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Off-Center N and O in Silicon
Published online by Cambridge University Press: 28 February 2011
Abstract
The pseudo Jahn-Teller effect and chemical rebonding are both considered as mechanisms that drive substitutional atoms, such as N in Si, off-center. By use of an effective Hamiltonian technique, impurities forming very deep levels, such as Si:N, are found to be susceptible to off-center displacement by the pseudo Jahn-Teller effect. Using a Hartree-Fock technique, we find two classes of N displacements which depend on the relaxation of the nearest-neighbor Si atom “cage”. For outward relaxation of the four nearest neighbors, the N displaces by 0.05 Å in the [111] direction and retains sp3 bonding; this mechanism appears equivalent to the pseudo Jahn-Teller effect. For inward relaxation of the “cage” by 0.45 Å the N displaces by 0.75 Å in the [111] direction and forms a trigonal sp2 bond; this is a chemical rebonding mechanism. Additional cluster calculations suggest that inward relaxation of the “cage” is likely. Similar calculations for 0 revealed a <100> displacement of approximately 1.1Å.
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- Copyright © Materials Research Society 1986
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