Collective topo-epitaxy in the self-assembly of a 3D quantum dot superlattice

Alex Abelson; Caroline Qian; Trenton Salk; Zhongyue Luan; Kan Fu; Jian-Guo Zheng; Jenna L Wardini; Matt Law

doi:10.1038/s41563-019-0485-2

Collective topo-epitaxy in the self-assembly of a 3D quantum dot superlattice

Nat Mater. 2020 Jan;19(1):49-55. doi: 10.1038/s41563-019-0485-2. Epub 2019 Oct 14.

Authors

Alex Abelson^#¹, Caroline Qian^#², Trenton Salk³, Zhongyue Luan¹, Kan Fu¹, Jian-Guo Zheng⁴, Jenna L Wardini¹, Matt Law^{5

6

7}

Affiliations

¹ Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA, USA.
² Department of Chemical and Biomolecular Engineering, University of California, Irvine, Irvine, CA, USA.
³ Department of Physics and Astronomy, University of California, Irvine, Irvine, CA, USA.
⁴ Irvine Materials Research Institute, University of California, Irvine, Irvine, CA, USA.
⁵ Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA, USA. matt.law@uci.edu.
⁶ Department of Chemical and Biomolecular Engineering, University of California, Irvine, Irvine, CA, USA. matt.law@uci.edu.
⁷ Department of Chemistry, University of California, Irvine, Irvine, CA, USA. matt.law@uci.edu.

^# Contributed equally.

PMID: 31611669
DOI: 10.1038/s41563-019-0485-2

Abstract

Epitaxially fused colloidal quantum dot (QD) superlattices (epi-SLs) may enable a new class of semiconductors that combine the size-tunable photophysics of QDs with bulk-like electronic performance, but progress is hindered by a poor understanding of epi-SL formation and surface chemistry. Here we use X-ray scattering and correlative electron imaging and diffraction of individual SL grains to determine the formation mechanism of three-dimensional PbSe QD epi-SL films. We show that the epi-SL forms from a rhombohedrally distorted body centred cubic parent SL via a phase transition in which the QDs translate with minimal rotation (~10°) and epitaxially fuse across their {100} facets in three dimensions. This collective epitaxial transformation is atomically topotactic across the 10³-10⁵ QDs in each SL grain. Infilling the epi-SLs with alumina by atomic layer deposition greatly changes their electrical properties without affecting the superlattice structure. Our work establishes the formation mechanism of three-dimensional QD epi-SLs and illustrates the critical importance of surface chemistry to charge transport in these materials.