title: Direct Observation of Band Structure Modifications in Nanocrystals of CsPbBr3Perovskite.
abstract: We investigate the variation of the bandgap energy of single quantum dots of CsPbBr3inorganic halide perovskite as a function of size and shape and upon embedding within an ensemble. For that purpose, we make use of valence-loss electron spectroscopy with Z-contrast annular dark-field (ADF) imaging in a state-of-the-art low-voltage monochromatic scanning transmission electron microscope. In the experiment, energy absorption is directly mapped onto individual quantum dots, whose dimensions and location are simultaneously measured to the highest precision. In that way, we establish an intimate relation between quantum dot size and even shape and its bandgap energy on a single object level. We explicitly follow the bandgap increase in smaller quantum dots due to quantum confinement and demonstrate that it is predominantly governed by the smallest of the three edges of the cuboidal perovskite dot. We also show the presence of an effective coupling between proximal dots in an ensemble, leading to band structure modification. These unique insights are directly relevant to the development of custom-designed quantum structures and solids which will be realized by purposeful assemblage of individually characterized and selected quantum dots, serving as building blocks.
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST) , AIST Central 5, Tsukuba 305-8565, Japan.
authors.forename: Junhao
authors.initials: J
authors.lastname: Lin
authors.affiliation: Institute of Physics, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Leyre
authors.initials: L
authors.lastname: Gomez
authors.affiliation: Institute of Physics, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Chris
authors.initials: C
authors.lastname: de Weerd
authors.affiliation: Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University , 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Fujiwara
authors.affiliation: Institute of Physics, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands.|Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University , 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Tom
authors.initials: T
authors.lastname: Gregorkiewicz
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST) , AIST Central 5, Tsukuba 305-8565, Japan.
authors.forename: Kazutomo
authors.initials: K
authors.lastname: Suenaga
keywords: CsPbBr3 nanocrystal; Valence-loss EELS; bandgap modification; monochromatic STEM; quantum confinement effect