Electronic properties and hyperfine parameters of gold–3d-transition-metal impurity pairs in silicon

Abstract

We report theoretical investigations of the chemical trends in the electronic properties of transition-metal impurity pair complexes in a semiconductor. Self-consistent spin-unrestricted electronic state calculations, with a scalar relativistic scheme, in the framework of the multiple-scattering X␣ molecular cluster method, have been carried out for the substitutional gold-3d interstitial transition-metal pairs in silicon in C 3v symmetry. The role played by the 5d and 3d states of the transition metals in the formation of the impurity energy levels in the crystal band gap and resonances is established. The analysis of the one-electron energy spectra of the impurities leads to the conclusion that the electronic, magnetic, and optical properties of the series can be explained by a simple microscopic model. The calculations do not provide support for the ionic model, where these pairs are described as two point charges electrostatically bounded with a strong magnetic coupling between their spins. Instead, the results lead to a model in which the covalent effects are invoked to explain the chemical trends and the physical properties of the complexes. This model is substantiated by comparing the hyperfine parameters and transition energies with electron paramagnetic resonance and optical experimental data. ͓S0163-1829͑98͒08031-X͔

3d transition metal impurities in diamond: electronic properties and chemical trends

“…Figure 1(a) presents the specific case of Mn i in the neutral charge state (3d 7 ). For other TM i impurities in diamond (from Sc to Cu), their t 2 and e levels have an equivalent behavior to those of Mn i , but with a chemical trend such that those levels move all together from the midgap region, in Sc i , toward the valence band, in Cu i , consistent with results for TM i impurities in other semiconductors 25,26 . The 3d-character localization in the TM atomic spheres increases with increasing the atomic number.…”

3dtransition metal impurities in diamond: Electronic properties and chemical trends

“…We have also shown that trends on transition energies, for any of the three sites, could only be rationalized if they were discussed in terms of the increasing occupation of 3d-related states in the bandgap. Such trends are consistent with what would be expected for transition metal impurities in other semiconductors in either isolated configurations 29,30 or forming complexes with other defects 25,31 . Fig.…”

Electronic properties and hyperfine fields of nickel-related complexes in diamond

“…For the (Ni s N s ) 0 complex, there is a hybridization between 3d-related gap states of Ni s with those 2p-related ones of N s . This indicates a typical covalent interaction between those two impurities 31,32 . Despite this hybridization, the highest occupied energy level in the (Ni s N s ) 0 complex has an e representation, with a prevailing 3d character.…”

“…This indicates a typical covalent interaction between those two impurities. 35 Despite this hybridization, the highest occupied energy level in the ͑Ni s N s ͒ 0 complex has an e representation, with a prevailing 3d character. On the other hand, for the ͑Ni i N s ͒ 0 complex, the electronic structure results from a weaker interaction between the states of the isolated impurities, more consistent with an ionic model.…”