@article{40444,
  author       = {{von Bardeleben, H. J. and Rauls, E. and Gerstmann, Uwe}},
  issn         = {{2469-9950}},
  journal      = {{Physical Review B}},
  number       = {{18}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Carbon vacancy-related centers in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>3</mml:mn><mml:mi>C</mml:mi></mml:math>-silicon carbide: Negative-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>U</mml:mi></mml:math> properties and structural transformation}}},
  doi          = {{10.1103/physrevb.101.184108}},
  volume       = {{101}},
  year         = {{2020}},
}

@article{22887,
  author       = {{Vondran, J. and Spitzer, F. and Bayer, M. and Akimov, I. A. and Trautmann, Alexander and Reichelt, Matthias and Meier, Cedrik and Weber, N. and Meier, Torsten and André, R. and Mariette, H.}},
  issn         = {{2469-9950}},
  journal      = {{Physical Review B}},
  number       = {{15}},
  pages        = {{155308}},
  title        = {{{Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure}}},
  doi          = {{10.1103/physrevb.100.155308}},
  volume       = {{100}},
  year         = {{2019}},
}

@article{13410,
  author       = {{Friedrich, Michael and Schmidt, Wolf Gero and Schindlmayr, Arno and Sanna, Simone}},
  issn         = {{2475-9953}},
  journal      = {{Physical Review Materials}},
  number       = {{1}},
  publisher    = {{American Physical Society}},
  title        = {{{Erratum: Optical properties of titanium-doped lithium niobate from time-dependent density-functional theory [Phys. Rev. Materials 1, 034401 (2017)]}}},
  doi          = {{10.1103/PhysRevMaterials.2.019902}},
  volume       = {{2}},
  year         = {{2018}},
}

@article{3434,
  abstract     = {{In this work we study the impact of ion implantation on the nonlinear optical properties in MgO:LiNbO3 via confocal second-harmonic microscopy. In detail, we spatially characterize the nonlinear susceptibility in carbon-ion implanted lithium niobate planar waveguides for different implantation energies and fluences, as well as the effect of annealing. In a further step, a computational simulation is used to calculate the implantation range of carbon-ions and the corresponding defect density distribution. A comparison between the simulation and the experimental data indicates that the depth profile of the second-order effective nonlinear coefficient is directly connected to the defect density that is induced by the ion irradiation. Furthermore it can be demonstrated that the annealing treatment partially recovers the second-order optical susceptibility.}},
  author       = {{Spychala, Kai J. and Berth, Gerhard and Widhalm, Alex and Rüsing, Michael and Wang, Lei and Sanna, Simone and Zrenner, Artur}},
  issn         = {{1094-4087}},
  journal      = {{OPTICS EXPRESS}},
  number       = {{18}},
  pages        = {{21444----21453}},
  title        = {{{Impact of carbon-ion implantation on the nonlinear optical susceptibility of LiNbO3}}},
  doi          = {{10.1364/OE.25.021444}},
  year         = {{2017}},
}

@article{10021,
  abstract     = {{The optical properties of pristine and titanium-doped LiNbO3 are modeled from first principles. The dielectric functions are calculated within time-dependent density-functional theory, and a model long-range contribution is employed for the exchange-correlation kernel in order to account for the electron-hole binding. Our study focuses on the influence of substitutional titanium atoms on lithium sites. We show that an increasing titanium concentration enhances the values of the refractive indices and the reflectivity.}},
  author       = {{Friedrich, Michael and Schmidt, Wolf Gero and Schindlmayr, Arno and Sanna, Simone}},
  issn         = {{2475-9953}},
  journal      = {{Physical Review Materials}},
  number       = {{3}},
  publisher    = {{American Physical Society}},
  title        = {{{Optical properties of titanium-doped lithium niobate from time-dependent density-functional theory}}},
  doi          = {{10.1103/PhysRevMaterials.1.034401}},
  volume       = {{1}},
  year         = {{2017}},
}

@article{13416,
  abstract     = {{The optical properties of congruent lithium niobate are analyzed from first principles. The dielectric function of the material is calculated within time-dependent density-functional theory. The effects of isolated intrinsic defects and defect pairs, including the NbLi4+ antisite and the NbLi4+−NbNb4+ pair, commonly addressed as a bound polaron and bipolaron, respectively, are discussed in detail. In addition, we present further possible realizations of polaronic and bipolaronic systems. The absorption feature around 1.64 eV, ascribed to small bound polarons [O. F. Schirmer et al., J. Phys.: Condens. Matter 21, 123201 (2009)], is nicely reproduced within these models. Among the investigated defects, we find that the presence of bipolarons at bound interstitial-vacancy pairs NbV−VLi can best explain the experimentally observed broad absorption band at 2.5 eV. Our results provide a microscopic model for the observed optical spectra and suggest that, besides NbLi antisites and Nb and Li vacancies, Nb interstitials are also formed in congruent lithium-niobate samples.}},
  author       = {{Friedrich, Michael and Schmidt, Wolf Gero and Schindlmayr, Arno and Sanna, Simone}},
  issn         = {{2475-9953}},
  journal      = {{Physical Review Materials}},
  number       = {{5}},
  publisher    = {{American Physical Society}},
  title        = {{{Polaron optical absorption in congruent lithium niobate from time-dependent density-functional theory}}},
  doi          = {{10.1103/PhysRevMaterials.1.054406}},
  volume       = {{1}},
  year         = {{2017}},
}

@article{4239,
  abstract     = {{Confocal Raman spectroscopy is applied to identify ferroelectric domain structure sensitive
phonon modes in potassium titanyl phosphate. Therefore, polarization-dependent measurements in
various scattering configurations have been performed to characterize the fundamental Raman
spectra of the material. The obtained spectra are discussed qualitatively based on an internal mode
assignment. In the main part of this work, we have characterized z-cut periodically poled potassium
titanyl phosphate in terms of polarity- and structure-sensitive phonon modes. Here, we find vibrations
whose intensities are linked to the ferroelectric domain walls. We interpret this in terms of
changes in the polarizability originating from strain induced by domain boundaries and the inner
field distribution. Hence, a direct and 3D visualization of ferroelectric domain structures becomes
possible in potassium titanyl phosphate.}},
  author       = {{Rüsing, Michael and Eigner, Christof and Mackwitz, P. and Berth, Gerhard and Silberhorn, Christine and Zrenner, Artur}},
  issn         = {{0021-8979}},
  journal      = {{Journal of Applied Physics}},
  number       = {{4}},
  publisher    = {{AIP Publishing}},
  title        = {{{Identification of ferroelectric domain structure sensitive phonon modes in potassium titanyl phosphate: A fundamental study}}},
  doi          = {{10.1063/1.4940964}},
  volume       = {{119}},
  year         = {{2016}},
}

@article{4237,
  abstract     = {{We report the fabrication of periodically poled domain patterns in x-cut lithium niobate thin-film.
Here, thin films on insulator have drawn particular attention due to their intrinsic waveguiding
properties offering high mode confinement and smaller devices compared to in-diffused waveguides
in bulk material. In contrast to z-cut thin film lithium niobate, the x-cut geometry does not
require back electrodes for poling. Further, the x-cut geometry grants direct access to the largest
nonlinear and electro-optical tensor element, which overall promises smaller devices. The domain
inversion was realized via electric field poling utilizing deposited aluminum top electrodes on a
stack of LN thin film/SiO2 layer/Bulk LN, which were patterned by optical lithography. The periodic
domain inversion was verified by non-invasive confocal second harmonic microscopy. Our
results show domain patterns in accordance to the electrode mask layout. The second harmonic signatures
can be interpreted in terms of spatially, overlapping domain filaments which start their
growth on the þz side.}},
  author       = {{Mackwitz, P. and Rüsing, Michael and Berth, Gerhard and Widhalm, A. and Müller, K. and Zrenner, Artur}},
  issn         = {{0003-6951}},
  journal      = {{Applied Physics Letters}},
  number       = {{15}},
  publisher    = {{AIP Publishing}},
  title        = {{{Periodic domain inversion in x-cut single-crystal lithium niobate thin film}}},
  doi          = {{10.1063/1.4946010}},
  volume       = {{108}},
  year         = {{2016}},
}

@article{4240,
  abstract     = {{Cubic gallium nitride (GaN) films are analyzed with highresolution X-ray diffraction (HRXRD) and Raman spectroscopy. Several cubic GaN layers were grown on 3C-SiC (001) substrate by radio-frequency plasma-assisted molecular beam epitaxy. The layer thickness of the cubic GaN was varied between 75 and 505 nm. The HRXRD analysis reveals a reduction of the full-width at half-maximum (FWHM) of omega scans for growing layer thicknesses, which is caused by a partial compensation of defects. The Raman characterization confirms well-formed c-GaN layers. A more detailed examination of the longitudinal optical mode hints at a correlation of the FWHM of the Raman mode with the dislocation density, which shows the possibility to determine dislocation densities by Ramanspectroscopy on a micrometer scale, which is not possible by HRXRD. Furthermore, this Raman analysis shows that normalized Raman spectra present an alternative way to determine layer thicknesses of thin GaN films.}},
  author       = {{Rüsing, Michael and Wecker, T. and Berth, Gerhard and As, Donat Josef and Zrenner, Artur}},
  issn         = {{0370-1972}},
  journal      = {{physica status solidi (b)}},
  keywords     = {{cubic gallium nitride, dislocation density, HRXRD, Raman spectroscopy}},
  number       = {{4}},
  pages        = {{778--782}},
  publisher    = {{Wiley}},
  title        = {{{Joint Raman spectroscopy and HRXRD investigation of cubic gallium nitride layers grown on 3C-SiC}}},
  doi          = {{10.1002/pssb.201552592}},
  volume       = {{253}},
  year         = {{2016}},
}

@article{10026,
  abstract     = {{Congruent lithium niobate and lithium tantalate mixed crystals have been grown over the complete
compositional range with the Czochralski method. The structural and vibrational properties of the mixed
crystals are studied extensively by x-ray diffraction measurements, Raman spectroscopy, and density functional
theory. The measured lattice parameters and vibrational frequencies are in good agreement with our theoretical
predictions. The observed dependence of the Raman frequencies on the crystal composition is discussed on the
basis of the calculated phonon displacement patterns. The phononic contribution to the static dielectric tensor
is calculated by means of the generalized Lyddane-Sachs-Teller relation. Due to the pronounced dependence of
the optical response on the Ta concentration, lithium niobate tantalate mixed crystals represent a perfect model
system to study the properties of uniaxial mixed ferroelectric materials for application in integrated optics.}},
  author       = {{Rüsing, Michael and Sanna, Simone and Neufeld, Sergej and Berth, Gerhard and Schmidt, Wolf Gero and Zrenner, Artur and Yu, H. and Wang, Y. and Zhang, H.}},
  issn         = {{2469-9950}},
  journal      = {{Physical Review B}},
  title        = {{{Vibrational properties of LiNb1−xTaxO3 mixed crystals}}},
  doi          = {{10.1103/physrevb.93.184305}},
  year         = {{2016}},
}

@article{4332,
  abstract     = {{LiTaO3 and LiNbO3 crystals are investigated here in a combined experimental and theoretical study that uses Raman spectroscopy in a complete set of scattering geometries and corresponding density-functional theory calculations to provide microscopic information on their vibrational properties. The Raman scattering efficiency is computed from first principles in order to univocally assign the measured Raman peaks to the calculated eigenvectors. Measured and calculated Raman spectra are shown to be in qualitative agreement and confirm the mode assignment by Margueron et al. [J. Appl. Phys. 111, 104105 (2012)], thus finally settling a long debate. While the two crystals show rather similar vibrational properties overall, the E-TO9 mode is markedly different in the two oxides. The deviations are explained by a different anion-cation bond type in LiTaO3 and LiNbO3 crystals.}},
  author       = {{Sanna, Simone and Neufeld, Sergej and Rüsing, Michael and Berth, Gerhard and Zrenner, Artur and Schmidt, Wolf Gero}},
  issn         = {{1098-0121}},
  journal      = {{Physical Review B}},
  number       = {{22}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Raman scattering efficiency in LiTaO3 and LiNbO3 crystals}}},
  doi          = {{10.1103/physrevb.91.224302}},
  volume       = {{91}},
  year         = {{2015}},
}

@article{13504,
  author       = {{Sanna, S. and Dues, C. and Schmidt, Wolf Gero}},
  issn         = {{0927-0256}},
  journal      = {{Computational Materials Science}},
  pages        = {{145--150}},
  title        = {{{Modeling atomic force microscopy at LiNbO 3 surfaces from first-principles}}},
  doi          = {{10.1016/j.commatsci.2015.03.025}},
  volume       = {{103}},
  year         = {{2015}},
}

@article{13506,
  author       = {{Sanson, A. and Zaltron, A. and Argiolas, N. and Sada, C. and Bazzan, M. and Schmidt, Wolf Gero and Sanna, S.}},
  issn         = {{1098-0121}},
  journal      = {{Physical Review B}},
  title        = {{{Polaronic deformation at theFe2+/3+impurity site inFe:LiNbO3crystals}}},
  doi          = {{10.1103/physrevb.91.094109}},
  volume       = {{91}},
  year         = {{2015}},
}

@article{13515,
  author       = {{Sanna, S. and Hölscher, R. and Schmidt, Wolf Gero}},
  issn         = {{0169-4332}},
  journal      = {{Applied Surface Science}},
  pages        = {{70--78}},
  title        = {{{Temperature dependent LiNbO3(0001): Surface reconstruction and surface charge}}},
  doi          = {{10.1016/j.apsusc.2014.01.104}},
  year         = {{2014}},
}