Berlin 2018 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 22: Optical Analysis of Thin Films (Reflection, Ellipsometry, Raman, IR-DUV Spectroscopy, ...): Session II

DS 22.3: Vortrag

Mittwoch, 14. März 2018, 15:30–15:45, H 0111

Interface states revealed by DFT calculation of reflectance anisotropy spectroscopy: GaP on Si(001) — •Charles Patterson and Pankaj Kumar — School of Physics, Trinity College Dublin, Dublin 2, Ireland

States localized at crystalline interfaces between dielectrics can be probed using optical reflectance anisotropy when the light is incident from the side of the material with the larger band gap. We present first-principles calculations of the anisotropy of the GaP/Si(001) interface [1] and compare them to the interface part of the anisotropy derived from measurements on several GaP thin films on Si(001) with different thickness [2]. The calculations show excellent agreement with experiment only for a gapped interface with a P layer in contact with Si. Interfaces are gapped only when the underlying Si is doped owing to excess electrons in the dimer layer at the GaP surface. Optical excitations from two states localized in several Si layers adjacent to the interface result in the observed anisotropy of the interface. A combination of theory and optical anisotropy experiment can therefore reveal localized electronic states and the atomic structure at buried interfaces.

[1] P. Kumar and C. H. Patterson, Phys. Rev. Lett. 118 237403 (2017) [2] O. Supplie et al., Phys. Rev. B 86, 035308 (2012)