Regensburg 2019 – wissenschaftliches Programm
KFM 14.7: Poster
Mittwoch, 3. April 2019, 16:00–18:30, Poster C
Polarization dependent vibrational properties of the ferroelectric LiNbO3(0001) surfaces — •Mike Nico Pionteck, Christof Dues, Kris Holtgrewe, and Simone Sanna — Justus-Liebig-Universität Gießen
The investigation of the vibrational properties has recently become one of the most appealing tools for surface analysis. As Raman frequencies as well as selection rules are strongly related to the surface structure, they represent reliable criteria to identify, validate or rule out competing structural models .
In this work, we model the vibrational properties of ferroelectric LiNbO3 surfaces from first principles. The LiNbO3(0001) surfaces are both of technological and academic interest , however, the determination of the polarization direction is usually performed by destructive (chemical etching) or elaborate methods that exploit the pyroelectric or piezoelectric properties of the material. Our calculations reveal the presence of surface localized and polarization specific phonon modes of different symmetry in the frequency range between 30 and 960 cm−1 both at the positive and at the negative LiNbO3(0001) surface. Calculated Raman intensities demonstrate that most of the surface localized modes are Raman active.
Raman spectroscopy can be thus considered as an easier to implement and non-destructive method to determine the polarity of LiNbO3 surfaces.
 B. Halbig et al., Phys. Rev. B 97, 035412 (2018)  S. Sanna et al., J. Phys.: Condens. Matter 29, 413001 (2017)