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Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001)

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Center for nano- and biophotonics (NB-Photonics)
Abstract
In this work, we present a systematic study of the effect of the stoichiometry of BaTiO3 (BTO) films grown on the Ge(001) substrate by molecular-beam-epitaxy using different characterization methods relying on beam diffraction, including reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and selected-area electron diffraction in transmission electron microscopy. Surprisingly, over a wide range of [Ba]/[Ti] ratios, as measured by the Rutherford backscattering spectrometry, all the BTO layers exhibit the same epitaxial relationship < 100 > BTO(001)//< 110 > Ge(001) with the substrate, describing a 45 degrees lattice rotation of the BTO lattice with respect to the Ge lattice. However, varying the [Ba]/[Ti] ratio does change the diffraction behavior. From RHEED patterns, we can derive that excessive [Ba] and [Ti] generate twinning planes and a rougher surface in the non-stoichiometric BTO layers. XRD allows us to follow the evolution of the lattice constants as a function of the [Ba]/[Ti] ratio, providing an option for tuning the tetragonality of the BTO layer. In addition, we found that the intensity ratio of the 3 lowest-order Bragg peaks I-(001)/I-(002), I-(101)/I-(002), and I-(111)/I-(002) derived from omega - 2 theta scans characteristically depend on the BTO stoichiometry. To explain the relation between observed diffraction patterns and the stoichiometry of the BTO films, we propose a model based on diffraction theory explaining how excess [Ba] or [Ti] in the layer influences the diffraction response. Published by AIP Publishing.
Keywords
TITANATE THIN-FILMS, CRYSTALLINE OXIDES, THERMAL-EXPANSION, SILICON, NONSTOICHIOMETRY, DEPOSITION, LAYER

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MLA
Hsu, Min-Hsiang, et al. “Diffraction Studies for Stoichiometry Effects in BaTiO3 Grown by Molecular Beam Epitaxy on Ge(001).” JOURNAL OF APPLIED PHYSICS, vol. 120, no. 22, 2016.
APA
Hsu, M.-H., Merckling, C., El Kazzi, S., Pantouvaki, M., Richard, O., Bender, H., … Van Thourhout, D. (2016). Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001). JOURNAL OF APPLIED PHYSICS, 120(22).
Chicago author-date
Hsu, Min-Hsiang, Clement Merckling, Salim El Kazzi, Marianna Pantouvaki, Oliver Richard, Hugo Bender, Johan Meersschaut, Joris Van Campenhout, Philippe Absil, and Dries Van Thourhout. 2016. “Diffraction Studies for Stoichiometry Effects in BaTiO3 Grown by Molecular Beam Epitaxy on Ge(001).” JOURNAL OF APPLIED PHYSICS 120 (22).
Chicago author-date (all authors)
Hsu, Min-Hsiang, Clement Merckling, Salim El Kazzi, Marianna Pantouvaki, Oliver Richard, Hugo Bender, Johan Meersschaut, Joris Van Campenhout, Philippe Absil, and Dries Van Thourhout. 2016. “Diffraction Studies for Stoichiometry Effects in BaTiO3 Grown by Molecular Beam Epitaxy on Ge(001).” JOURNAL OF APPLIED PHYSICS 120 (22).
Vancouver
1.
Hsu M-H, Merckling C, El Kazzi S, Pantouvaki M, Richard O, Bender H, et al. Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001). JOURNAL OF APPLIED PHYSICS. 2016;120(22).
IEEE
[1]
M.-H. Hsu et al., “Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001),” JOURNAL OF APPLIED PHYSICS, vol. 120, no. 22, 2016.
@article{8627065,
  abstract     = {In this work, we present a systematic study of the effect of the stoichiometry of BaTiO3 (BTO) films grown on the Ge(001) substrate by molecular-beam-epitaxy using different characterization methods relying on beam diffraction, including reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and selected-area electron diffraction in transmission electron microscopy. Surprisingly, over a wide range of [Ba]/[Ti] ratios, as measured by the Rutherford backscattering spectrometry, all the BTO layers exhibit the same epitaxial relationship < 100 > BTO(001)//< 110 > Ge(001) with the substrate, describing a 45 degrees lattice rotation of the BTO lattice with respect to the Ge lattice. However, varying the [Ba]/[Ti] ratio does change the diffraction behavior. From RHEED patterns, we can derive that excessive [Ba] and [Ti] generate twinning planes and a rougher surface in the non-stoichiometric BTO layers. XRD allows us to follow the evolution of the lattice constants as a function of the [Ba]/[Ti] ratio, providing an option for tuning the tetragonality of the BTO layer. In addition, we found that the intensity ratio of the 3 lowest-order Bragg peaks I-(001)/I-(002), I-(101)/I-(002), and I-(111)/I-(002) derived from omega - 2 theta scans characteristically depend on the BTO stoichiometry. To explain the relation between observed diffraction patterns and the stoichiometry of the BTO films, we propose a model based on diffraction theory explaining how excess [Ba] or [Ti] in the layer influences the diffraction response. Published by AIP Publishing.},
  articleno    = {225114},
  author       = {Hsu, Min-Hsiang and Merckling, Clement and El Kazzi, Salim and Pantouvaki, Marianna and Richard, Oliver and Bender, Hugo and Meersschaut, Johan and Van Campenhout, Joris and Absil, Philippe and Van Thourhout, Dries},
  issn         = {0021-8979},
  journal      = {JOURNAL OF APPLIED PHYSICS},
  keywords     = {TITANATE THIN-FILMS,CRYSTALLINE OXIDES,THERMAL-EXPANSION,SILICON,NONSTOICHIOMETRY,DEPOSITION,LAYER},
  language     = {eng},
  number       = {22},
  title        = {Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001)},
  url          = {http://dx.doi.org/10.1063/1.4972101},
  volume       = {120},
  year         = {2016},
}

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