The Enchanting Properties of Oxygen Atoms in Silicon

Needels, M.; Joannopoulos, John D.; Bar‐Yam, Yaneer; Pantelides, S. T.; Wolfe, R. H.

doi:10.1557/proc-209-103

Cited by 16 publications

(18 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This barrier corresponds to the two atoms crossing the midpoints of their respective paths at the same time. It could be argued that this configuration constitutes the saddle point, as was assumed in several previous investigations [4][5][6][7][8]. The total barrier of ϳ2.2 eV is indeed in good agreement with the experimental value.…”

supporting

confidence: 89%

“…[8], Needels et al found a value of 1.8 eV and attributed the discrepancy with experiment to dynamical phenomena, i.e., the neighboring Si atoms do not relax fully along the O trajectory. They reported model dynamical calculations for a "generic" nonadiabatic path in which the O atom was given an initial "kick," i.e., an initial velocity corresponding to a kinetic energy of 2.0, 2.3, or 2.7 eV.…”

mentioning

confidence: 99%

“…The resulting total energy, measured from the energy of the equilibrium configuration, represents the adiabatic activation energy for diffusion. Some authors [4,5] reported activation energies around 2.5 eV, while others [6][7][8] reported smaller values ranging from 1.2 to 2.0 eV.…”

mentioning

confidence: 99%

“…4. References [4][5][6][7][8] assumed that the saddle point is at u O u Si 90 ± , shown as a dot in Fig. 4.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Coupled-Barrier Diffusion: The Case of Oxygen in Silicon

Ramamoorthy

Pantelides

1996

Phys. Rev. Lett.

View full text Add to dashboard Cite

Oxygen migration in silicon corresponds to an apparently simple jump between neighboring bridge sites. Yet extensive theoretical calculations have so far produced conflicting results and have failed to provide a satisfactory account of the observed 2.5 eV activation energy. We report a comprehensive set of first-principles calculations that demonstrate that the seemingly simple oxygen jump is actually a complex process involving coupled barriers and can be properly described quantitatively in terms of an energy hypersurface with a "saddle ridge" and an activation energy of ϳ2.5 eV. Earlier calculations correspond to different points or lines on this hypersurface. PACS numbers: 66.30.Jt, 31.15.Ar, 81.60.Cp Oxygen in silicon has long been known to occupy a bridge position between neighboring Si atoms, with an Si-O-Si configuration similar to those in SiO 2 [1,2]. Its diffusion, measured to have an activation energy of 2.5 eV [3], is generally believed to consist of simple jumps between neighboring bridge positions on the (110) plane defined by the corresponding Si-Si bonds ( Fig. 1). In terms of the angle u O defined in Fig. 1, the midpoint of the jump is at u O 90 ± .Most calculations to date [4-8] assumed such a simple adiabatic jump, with reflection symmetry about the vertical axis shown in Fig. 1. Thus, the saddle point was assumed to have the O atom at u O 90 ± and the central Si atom at u Si 90 ± . The remaining degrees of freedom and the positions of the other Si atoms were determined by total-energy minimization. The resulting total energy, measured from the energy of the equilibrium configuration, represents the adiabatic activation energy for diffusion. Some authors [4,5] reported activation energies around 2.5 eV, while others [6-8] reported smaller values ranging from 1.2 to 2.0 eV.In Ref.[8], Needels et al. found a value of 1.8 eV and attributed the discrepancy with experiment to dynamical phenomena, i.e., the neighboring Si atoms do not relax fully along the O trajectory. They reported model dynamical calculations for a "generic" nonadiabatic path in which the O atom was given an initial "kick," i.e., an initial velocity corresponding to a kinetic energy of 2.0, 2.3, or 2.7 eV. They found that when the kick energy was ,2.5 eV, the O atom went past the saddle point but then returned to the original bridge position. When the kick was .2.5 eV the O atom migrated to the next bridge site. They concluded that their results suggested that dynamical effects are important in O migration, but did not constitute definitive evidence.In a recent paper, Jiang and Brown (JB) [9] sought to resolve the issue by exploring the entire migration path. They performed total-energy minimizations by stepping the oxygen atom from one bridge site to the next. They found that the total energy attains a value of only ϳ1.2 eV at u O 90 ± , but then keeps rising to a maximum value (saddle point) of ϳ2.5 eV at u O 113 ± . In addition, they computed the diffusion constant and found it to agree very well with experiment over 12 dec...

show abstract

supporting

confidence: 89%

mentioning

confidence: 99%

mentioning

confidence: 99%

“…4. References [4][5][6][7][8] assumed that the saddle point is at u O u Si 90 ± , shown as a dot in Fig. 4.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Coupled-Barrier Diffusion: The Case of Oxygen in Silicon

Ramamoorthy

Pantelides

1996

Phys. Rev. Lett.

View full text Add to dashboard Cite

show abstract

“…We calculate this energy to be 2.0 eV above its respective BC ground state, consistent w ! ith previous ab initio calculations 6,7 . Therefore, the presence of hydrogen is responsible for at least a 0.54 eV reduction in the saddle-point energy, in excellent agreement with experiments.…”

mentioning

confidence: 66%

"Ab initio" studies of hydrogen-enhanced oxygen diffusion in silicon

et al. 1999

View full text Add to dashboard Cite

A n o vel microscopic mechanism for hydrogen-enhanced oxygen di usion in p-doped silicon is proposed. A path for joint di usion of O and H is obtained from an ab-initio molecular dynamics "kick" simulation. The migration pathway consists of a two-step mechanism, with a maximum energy of 1.46 eV. This path represents a 0.54 eV reduction in the static barrier when compared with the di usion of isolated O in Si, in excellent agreement with experiments.Being the predominant impurity in Czochralskigrown silicon, oxygen has been extensively studied since the early years of semiconductor research 1 . In particular, the di usion of oxygen in silicon is extremely important from a technological point-of-view, since it governs both the formation of electric-active o xygen complexes thermal donors" 2, 3 and the precipitation of SiO 2 in silicon 1 .The ground-state con guration of a single oxygen in silicon is a bent bond-center BC i n terstitial O i . Di usion of O i in silicon occurs by jumps between neighboring BC sites with a measured migration energy of 2.53-2.56 eV 4 . Theoretical calculations 6, 7 have been performed within the framework of transition state theory TST 5 , in which the migration energy is expressed as the energy di erence between two static con gurations: the ground-state and the saddlepoint. For the case of O i , the saddle-point is the wellknown "ylid" con guration, with a three-fold coordinated oxygen. These ab-initio pseudopotential, localdensity-functional, supercell calculations give migration energies in the range of 1.8-2.2 eV. Several mechanisms have been proposed to explain this discrepancy with respect to experimental results 6, 7 , 8 .It has been observed that oxygen di usion in hydrogenated silicon occurs with a much l o wer activation energy, 1.6-2.0 eV 9, 1 0 , 11 . The microscopic mechanism responsible for this enhancement o f o xygen di usion in the presence of hydrogen is still controversial. There are a few theoretical proposals in the literature. Based on Hartree-Fock cluster calculations, Estreicher 12 has proposed that the di usion process would initiate with H in a metastable tetrahedral T site which w ould then assist an oxygen jump to a neighboring bond center with an activation energy of 1.25 eV. During the process, the H atom itself would become trapped in a stable BC con guration. This model assumes that H di usion in silicon is an out-of-equilibrium process on which the hydrogen atoms jump between adjacent T sites, without actually visiting the BC ground-state. This view is not supported by either ab initio 13 or tightbinding ? molecular-dynamics MD simulations of hydrogen di usion. Another proposal is due to Jones et al 15 , based on local-density-functional LDF cluster calculations. In disagreement with Estreicher, they nd the anti-bonding AB site opposite to the Si-O-

show abstract

The Role of Trivalent Oxygen in Electrically Active Complexes

Deák

1996

Early Stages of Oxygen Precipitation in Silicon

View full text Add to dashboard Cite

The Enchanting Properties of Oxygen Atoms in Silicon

Cited by 16 publications

References 29 publications

Coupled-Barrier Diffusion: The Case of Oxygen in Silicon

Coupled-Barrier Diffusion: The Case of Oxygen in Silicon

"Ab initio" studies of hydrogen-enhanced oxygen diffusion in silicon

The Role of Trivalent Oxygen in Electrically Active Complexes

Contact Info

Product

Resources

About