First Stage of Oxygen Aggregation in Silicon: The Oxygen Dimer

Abstract

The structure and dynamic properties of the interstitial oxygen dimer in silicon are found using a combination of infrared spectroscopy and ab initio modeling. We find that the stable dimer consists of a pair of inequivalent weakly coupled interstitial oxygen atoms separated by a Si-Si bond. Two high frequency modes are decoupled in one 16 O-18 O combination but are strongly mixed in the other combination. A third lower lying mode involves the compression of the Si-Si bond joining the oxygen atoms and gives distinct modes in the mixed 16 O-18 O case. [S0031-9007(98)07293-7]

Vibrations of the Interstitial Oxygen Pairs in Silicon

“…And, since the symmetric stretching vibration of O i has not been detected because either a linear Si-O i -Si "molecule" is infrared inactive [24] or the amplitude of O i in a puckered case is anyway small [21], it is natural that the symmetric stretching modes of the skewed O i -Si-Si-O i configuration are not detected either. The absence of only the lower frequency of the symmetric stretching frequency pair of the staggered configuration (Table I) Öberg et al [9] using an H-terminated cluster of 88 atoms (44 Si atoms) reported that their calculated frequencies for the skewed O i -Si-Si-O i configuration correlate quite well with the four experimental frequencies while those for their configuration (i)-corresponding to the staggered geometry-do not (Table I). Especially the large mixed 18 O !…”

“…16 O isotopic shift and is characterized as Si related [9]. We find a local oxygen-induced Si mode of this type just above the region of delocalized vibrations Reference [9]. b Reference [8].…”

“…1] [10]. Recently, Öberg et al [9] reported their finding that a skewed O i -Si-Si-O i configuration [two O atoms separated by two Si atoms located in different (110) planes; see Fig. 2] is, in fact, the ground state.…”

“…Murin et al [5] also detected an LV frequency at 1105 cm 21 which they associated with another configuration of O 2i . The subsequent study by Öberg et al [9] using the mixed and pure 18 O ! 16 O isotopes actually proved that the defect giving rise to the four LV frequencies above contains at least two coupled O atoms.…”

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

“…1͑c͒ found by Ö berg et al 44 47 find a slightly bound O 2i . Ö berg et al 44 find that the skewed O i -Si-Si-O i configuration is by 0.14 eV more stable than an O 2i configuration consisting of two neighboring O i 's bound to a common silicon atom, whereas Ewels et al 48 found earlier using the same method that the latter configuration is more stable by 0.68Ϫ0.82 eV. Thus, considerable differences exist between different calculations.…”