Theory of anharmonicity on bond-centered hydrogen oscillators in silicon

✍ Scribed by J. Coutinho; V.J.B. Torres; R.N. Pereira; B. Bech Nielsen; R. Jones; P.R. Briddon

• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 120 KB
• Volume: 376-377
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2005.12.033

✦ Synopsis

An anomalous positive shift when the mass of the Si host isotope is increased has been observed recently [Pereira et al., Physica B 340-342 (2003) 697] for the asymmetric stretch frequency of the bond-centered proton in Si ðH þ BC Þ. On the other hand, the usual downward isotope shift was observed for the analogous bond-centered deuteron ðD þ BC Þ. Based on phenomenological and ab initio modeling studies, we explain the observed puzzling effect. We introduce a Si-H-Si linear model that accounts well for the observations when anharmonicity, volumetric effects due to the host-isotope mass change, and the coupling of the Si-H-Si unit to the lattice are taken into account. The positive isotope shift for H þ BC results from anharmonic A 2u þ A 1g mode mixing and volumetric effects.