1. Diffraction studies for stoichiometry effects in BaTiO3 grown by molecular beam epitaxy on Ge(001).
- Author
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Hsu, Min-Hsiang Mark, Merckling, Clement, El Kazzi, Salim, Pantouvaki, Marianna, Richard, Oliver, Bender, Hugo, Meersschaut, Johan, Van Campenhout, Joris, Absil, Philippe, and Van Thourhout, Dries
- Subjects
X-ray diffraction ,HIGH energy electron diffraction ,STOICHIOMETRY ,THIN films ,MOLECULAR beam epitaxy ,TRANSMISSION electron microscopy - Abstract
In this work, we present a systematic study of the effect of the stoichiometry of BaTiO
3 (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 h100iBTO(001)// 〈110〉Ge(001) with the substrate, describing a 45° 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 ω-2θ 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. [ABSTRACT FROM AUTHOR]- Published
- 2016
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