title: Coexistence of Two Electronic Nano-Phases on a CH3NH3PbI3-xClxSurface Observed in STM Measurements.
abstract: Scanning tunneling microscopy is utilized to investigate the local density of states of a CH3NH3PbI3-xClxperovskite in cross-sectional geometry. Two electronic phases, 10-20 nm in size, with different electronic properties inside the CH3NH3PbI3-xClxperovskite layer are observed by the dI/dV mapping and point spectra. A power law dependence of the dI/dV point spectra is revealed. In addition, the distinct electronic phases are found to have preferential orientations close to the normal direction of the film surface. Density functional theory calculations indicate that the observed electronic phases are associated with local deviation of I/Cl ratio, rather than different orientations of the electric dipole moments in the ferroelectric phases. By comparing the calculated results with experimental data we conclude that phase A (lower contrast in dI/dV mapping at -2.0 V bias) contains a lower I/Cl ratio than that in phase B (higher contrast in dI/dV).
authors.affiliation: Department of Physics and Astronomy, University of Wyoming , Laramie, Wyoming 82071, United States.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Yost
authors.affiliation: Department of Physics and Astronomy, University of Wyoming , Laramie, Wyoming 82071, United States.
authors.forename: Artem
authors.initials: A
authors.lastname: Pimachev
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University , Taipei 10617, Taiwan.|Center for Nanoscale Materials, Argonne National Laboratory , Lemont, Illinois 60439, United States.
authors.forename: Chun-Chih
authors.initials: CC
authors.lastname: Ho
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory , Lemont, Illinois 60439, United States.|Institute for Molecular Engineering, University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: Seth B
authors.initials: SB
authors.lastname: Darling
authors.affiliation: Center for Condensed Matter Sciences, National Taiwan University , Taipei 10617, Taiwan.
authors.forename: Leeyih
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University , Taipei 10617, Taiwan.
authors.forename: Wei-Fang
authors.initials: WF
authors.lastname: Su
authors.affiliation: Department of Physics and Astronomy, University of Wyoming , Laramie, Wyoming 82071, United States.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Dahnovsky
authors.affiliation: Department of Physics and Astronomy, University of Wyoming , Laramie, Wyoming 82071, United States.
authors.forename: TeYu
authors.initials: T
authors.lastname: Chien
keywords: cross-sectional scanning tunneling microscopy; density functional theory; electronic phase; mixed halide; nano-phase; organometallic halide perovskite