Nanocrystals in motion: in-situ study of consecutive phase transitions in the formation of atomically coherent two-dimensional superlattices from PbSe nanocrystals

Joep Peters^a, Jaco Geuchies^a, Freddy Rabouw^a, Anjan Gantapara^a, Carlo Van Overbeek^a, Daniel Vanmaekelbergh^a, Marjolein Dijkstra^a, Laurens Siebbeles^b, Wiel Evers^b, Sandra Van Aert^c, Sara Bals^c, Bart Goris^c, Annick De Backer^c, Jan Hilhorst^d, Oleg Konovalov^d, Andrei Petukhov^e

^aDelft University of Technology, The Netherlands, Julianalaan, 136, Delft, Netherlands

^bElectron Microscopy for Materials Science, University of Antwerp, Belgium

^cEuropean Synchrotron Radiation Facility (ESRF), 71 Avenue des Martyrs, Grenoble, France

^dLaboratory of Physical Chemistry, Eindhoven University of Technology, Building 14, Helix, Eindhoven, Netherlands

Materials for Sustainable Development Conference (MATSUS)
Proceedings of September Meeting 2016 (NFM16)

Berlin, Germany, 2016 September 5th - 13th

Organizers: Marin Alexe, Enrique Cánovas, Celso de Mello Donega, Ivan Infante, Thomas Kirchartz, Maksym Kovalenko, Federico Rosei, Lukas Schmidt-Mende, Laurens Siebbeles, Peter Strasser, Teodor K Todorov, Roel van de Krol and Ulrike Woggon

Oral, Jaco Geuchies, presentation 301
Publication date: 14th June 2016

The formation of atomically coherent 2-D PbSe superstructures from nanocubic building blocks can result in long-range atomic and nanoscale order [1,2]. This order questions classic models [3] in which the superlattice grows by sequential irreversible attachment of nanocrystals, since one “wrong” attachment would disrupt the 2-D order beyond repair. We have studied the mechanism of the formation of 2-D PbSe superstructures with square geometry using in-situ grazing-incidence x-ray scattering (small-angle and wide-angle), ex-situ electron microscopy, and Monte Carlo simulations. The nanocrystals adsorb at the liquid-gas interface, followed by the formation of a hexagonal nanocrystal monolayer. As time progresses, the hexagonal layer is deformed to a square superlattice, due to the four-fold symmetry of the in-plane interaction caused by the PbSe nanocrystal facets. During these consecutive phase transitions the nanocrystals align themselves atomically and finally form atomic bonds.

[1] Evers, W.H. et al. Low-dimensional semiconductor superlattices formed by geometric control over nanocrystal attachment. Nano Lett. 13, 2317-23 (2013).

[2] Boneschanscher, M. P. et al. Long-range orientation and atomic attachments of nanocrystals in 2D honeycomb superlattices. Science(80-). science. 1252642-(2014). doi: 10.1126/science.1252642.

[3] Poung, G.M. & Mer, V.K. La. Kinetics of Crystalline Nucleus Formation in Supercooled Liquid Tin 1.2. J. Am. Chem. Soc. 74, 2323-2332 (1952).

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