Muonium In Diamond Research Articles

Identification of anomalous muonium in semiconductors as a vacancy-associated center.

With use of a first-principles unrestricted Hartree-Fock cluster procedure, it is demonstrated that a (${\ensuremath{\mu}}^{+}{e}^{\ensuremath{-}}$) center trapped near a vacancy has all the features of the hyperfine tensors for anomalous muonium in diamond and silicon obtained from muon-spin-rotation measurements.

Electronic structure and hyperfine interaction of muonium in semi-conductors

The Unrestricted Hartree-Fock self-consistent field cluster procedure is being utilized for first-principle investigations of the electronic structures and hyperfine interactions in normal and anomalous muonium states in semi-conductors. Our results for the total energy for the normal muonium state for a twenty-seven atom cluster in diamond, including the muonium and its neighboring atoms, show a minimum at the tetrahedral site and a maximum at the hexagonal site indicating that normal muonium is located in the tetrahedral region and avoids the hexagonal region. Using the calculated spin-density as a function of the position of muonium and carrying out averaging over the vibrational motion of the muon governed by the total energy curve obtained from our work, we have derived a muon hyperfine constant which is about 75% of that in free muonium, in good agreement with experiment. The natures of the total energy and spindensity curves permit us to draw conclusions regarding the origin of the observed trend in the hyperfine constants for normal muonium in diamond, silicon and germanium. The UHF cluster procedure is also applied to study a model of a muon in a positively charged environment for the anomalous muonium center in diamond. This model leads to a hyperfine interaction tensor with the observed feature of strong anisotropy but significantly weaker than experiment. The results obtained for this model indicate the importance for the anomalous muonium state with its relatively weak hyperfine interaction, of exchange polarization effects inherent in the UHF procedure.

Self-Consistent-Field Investigation of Location and Hyperfine Interaction of Muonium in Diamond

With use of an unrestricted Hartree-Fock self-consistent-field cluster approach, the potential experienced by a muon in diamond has been investigated. The results strongly indicate that normal muonium is localized in the tetrahedral interstitial space. By using the calculated spin density and averaging it explicitly over the vibrational motion of the muon a quantitative explanation is obtained for the observed reduction of the hyperfine field as compared to free muonium.

Screening of impurities in semiconductors: Muonium in germanium, silicon, and diamond

With the use of the density-functional formalism and the pseudopotential description of the electronic structure of a semiconductor, a new simple theory is derived for calculating the ground-state impurity level for deep donors. It is shown that within well-defined approximations the wave function of the impurity level can be determined self-consistently from a set of equations involving the dielectric function and the pseudopotential of the host lattice. The model, which is further simplified by the replacement of the potential by its spherical average around the impurity, is applied to muonium in diamond, Si, and Ge, and it is shown that the muon zero-point motion is essentially important in calculating the hyperfine frequency. The calculated results are in a qualitative agreement with the experiments.