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Lookup NU author(s): Richard Jones,
Professor Patrick Briddon
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Infrared absorption measurements on n-type silicon doped with carbon and irradiated with electrons at room temperature have revealed new absorption lines at 527.4 and 748.7 cm(-1), which originate from the same defect. The 748.7-cm(-1) line is observed only when the sample is cooled in the dark and the spectrum is measured through a low-pass filter with cutoff frequency below 6000 cm(-1). Light with frequency above 6000 cm(-1) removes this line and generates the 527.4-cm(-1) line. Comparison with spectra recorded on irradiated cm silicon doped with C-13 shows that the two lines represent local vibrational modes of carbon. The annealing behavior of the 748.7-cm(-1) line is identical to that of the EPR signal originating from the negative charge state of two adjacent substitutional carbon atoms (C-s-C-s)(-). The 527.4- and 748.7-cm(-1) lines are ascribed to the E modes of C-s-C-s in the neutral and negative charge states, respectively. The structure and local vibrational modes of (C-s-C-s)(0) and (C-s-C-s)(-) have been calculated by ab initio local density functional theory. The calculated structures agree qualitatively with those obtained previously by Hartree-Fock methods, but the calculated Si-C and C-C bond lengths differ somewhat. The calculated local mode frequencies are in good agreement with those observed. The formation of C-s-C-s has also been investigated. It is suggested that the center is formed when a vacancy is trapped by the metastable substitutional carbon-interstitial carbon center, C-s-C-i.
Author(s): Lavrov EV, Nielsen BB, Byberg JR, Hourahine B, Jones R, Oberg S, Briddon PR
Publication type: Article
Publication status: Published
Journal: Physical Review B
ISSN (print): 0163-1829
ISSN (electronic): 0556-2805
Publisher: American Physical Society
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