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

A novel microscopic mechanism for hydrogen-enhanced oxygen diffusion in p-doped silicon is proposed. A path for joint diffusion 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 diffusion of isolated O in Si, in excellent agreement with experiments.

Authorship

R. B. Capaz

Universidade Federal do Rio de Janeiro, Instituto de Física , Rio de Janeiro, RJ, BrazilUniversidade Federal do Rio de JaneiroBrazilRio de Janeiro, RJ, BrazilUniversidade Federal do Rio de Janeiro, Instituto de Física , Rio de Janeiro, RJ, Brazil

L. V. C. Assali

Universidade de São Paulo, Instituto de Fí sica , São Paulo, SP, BrazilUniversidade de São PauloBrazilSão Paulo, SP, BrazilUniversidade de São Paulo, Instituto de Fí sica , São Paulo, SP, Brazil

L. C. Kimerling

Massachusetts Institute of Technology, Department of Materials Science and Engineering , Cambridge, MassachusettsMassachusetts Institute of TechnologyCambridge, MassachusettsMassachusetts Institute of Technology, Department of Materials Science and Engineering , Cambridge, Massachusetts

K. Cho

Stanford University, Mechanical Engineering Department , Stanford, CaliforniaStanford UniversityStanford, CaliforniaStanford University, Mechanical Engineering Department , Stanford, California

J. D. Joannopoulos

Massachusetts Institute of Technology, Department of Physics , Cambridge, MassachusettsMassachusetts Institute of TechnologyCambridge, MassachusettsMassachusetts Institute of Technology, Department of Physics , Cambridge, Massachusetts

SCIMAGO INSTITUTIONS RANKINGS

Stanford University, Mechanical Engineering Department , Stanford, CaliforniaStanford UniversityStanford, CaliforniaStanford University, Mechanical Engineering Department , Stanford, California

Figures | Tables

Figures (2)
Tables (1)

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Figure 1.
Geometries and electronic densities of four configurations of the O+H pair in silicon, on the (110) plane which contains both impurities. Atomic positions are represented by the vertices formed the thick lines. Contours run from 0.25 to 6.25 electrons/Å³. (a) Initial ground-state configuration, with BC O and H. The arrow indicates the direction of the initial "kick" on the oxygen. (b) "Saddle-point" configuration, defined as the configuration with maximum potential energy (1.46 eV above the ground state) during the MD simulation. (c) Metastable state with 0.30 eV, with H-saturated Si-Si broken bond. (d) Final "ground-state" configuration, with BC O and H. A true ground-state can be obtained by rotations of H and O along the Si-Si axes.

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Figure 2.
Electronic density for the empty gap state at the metastable configuration. Contours run from 0.02 to 0.10 electrons/Å³.

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Table I.
Some bond lengths and bond angles of the ground- and metastable state configurations of O+H in Si, shown in Fig. 1(a) and 1(c), respectively. Si_c denotes the central Si atom, which is initially bonded to both O and H.

Figure 1. Geometries and electronic densities of four configurations of the O+H pair in silicon, on the (110) plane which contains both impurities. Atomic positions are represented by the vertices formed the thick lines. Contours run from 0.25 to 6.25 electrons/Å³. (a) Initial ground-state configuration, with BC O and H. The arrow indicates the direction of the initial "kick" on the oxygen. (b) "Saddle-point" configuration, defined as the configuration with maximum potential energy (1.46 eV above the ground state) during the MD simulation. (c) Metastable state with 0.30 eV, with H-saturated Si-Si broken bond. (d) Final "ground-state" configuration, with BC O and H. A true ground-state can be obtained by rotations of H and O along the Si-Si axes.

Figure 2. Electronic density for the empty gap state at the metastable configuration. Contours run from 0.02 to 0.10 electrons/Å³.

Table I. Some bond lengths and bond angles of the ground- and metastable state configurations of O+H in Si, shown in Fig. 1(a) and 1(c), respectively. Si_c denotes the central Si atom, which is initially bonded to both O and H.

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

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