Computational study of interstitial oxygen and vacancy-oxygen complexes in silicon

Abstract

The formation and binding energies, the ionization levels, the structures, and the local vibrations of O i , O 2i , O 3i , VO, VO 2 , and V 2 O (Vϭvacancy͒ in silicon are calculated using a self-consistent total-energy pseudopotential method. The most important results are as follows: The ionization levels and associated structures are given for VO and V 2 O as well as the local vibration modes for the negative charge states of VO.

Vibrations of the Interstitial Oxygen Pairs in Silicon

“…The facts that this frequency agrees closely with the experimental value and in agreement with the experiment shows no 18 O ! 16 O isotopic shift ( Table I) strongly suggest that this LV mode is seen in the experiment at 556 cm 21 . The LV frequencies of the symmetric stretching frequency pair of the skewed O i -Si-Si-O i configuration have not been detected experimentally (see Table I).…”

“…However, improving the accuracy (see Ref. [20]) by increasing the supercell to 128 atom sites and using the G point we find that the latter configuration is by 0.1 eV more stable than the former one [21]. Thus, it is important to consider simultaneously the LV's of both configurations when analyzing the infrared (IR) absorption experiments.…”

“…As to the lower (symmetric stretching-type) LV pairs the calculated upper frequency of the staggered configuration of 697 cm 21 (Table I). Since the corresponding quantities of the skewed O i -Si-Si-O i configuration (643 and 23 cm 21 ) show a less satisfactory agreement the result strongly suggests that the experimental frequency of 690 cm 21 is the upper frequency of the symmetric stretching LV pair of the staggered configuration.…”

Local vibrations of thermal double donors in silicon

“…1͑b͒ and 1͑c͒ resemble those of the staggered dimer. 22,23 The calculated frequency of 987 cm Ϫ1 lies closest to the experimental frequency of 1005 cm Ϫ1 and is thus identified with this ͑Table I͒.…”

“…Therefore, in this case we use an elongated 108-atom-site supercell that gives an intercell distance of 22 Å along the ͓110͔ direction. The procedure and program by Köhler et al 21 used earlier for O i and vacancy-oxygen complexes, [22][23][24] are used in calculating the present LVM's. Every atom vibrating in an LVM is displaced to all six Cartesian directions from its equilibrium position, the electronic structure for this configuration is optimized, and the resulting Hellman-Feynman forces are calculated.…”