Related Experiment Video
Updated: Sep 12, 2026
Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain
Published on: March 27, 2018
Combinatorial Synthesis of BaCu2Se2 Thin Films: Effect of Composition on Crystal Structure and Optoelectronic
Marin Rusu1, José A Márquez1, Hannes Hempel1
1Department Structure and Dynamics of Energy Materials, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany.
Abstract:
The BaCu2Se2 semiconductor compound with earth-abundant elements is currently studied for application in thermoelectrics. The properties of this emerging material, however, are still not well established, while being mostly investigated on powders or pelletized powders. In this work, BaCu2Se2 thin films are prepared, and the chemical space of Ba-rich and Cu-rich compositions is explored. Ba-Cu-Se thin film combinatorial libraries with lateral compositional gradients with [Cu]/([Ba]+[Cu]) (CBC) atomic ratios between 0.15 and 0.98 are synthesized on areas of 12 × 50 mm2. Using XRF and XRD analysis, composition-resolved phase fractions are determined, which identify the orthorhombic α-BaCu2Se2 as the main phase for CBC between 0.62 and 0.82. Optical measurements reveal for α-BaCu2Se2 a direct bandgap of 1.89 eV and a high absorption coefficient ∼105 cm-1. Surface photovoltage and Seebeck coefficient measurements show p-type conductivity of the films irrespective of composition. Combined Kelvin probe, photoelectron yield, and optical-pump terahertz-probe spectroscopies demonstrate tunability of charge carrier concentrations over several orders of magnitude. The absolute photoluminescence hyperspectral imaging reveals a bright luminescence centered at 1.91 eV and an implied open-circuit voltage of 1.3 eV. Ba-rich conditions are found to be appropriate for the synthesis of films for photovoltaics, while Cu-rich conditions are suitable for the preparation of this material for thermoelectrics.
More Related Videos
Related Concept Videos
02:42Valence Bond Theory
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.