title: An intrinsic growth instability in isotropic materials leads to quasi-two-dimensional nanoplatelets.
abstract: Colloidal nanoplatelets are atomically flat, quasi-two-dimensional sheets of semiconductor that can exhibit efficient, spectrally pure fluorescence. Despite intense interest in their properties, the mechanism behind their highly anisotropic shape and precise atomic-scale thickness remains unclear, and even counter-intuitive for commonly studied nanoplatelets that arise from isotropic crystal structures (such as zincblende CdSe and lead halide perovskites). Here we show that an intrinsic instability in growth kinetics can lead to such highly anisotropic shapes. By combining experimental results on the synthesis of CdSe nanoplatelets with theory predicting enhanced growth on narrow surface facets, we develop a model that explains nanoplatelet formation as well as observed dependencies on time and temperature. Based on standard concepts of volume, surface and edge energies, the resulting growth instability criterion can be directly applied to other crystalline materials. Thus, knowledge of this previously unknown mechanism for controlling shape at the nanoscale can lead to broader libraries of quasi-two-dimensional materials.
authors.affiliation: Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Riedinger
authors.affiliation: Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Florian D
authors.initials: FD
authors.lastname: Ott
authors.affiliation: Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Aniket
authors.initials: A
authors.lastname: Mule
authors.affiliation: Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Sergio
authors.initials: S
authors.lastname: Mazzotti
authors.affiliation: Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Philippe N
authors.identifier: 0000-0002-9546-5809
authors.initials: PN
authors.lastname: Knüsel
authors.affiliation: Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Stephan J P
authors.initials: SJP
authors.lastname: Kress
authors.affiliation: Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Ferry
authors.initials: F
authors.lastname: Prins
authors.affiliation: Center for Computational Materials Science, Naval Research Laboratory, Washington DC 20375, USA.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Erwin
authors.affiliation: Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: David J
authors.initials: DJ
authors.lastname: Norris