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Author |
Hutter, E.M.; Bladt, E.; Goris, B.; Pietra, F.; van der Bok, J.C.; Boneschanscher, M.P.; de Donega, C.M.; Bals, S.; Vanmaekelbergh, D. |
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Title |
Conformal and atomic characterization of ultrathin CdSe platelets with a helical shape |
Type |
A1 Journal article |
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Year  |
2014 |
Publication |
Nano letters |
Abbreviated Journal |
Nano Lett |
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Volume |
14 |
Issue |
11 |
Pages |
6257-6262 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
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Abstract |
Currently, ultrathin colloidal CdSe semiconductor nanoplatelets (NPLs) with a uniform thickness that is controllable up to the atomic scale can be prepared. The optical properties of these 2D semiconductor systems are the subject of extensive research. Here, we reveal their natural morphology and atomic arrangement. Using cryo-TEM (cryo-transmission electron microscopy), we show that the shape of rectangular NPLs in solution resembles a helix. Fast incorporation of these NPLs in silica preserves and immobilizes their helical shape, which allowed us to perform an in-depth study by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Electron tomography measurements confirm and detail the helical shape of these systems. Additionally, high-resolution HAADF-STEM shows the thickness of the NPLs on the atomic scale and furthermore that these are consistently folded along a ?110? direction. The presence of a silica shell on both the top and bottom surfaces shows that Cd atoms must be accessible for silica precursor (and ligand) molecules on both sides. |
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Place of Publication |
Washington |
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Wos |
000345723800036 |
Publication Date |
2014-10-27 |
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ISSN |
1530-6984 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
12.712 |
Times cited |
43 |
Open Access |
OpenAccess |
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Notes |
Dariusz Mitoraj, Hans Meeldijk, Relinde van Dijk-Moes, and Stephan Zevenhuizen are acknowledged for technical support and help with some experiments. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement no. 291667. The authors acknowledge financial support from FOM and NOW [FOM program Functional NanoParticle Solids (FNPS)]. S.B. acknowledges financial support from European Research Council (ERC Starting Grant #335078- COLOURATOMS). E.B. and B.G. gratefully acknowledge financial support by the Flemish Fund for Scientific Research (FWO Vlaanderen).; ECAS_Sara; (ROMEO:white; preprint:; postprint:restricted 12 months embargo; pdfversion:cannot); |
Approved |
Most recent IF: 12.712; 2014 IF: 13.592 |
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Call Number |
UA @ lucian @ c:irua:122209 |
Serial |
490 |
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Author |
Boneschanscher, M.P.; Evers, W.H.; Geuchies, J.J.; Altantzis, T.; Goris, B.; Rabouw, F.T.; van Rossum, S.A.P.; van der Zant, H.S.J.; Siebbeles, L.D.A.; Van Tendeloo, G.; Swart, I.; Hilhorst, J.; Petukhov, A.V.; Bals, S.; Vanmaekelbergh, D.; |
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Title |
Long-range orientation and atomic attachment of nanocrystals in 2D honeycomb superlattices |
Type |
A1 Journal article |
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Year |
2014 |
Publication |
Science |
Abbreviated Journal |
Science |
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Volume |
344 |
Issue |
6190 |
Pages |
1377-1380 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
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Abstract |
Oriented attachment of synthetic semiconductor nanocrystals is emerging as a route for obtaining new semiconductors that can have Dirac-type electronic bands like graphene, but also strong spin-orbit coupling. The two-dimensional assembly geometry will require both atomic coherence and long-range periodicity of the superlattices. We show how the interfacial self-assembly and oriented attachment of nanocrystals results in two-dimensional (2D) metal chalcogenide semiconductors with a honeycomb superlattice. We present an extensive atomic and nanoscale characterization of these systems using direct imaging and wave scattering methods. The honeycomb superlattices are atomically coherent, and have an octahedral symmetry that is buckled; the nanocrystals occupy two parallel planes. Considerable necking and large-scale atomic motion occurred during the attachment process. |
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Place of Publication |
Washington, D.C. |
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Wos |
000337531700035 |
Publication Date |
2014-05-30 |
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ISSN |
0036-8075;1095-9203; |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
37.205 |
Times cited |
304 |
Open Access |
OpenAccess |
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Notes |
Fwo; 262348 Esmi; 246791 Countatoms; 335078 Colouratom; ECAS_Sara; (ROMEO:green; preprint:; postprint:can ; pdfversion:cannot); |
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Most recent IF: 37.205; 2014 IF: 33.611 |
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Call Number |
UA @ lucian @ c:irua:117095 |
Serial |
1840 |
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Author |
Kalesaki, E.; Boneschanscher, M.P.; Geuchies, J.J.; Delerue, C.; Morais Smith, C.; Evers, W.H.; Allan, G.; Altantzis, T.; Bals, S.; Vanmaekelbergh, D. |
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Title |
Preparation and study of 2-D semiconductors with Dirac type bands due to the honeycomb nanogeometry |
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P1 Proceeding |
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Year |
2014 |
Publication |
Proceedings of the Society of Photo-optical Instrumentation Engineers
T2 – Proceedings of SPIE |
Abbreviated Journal |
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Volume |
8981 |
Issue |
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Pages |
898107-898107 |
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Keywords |
P1 Proceeding; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
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Abstract |
The interest in 2-dimensional systems with a honeycomb lattice and related Dirac-type electronic bands has exceeded the prototype graphene1. Currently, 2-dimensional atomic2,3 and nanoscale4-8 systems are extensively investigated in the search for materials with novel electronic properties that can be tailored by geometry. The immediate question that arises is how to fabricate 2-D semiconductors that have a honeycomb nanogeometry, and as a consequence of that, display a Dirac-type band structure? Here, we show that atomically coherent honeycomb superlattices of rocksalt (PbSe, PbTe) and zincblende (CdSe, CdTe) semiconductors can be obtained by nanocrystal self-assembly and facet-to-facet atomic bonding, and subsequent cation exchange. We present a extended structural analysis of atomically coherent 2-D honeycomb structures that were recently obtained with self-assembly and facet-to-facet bonding9. We show that this process may in principle lead to three different types of honeycomb structures, one with a graphene type-, and two others with a silicene-type structure. Using TEM, electron diffraction, STM and GISAXS it is convincingly shown that the structures are from the silicene-type. In the second part of this work, we describe the electronic structure of graphene-type and silicene type honeycomb semiconductors. We present the results of advanced electronic structure calculations using the sp3d5s* atomistic tight-binding method10. For simplicity, we focus on semiconductors with a simple and single conduction band for the native bulk semiconductor. When the 3-D geometry is changed into 2-D honeycomb, a conduction band structure transformation to two types of Dirac cones, one for S- and one for P-orbitals, is observed. The width of the bands depends on the honeycomb period and the coupling between the nanocrystals. Furthermore, there is a dispersionless P-orbital band, which also forms a landmark of the honeycomb structure. The effects of considerable intrinsic spin-orbit coupling are briefly considered. For heavy-element compounds such as CdTe, strong intrinsic spin-‐orbit coupling opens a non-trivial gap at the P-orbital Dirac point, leading to a quantum Spin Hall effect10-12. Our work shows that well known semiconductor crystals, known for centuries, can lead to systems with entirely new electronic properties, by the simple action of nanogeometry. It can be foreseen that such structures will play a key role in future opto-electronic applications, provided that they can be fabricated in a straightforward way. |
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Wos |
000336040600004 |
Publication Date |
2014-03-07 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
2 |
Open Access |
OpenAccess |
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Notes |
This work has been supported by funding of the French National Research Agency [ANR, (ANR-‐09-‐BLAN-‐0421-‐01)], NWO and the Dutch organization FOM [Programs “Control over Functional Nanoparticle Solids” (FNPS) and “Designing Dirac Carriers in Semiconductors” |
Approved |
Most recent IF: NA |
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Call Number |
c:irua:131912 |
Serial |
4039 |
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