The dynamic motion, within the lattice of single crystal CH3NH3PbBr3 (001) hybrid halide perovskite, was investigated using powder and single crystal x-ray diffraction, and x-ray photoemission spectroscopy. Single crystal x-ray diffraction studies indicate the methylammonium cation adopts multiple orientations within the crystal, at room temperature, evidence of a disordered methylammonium sublattice within a rigid and ordered PbBr3 matrix lattice. From the Br 3d5/2 core level photoemission temperature dependence, an effective Debye temperature of 160 ± 22 K can be estimated, while the Pb 4f7/2 core-level Debye-Waller factor plots suggest an effective Debye temperature of 202 ± 131 K, indicative of a very rigid lattice along the (001) direction. The combination of x-ray diffraction with temperature dependent x-ray photoemission spectroscopy for bromine and lead core level peaks support the characterization of CH3NH3PbBr3 as a lattice polar liquid crystal, as CH3NH3PbBr3 does not meet the criteria required for a ferroelectric material.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The single crystals used in this study were synthesized in the Functional Nanomaterials Lab (FuNL), KAUST. The financial support by King Abdullah University of Science and Technology (KAUST) is acknowledged. The work at the University of Nebraska was supported by the National Science Foundation through the Nebraska MRSEC (Grant No. DMR-1420645), the Nebraska Center for Energy Science and Research. XRD measurements were performed at the Indiana University Nanoscale Characterization Facility. The XRD instrument was funded by NSF award DMR MRI-1126394.