Electronic Structure of Platinum in Silicon

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Abstract
The negatively charged state of substitutional platinum in silicon is observable by electron paramagnetic resonance (EPR). The g-tensor of the EPR spectrum (labelled Si-Pt[I]) reveals orthorhombic-I symmetry of the centre. The principal g-values, which are g[110] = 1.3867, g[10] = 1.4266 and g[001] = 2.0789, respectively, deviate significantly from the pure spin value g = 2.0023, indicating substantial contributions from orbital momentum. The g-tensor data were analysed on a model of one electron, with spin S = 1/2, in an orbital triplet state, L = 1. Spin-orbit coupling and crystal field interactions of cubic, tetragonal or orthorhombic symmetry were included in the model. The theoretical analysis can account in a satisfactory manner for the experimentally observed values. The electronic structure of Pt- is concluded to be the 5d96s6p configuration. This is consistent with predominant bonding of platinum with two silicon neighbours and dihedral distortion. The results are incompatible with alternative models, such as the vacancy model or a 5d-version of the Ludwig-Woodbury model. The orbital g-factor is reduced by about 30% by covalency.