Berlin 2012 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 10: High- and low-k-dielectrics (jointly with DS)

DF 10.6: Vortrag

Mittwoch, 28. März 2012, 11:10–11:30, EB 407

Hydrogen Impurity in Y₂O₃: an Ab−Initio and a µSR perspective — •Estelina L. Silva, Apostolos Marinopoulos, Rui Vilão, and Ricardo Vieira — CEMDRX and CFC, Physics Department, University of Coimbra, P-3004-516 Coimbra, Portugal

Density functional calculations were performed for interstitial hydrogen in Y₂O₃, by employing the semi-local GGA-PBE and the hybrid HSE06 exchange-correlation functionals. It was observed that the lowest energy H⁰ and H⁻ configurations prefer to relax in the interstitial, vacant O, sites. For these charge systems, two different geometrical configurations (interstitial vacant Y and bond O-H type) also occur as higher-energy metastable sites. In contrast, the H⁺ equilibrium state was found only when a O-H bond is formed. The overall results for the formation energies, obtained by employing the two functionals are consistent, for which amphoteric behavior was found for hydrogen after considering the lowest-energy structures for each charge state. To compare results with µSR measurements, the formation energies of the metastable configurations were also evaluated. The results are consistent with the µSR data, where the co-existence of the observed diamagnetic signal is attributed to a shallow donor-like muonium and the paramagnetic signal to an acceptor-like deep muonium configuration.

For the interstitial configurations, of the neutral and negative charge systems, a defect level was found in the gap and positioned slightly above the valence band maximum, whereas for the bond O-H site, the defect level is located above the middle of the band gap, closer to the conduction band.