Dresden 2014 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 58: Emerging oxide semiconductors I (Focus session with DS)
HL 58.3: Talk
Wednesday, April 2, 2014, 10:15–10:30, POT 081
Intrinsic point defects in Cu2O - Lifting of Raman selection rules — •Thomas Sander, Christian T. Reindl, and Peter J. Klar — I. Physikalisches Institut, Justus-Liebig-Universität Gießen
The copper oxide system Cu2O receives currently a renewed interest due to its potential photovoltaic applications. Its natural p-type conductivity is due to intrinsic defects. Understanding the formation and properties of such point defects is of major relevance for tuning the material for optoelectronic applications.
Crystalline cubic Cu2O exhibits a very unusual feature which is up to now unexplained in the literature. Instead of showing just one optical mode expected for cubic symmetry, Raman spectra of Cu2O are dominated by Raman forbidden phonons independent of the method used for growth. A group theoretical analysis will be presented showing that the forbidden phonons will become Raman allowed when the symmetry is lowered due to the formation of point defects. Furthermore, it will be shown that of all possible intrinsic defects the copper split vacancies cause the lifting of the Raman selection rules. The results are experimentally confirmed by making use of the full angle and polarization dependence called rotational Raman spectroscopy (RoRa). Low temperature Raman studies further reveal that the degeneracy of phonon modes is lifted which is in accordance with the results of the group theoretical analysis.
Thus the detailed Raman study of Cu2O in combination with the group theoretical analysis yields much more insight than just a proof of selection rules or identification of lattice modes.