotope effects can be derived by rescaling the appropriate data for the indirect energy gap. This simple empirical approach reproduces the measured isotope shifts of the ZPLs of the "C" and "P" centers within ∼10%, of the "I" and "T" centers within ∼30%, and within a factor of 2 for the "G" center.
AB - We report the changes with lattice isotope of the energies of the zero-phonon lines (ZPLs) and some of the local vibrational modes (LVMs) of commonly encountered radiation-damage centers in silicon. On changing from natSi to 30Si, ZPLs of the different centers shift by +0.8 to +1.8 meV. The carbon-oxygen "C" center is taken as the primary example. For this center, the measured changes in the frequencies of the LVMs in the electronic ground state of the center agree closely with the results of density functional theory (DFT). We suggest that the LVM frequencies in the excited state can be obtained from DFT calculations of the positive charge state. The effect on the ZPL is broken into three parts. The dependence of the ZPL on the isotopically induced change in the LVMs and in the lattice volume is shown to be small compared to the effects of the electron-phonon coupling to the continuum of lattice modes. This dominant effect can be found, in principle, from the temperature dependence of the energy of the ZPL, but data can only be measured over too small a temperature range. We suggest that an estimate of the isotope effects can be derived by rescaling the appropriate data for the indirect energy gap. This simple empirical approach reproduces the measured isotope shifts of the ZPLs of the "C" and "P" centers within ∼10%, of the "I" and "T" centers within ∼30%, and within a factor of 2 for the "G" center.
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U2 - 10.1103/PhysRevB.70.035202
DO - 10.1103/PhysRevB.70.035202
M3 - Article
AN - SCOPUS:42749108107
VL - 70
SP - 035202-1-035202-9
JO - Physical Review B-Condensed Matter
JF - Physical Review B-Condensed Matter
SN - 1098-0121
IS - 3
M1 - 035202
ER -