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

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.

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Fig. 1: Fabrication and ligand chemistry of PbSe QD epi-SLs.
Fig. 2: Structure of the oleate-capped QD SL films.
Fig. 3: Structure of the epi-SL films.
Fig. 4: The phase transition pathway.
Fig. 5: Effect of ALD alumina infilling on the epi-SLs.

Data availability

The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.

References

  1. 1.

    Boles, M. A., Engel, M. & Talapin, D. V. Self-assembly of colloidal nanocrystals: from intricate structures to functional materials. Chem. Rev. 116, 11220–11289 (2016).

    CAS  Google Scholar 

  2. 2.

    Lazarenkova, O. L. & Balandin, A. A. Miniband formation in a quantum dot crystal. J. Appl. Phys. 89, 5509–5515 (2001).

    CAS  Google Scholar 

  3. 3.

    Jiang, C.-W. & Green, M. A. Silicon quantum dot superlattices: modeling of energy bands, densities of states, and mobilities for silicon tandem solar cell applications. J. Appl. Phys. 99, 114902 (2006).

    Google Scholar 

  4. 4.

    Whitham, K. et al. Charge transport and localization in atomically coherent quantum dot solids. Nat. Mater. 15, 557–563 (2016).

    CAS  Google Scholar 

  5. 5.

    Gómez-Campos, F. M., Rodríguez-Bolívar, S. & Califano, M. High-mobility toolkit for quantum dot films. ACS Photon. 3, 2059–2067 (2016).

    Google Scholar 

  6. 6.

    Guyot-Sionnest, P. Electrical transport in colloidal quantum dot films. J. Phys. Chem. Lett. 3, 1169–1175 (2012).

    CAS  Google Scholar 

  7. 7.

    Liu, Y. et al. PbSe quantum dot field-effect transistors with air-stable electron mobilities above 7 cm2 V–1 s–1. Nano Lett. 13, 1578–1587 (2013).

    CAS  Google Scholar 

  8. 8.

    Kagan, C. R. & Murray, C. B. Charge transport in strongly coupled quantum dot solids. Nat. Nanotechnol. 10, 1013–1026 (2015).

    CAS  Google Scholar 

  9. 9.

    Evers, W. H. et al. High charge mobility in two-dimensional percolative networks of PbSe quantum dots connected by atomic bonds. Nat. Commun. 6, 8195 (2015).

    CAS  Google Scholar 

  10. 10.

    Evers, W. H. et al. Low-dimensional semiconductor superlattices formed by geometric control over nanocrystal attachment. Nano Lett. 13, 2317–2323 (2013).

    CAS  Google Scholar 

  11. 11.

    Baumgardner, W. J., Whitham, K. & Hanrath, T. Confined-but-connected quantum solids via controlled ligand displacement. Nano Lett. 13, 3225–3231 (2013).

    CAS  Google Scholar 

  12. 12.

    Dong, A., Chen, J., Vora, P. M., Kikkawa, J. M. & Murray, C. B. Binary nanocrystal superlattice membranes self-assembled at the liquid–air interface. Nature 466, 474–477 (2010).

    CAS  Google Scholar 

  13. 13.

    Dong, A., Jiao, Y. & Milliron, D. J. Electronically coupled nanocrystal superlattice films by in situ ligand exchange at the liquid–air interface. ACS Nano 7, 10978–10984 (2013).

    CAS  Google Scholar 

  14. 14.

    Sandeep, C. S. S. et al. Epitaxially connected PbSe quantum-dot films: controlled neck formation and optoelectronic properties. ACS Nano 8, 11499–11511 (2014).

    CAS  Google Scholar 

  15. 15.

    Boneschanscher, M. P. et al. Long-range orientation and atomic attachment of nanocrystals in 2D honeycomb superlattices. Science 344, 1377–1380 (2014).

    CAS  Google Scholar 

  16. 16.

    Zhao, M. et al. High hole mobility in long-range ordered 2D lead sulfide nanocrystal monolayer films. Adv. Funct. Mater. 26, 5182–5188 (2016).

    CAS  Google Scholar 

  17. 17.

    Geuchies, J. J. et al. In situ study of the formation mechanism of two-dimensional superlattices from PbSe nanocrystals. Nat. Mater. 15, 1248–1254 (2016).

    CAS  Google Scholar 

  18. 18.

    Walravens, W. et al. Chemically triggered formation of two-dimensional epitaxial quantum dot superlattices. ACS Nano 10, 6861–6870 (2016).

    CAS  Google Scholar 

  19. 19.

    Zhao, M. et al. Ligand effects on electronic and optoelectronic properties of two-dimensional PbS necking percolative superlattices. Nano Res. 10, 1249–1257 (2017).

    CAS  Google Scholar 

  20. 20.

    Treml, B. E. et al. Successive ionic layer absorption and reaction for postassembly control over inorganic interdot bonds in long-range ordered nanocrystal films. ACS Appl. Mater. Interfaces 9, 13500–13507 (2017).

    CAS  Google Scholar 

  21. 21.

    Balazs, D. M. et al. Electron mobility of 24 cm2 V–1 s–1 in PbSe colloidal-quantum-dot superlattices. Adv. Mater. 30, 1802265 (2018).

    Google Scholar 

  22. 22.

    van Overbeek, C. et al. Interfacial self-assembly and oriented attachment in the family of PbX (X = S, Se, Te) nanocrystals. J. Phys. Chem. C 122, 12464–12473 (2018).

    Google Scholar 

  23. 23.

    Savitzky, B. H. et al. Propagation of structural disorder in epitaxially connected quantum dot solids from atomic to micron scale. Nano Lett. 16, 5714–5718 (2016).

    CAS  Google Scholar 

  24. 24.

    Whitham, K. & Hanrath, T. Formation of epitaxially connected quantum dot solids: nucleation and coherent phase transition. J. Phys. Chem. Lett. 8, 2623–2628 (2017).

    CAS  Google Scholar 

  25. 25.

    Peters, J. L. et al. Mono- and multilayer silicene-type honeycomb lattices by oriented attachment of PbSe nanocrystals: synthesis, structural characterization, and analysis of the disorder. Chem. Mater. 30, 4831–4837 (2018).

    CAS  Google Scholar 

  26. 26.

    Shannon, R. D. & Rossi, R. C. Definition of topotaxy. Nature 202, 1000–1001 (1964).

    Google Scholar 

  27. 27.

    Son, D. H., Hughes, S. M., Yin, Y. & Alivisatos, A. P. Cation exchange reactions in ionic nanocrystals. Science 306, 1009–1012 (2004).

    CAS  Google Scholar 

  28. 28.

    Macfarlane, R. J., Jones, M. R., Lee, B., Auyeung, E. & Mirkin, C. A. Topotactic interconversion of nanoparticle superlattices. Science 341, 1222–1225 (2013).

    CAS  Google Scholar 

  29. 29.

    Rossi, R. C. & Fulrath, R. M. Epitaxial growth of spinel by reaction in the solid state. J. Am. Ceram. Soc. 46, 145 (1963).

    CAS  Google Scholar 

  30. 30.

    Wang, Y. et al. Dynamic deformability of individual PbSe nanocrystals during superlattice phase transitions. Sci. Adv. 5, eaaw5623 (2019).

    Google Scholar 

  31. 31.

    Bealing, C. R., Baumgardner, W. J., Choi, J. J., Hanrath, T. & Hennig, R. G. Predicting nanocrystal shape through consideration of surface–ligand interactions. ACS Nano 6, 2118–2127 (2012).

    CAS  Google Scholar 

  32. 32.

    Ning, Z. et al. Air-stable n-type colloidal quantum dot solids. Nat. Mater. 13, 822–828 (2014).

    CAS  Google Scholar 

  33. 33.

    Brown, P. R. et al. Energy level modification in lead sulfide quantum dot thin films through ligand exchange. ACS Nano 8, 5863–5872 (2014).

    CAS  Google Scholar 

  34. 34.

    Harris, R. D. et al. Electronic processes within quantum dot–molecule complexes. Chem. Rev. 116, 12865–12919 (2016).

    CAS  Google Scholar 

  35. 35.

    Law, M. et al. Structural, optical, and electrical properties of PbSe nanocrystal solids treated thermally or with simple amines. J. Am. Chem. Soc. 130, 5974–5985 (2008).

    CAS  Google Scholar 

  36. 36.

    Anderson, N. C., Hendricks, M. P., Choi, J. J. & Owen, J. S. Ligand exchange and the stoichiometry of metal chalcogenide nanocrystals: spectroscopic observation of facile metal–carboxylate displacement and binding. J. Am. Chem. Soc. 135, 18536–18548 (2013).

    CAS  Google Scholar 

  37. 37.

    Choi, J. J. et al. Controlling nanocrystal superlattice symmetry and shape-anisotropic interactions through variable ligand surface coverage. J. Am. Chem. Soc. 133, 3131–3138 (2011).

    CAS  Google Scholar 

  38. 38.

    Weidman, M. C., Smilgies, D.-M. & Tisdale, W. A. Kinetics of the self-assembly of nanocrystal superlattices measured by real-time in situ X-ray scattering. Nat. Mater. 15, 775–781 (2016).

    CAS  Google Scholar 

  39. 39.

    Bian, K. et al. Shape-anisotropy driven symmetry transformations in nanocrystal superlattice polymorphs. ACS Nano 4, 2815–2823 (2011).

    Google Scholar 

  40. 40.

    Simon, P. et al. PbS–organic mesocrystals: the relationship between nanocrystal orientation and superlattice array. Angew. Chem. Int. Ed. 51, 10776–10781 (2012).

    CAS  Google Scholar 

  41. 41.

    Santra, P. K., Palmstrom, A. F., Tassone, C. J. & Bent, S. F. Molecular ligands control superlattice structure and crystallite orientation in colloidal quantum dot solids. Chem. Mater. 28, 7072–7081 (2016).

    CAS  Google Scholar 

  42. 42.

    Novák, J. et al. Site-specific ligand interactions favor the tetragonal distortion of PbS nanocrystal superlattices. ACS Appl. Mater. Interfaces 8, 22526–22533 (2016).

    Google Scholar 

  43. 43.

    Li, R., Bian, K., Hanrath, T., Bassett, W. A. & Wang, Z. Decoding the superlattice and interface structure of truncate PbS nanocrystal-assembled supercrystal and associated interaction forces. J. Am. Chem. Soc. 136, 12047–12055 (2017).

    Google Scholar 

  44. 44.

    Bian, K., Li, R. & Fan, H. Controlled self-assembly and tuning of large PbS nanoparticle supercrystals. Chem. Mater. 30, 6788–6793 (2018).

    CAS  Google Scholar 

  45. 45.

    Fan, Z. & Grünwald, M. Orientational order in self-assembled nanocrystal superlattices. J. Am. Chem. Soc. 141, 1980–1988 (2019).

    CAS  Google Scholar 

  46. 46.

    Liu, Y. et al. Robust, functional nanocrystal solids by infilling with atomic layer deposition. Nano Lett. 11, 5349–5355 (2011).

    CAS  Google Scholar 

  47. 47.

    Koh, W. K. et al. Heavily doped n-type PbSe and PbS nanocrystals using ground-state charge transfer from cobaltocene. Sci. Rep. 3, 2004 (2013).

    Google Scholar 

  48. 48.

    Araujo, J. J., Brozek, C. K., Kroupa, D. M. & Gamelin, D. R. Degenerately n-doped colloidal PbSe quantum dots: band assignments and electrostatic effects. Nano Lett. 18, 3893–3900 (2018).

    CAS  Google Scholar 

  49. 49.

    Moreels, I. et al. Composition and size-dependent extinction coefficient of colloidal PbSe quantum dots. Chem. Mater. 19, 6101–6106 (2007).

    CAS  Google Scholar 

  50. 50.

    Ilavsky, J. Nika: software for two-dimensional data reduction. J. Appl. Cryst. 45, 324–328 (2012).

    CAS  Google Scholar 

  51. 51.

    Kline, S. R. Reduction and analysis of SANS and USANS data using IGOR Pro. J. Appl. Cryst. 39, 895–900 (2006).

    CAS  Google Scholar 

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Acknowledgements

This work was supported by the UC Office of the President under the UC Laboratory Fees Research Program Collaborative Research and Training Award LFR-17-477148. We thank C. Zhu, E. Schaible and A. Liebman-Pelaez for training and assistance on Beamline 7.3.3 of the Advanced Light Source, T. Aoki for TEM assistance, Q. Lin for X-ray diffraction assistance and D. Smilgies for the use of his GISAXS software and useful correspondence. This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. Materials characterization was performed at the user facilities of the UC Irvine Materials Research Institute, which include instrumentation funded in part by the National Science Foundation Major Research Instrumentation Program under grant no. CHE-1338173.

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Correspondence to Matt Law.

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Supplementary Methods, Figs. 1–23, Tables 1–6 and references.

Supplementary Video S1

Phase transition from an oleate-capped to epitaxially fused colloidal quantum dot superlattice

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Abelson, A., Qian, C., Salk, T. et al. Collective topo-epitaxy in the self-assembly of a 3D quantum dot superlattice. Nat. Mater. 19, 49–55 (2020). https://doi.org/10.1038/s41563-019-0485-2

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