1
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Polyanskiy MN. Refractiveindex.info database of optical constants. Sci Data 2024; 11:94. [PMID: 38238330 PMCID: PMC10796781 DOI: 10.1038/s41597-023-02898-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 12/27/2023] [Indexed: 01/22/2024] Open
Abstract
We introduce the refractiveindex.info database, a comprehensive open-source repository containing optical constants for a wide array of materials, and describe in detail the underlying dataset. This collection, derived from a meticulous compilation of data sourced from peer-reviewed publications, manufacturers' datasheets, and authoritative texts, aims to advance research in optics and photonics. The data is stored using a YAML-based format, ensuring integrity, consistency, and ease of access. Each record is accompanied by detailed metadata, facilitating a comprehensive understanding and efficient utilization of the data. In this descriptor, we outline the data curation protocols and the file format used for data records, and briefly demonstrate how the data can be organized in a user-friendly fashion akin to the books in a traditional library.
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Affiliation(s)
- Mikhail N Polyanskiy
- Brookhaven National Laboratory, Accelerator Test Facility, Upton, NY, 11973, USA.
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2
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Salzmann BV, Vliem JF, Maaskant DN, Post LC, Li C, Bals S, Vanmaekelbergh D. From CdSe Nanoplatelets to Quantum Rings by Thermochemical Edge Reconfiguration. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2021; 33:6853-6859. [PMID: 34552306 PMCID: PMC8444342 DOI: 10.1021/acs.chemmater.1c01618] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 08/11/2021] [Indexed: 05/28/2023]
Abstract
The variation in the shape of colloidal semiconductor nanocrystals (NCs) remains intriguing. This interest goes beyond crystallography as the shape of the NC determines its energy levels and optoelectronic properties. While thermodynamic arguments point to a few or just a single shape(s), terminated by the most stable crystal facets, a remarkable variation in NC shape has been reported for many different compounds. For instance, for the well-studied case of CdSe, close-to-spherical quantum dots, rods, two-dimensional nanoplatelets, and quantum rings have been reported. Here, we report how two-dimensional CdSe nanoplatelets reshape into quantum rings. We monitor the reshaping in real time by combining atomically resolved structural characterization with optical absorption and photoluminescence spectroscopy. We observe that CdSe units leave the vertical sides of the edges and recrystallize on the top and bottom edges of the nanoplatelets, resulting in a thickening of the rims. The formation of a central hole, rendering the shape into a ring, only occurs at a more elevated temperature.
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Affiliation(s)
- Bastiaan
B. V. Salzmann
- Condensed
Matter & Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508TA Utrecht, The Netherlands
| | - Jara F. Vliem
- Condensed
Matter & Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508TA Utrecht, The Netherlands
| | - D. Nicolette Maaskant
- Condensed
Matter & Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508TA Utrecht, The Netherlands
| | - L. Christiaan Post
- Condensed
Matter & Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508TA Utrecht, The Netherlands
| | - Chen Li
- EMAT
and Nanolab Centre of Excellence, Antwerp
University, 2020 Antwerp, Belgium
| | - Sara Bals
- EMAT
and Nanolab Centre of Excellence, Antwerp
University, 2020 Antwerp, Belgium
| | - Daniel Vanmaekelbergh
- Condensed
Matter & Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508TA Utrecht, The Netherlands
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3
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Quick MT, Owschimikow N, Achtstein AW. Terahertz Charge Carrier Mobility in 1D and 2D Semiconductor Nanoparticles. J Phys Chem Lett 2021; 12:7688-7695. [PMID: 34378384 DOI: 10.1021/acs.jpclett.1c02045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We investigate the charge carrier mobility in 1D and 2D semiconductor nanoparticle domains with a focus on the interpretation of THz mobility measurements. We provide a microscopic understanding of the frequency-dependent charge carrier transport in these structures of finite lateral size. Yet unexplored oscillations in the frequency-dependent complex conductivity and a strong size dependence of the mobility are observed. The quantum nature of the charge carrier states results in oscillations in the frequency-dependent mobility for subresonant THz probing, seen in experiments. The effect is based on the lack of an energy continuum for the charge motion. In 2D systems the mobility is further governed by transitions in the two orthogonal x- and y-directions and depends nontrivially on the THz polarization, as well as the quantum well lateral aspect ratio, defining the energetic detuning of the lowest THz-photon transitions in both directions. We analyze the frequency, length, and effective mass dependencies.
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Affiliation(s)
- Michael T Quick
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Nina Owschimikow
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Alexander W Achtstein
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
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4
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Greenwood AR, Mazzotti S, Norris DJ, Galli G. Determining the Structure-Property Relationships of Quasi-Two-Dimensional Semiconductor Nanoplatelets. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:4820-4827. [PMID: 38230251 PMCID: PMC10788900 DOI: 10.1021/acs.jpcc.0c10559] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/18/2024]
Abstract
We report a theoretical study of CdSe nanoplatelets aimed at identifying the main factors determining their photophysical properties. Using atomic configurations optimized with density functional theory calculations, we computed quasiparticle and exciton binding energies of nanoplatelets with two to seven monolayers. We employed many body perturbation theory at the GW level and solved the Bethe-Salpeter equation to obtain absorption spectra and excitonic properties. Our results, which agree well with recent experiments, were then used to design a model that allows us to disentangle the effects of quantum confinement, strain induced by passivating ligands, and dielectric environment on the electronic properties of nanoplatelets. We found that, for the model to accurately reproduce our first principle results, it is critical to account for surface stress and consider a finite potential barrier and energy-dependent effective masses when describing quantum confinement. Our findings call into question previous assumptions on the validity of an infinite barrier to describe carrier confinement in nanoplatelets, suggesting that it may be possible to optimize interfacial charge transfer and extraction by appropriately choosing passivating ligands. The model developed here is generalizable to core-shell platelets and enables the description of system sizes not yet directly treatable by first-principles calculations.
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Affiliation(s)
- Arin R. Greenwood
- Pritzker
School of Molecular Engineering, University
of Chicago, Chicago, Illinois 60637, United States
| | - Sergio Mazzotti
- Optical
Materials Engineering Laboratory, Department of Mechanical and Process
Engineering, ETH Zurich, Zurich 8092, Switzerland
| | - David J. Norris
- Optical
Materials Engineering Laboratory, Department of Mechanical and Process
Engineering, ETH Zurich, Zurich 8092, Switzerland
| | - Giulia Galli
- Pritzker
School of Molecular Engineering, University
of Chicago, Chicago, Illinois 60637, United States
- Department
of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
- Argonne
National Laboratory, Argonne, Illinois 60439, United States
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5
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Ayari S, Quick MT, Owschimikow N, Christodoulou S, Bertrand GHV, Artemyev M, Moreels I, Woggon U, Jaziri S, Achtstein AW. Tuning trion binding energy and oscillator strength in a laterally finite 2D system: CdSe nanoplatelets as a model system for trion properties. NANOSCALE 2020; 12:14448-14458. [PMID: 32618327 DOI: 10.1039/d0nr03170d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We present a theoretical study combined with experimental validations demonstrating that CdSe nanoplatelets are a model system to investigate the tunability of trions and excitons in laterally finite 2D semiconductors. Our results show that the trion binding energy can be tuned from 36 meV to 18 meV with the lateral size and decreasing aspect ratio, while the oscillator strength ratio of trions to excitons decreases. In contrast to conventional quantum dots, the trion oscillator strength in a nanoplatelet at low temperature is smaller than that of the exciton. The trion and exciton Bohr radii become lateral size tunable, e.g. from ∼3.5 to 4.8 nm for the trion. We show that dielectric screening has strong impact on these properties. By theoretical modeling of transition energies, binding energies and oscillator strength of trions and excitons and comparison with experimental findings, we demonstrate that these properties are lateral size and aspect ratio tunable and can be engineered by dielectric confinement, allowing to suppress e.g. detrimental trion emission in devices. Our results strongly impact further in-depth studies, as the demonstrated lateral size tunable trion and exciton manifold is expected to influence properties like gain mechanisms, lasing, quantum efficiency and transport even at room temperature due to the high and tunable trion binding energies.
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Affiliation(s)
- Sabrine Ayari
- Laboratoire de Physique des Materiaux, Faculte des Sciences de Bizerte, Universite de Carthage, Jarzouna 7021, Tunisia
| | - Michael T Quick
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
| | - Nina Owschimikow
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
| | | | | | - Mikhail Artemyev
- Research Institute for Physical Chemical Problems of Belarusian State University, 220006 Minsk, Belarus
| | - Iwan Moreels
- Department of Chemistry, Ghent University, Krijgslaan 281 - S3, 9000 Gent, Belgium
| | - Ulrike Woggon
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
| | - Sihem Jaziri
- Laboratoire de Physique des Materiaux, Faculte des Sciences de Bizerte, Universite de Carthage, Jarzouna 7021, Tunisia and Laboratoire de Physique de la Matiere Condensee, Departement de Physique, Faculte des Sciences de Tunis, Campus Universitaire, 1060 Tunis, Tunisia
| | - Alexander W Achtstein
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
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6
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Dufour M, Izquierdo E, Livache C, Martinez B, Silly MG, Pons T, Lhuillier E, Delerue C, Ithurria S. Doping as a Strategy to Tune Color of 2D Colloidal Nanoplatelets. ACS APPLIED MATERIALS & INTERFACES 2019; 11:10128-10134. [PMID: 30777752 DOI: 10.1021/acsami.8b18650] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Among colloidal nanocrystals, 2D nanoplatelets (NPLs) made of II-VI compounds appear as a special class of emitters with an especially narrow photoluminescence signal. However, the PL signal in the case of NPLs is only tunable by a discrete step. Here, we demonstrate that doping is a viable path to finely tune the color of these NPLs from green to red, making them extremely interesting as phosphors for wide-gamut display. In addition, using a combination of luminescence spectroscopy, tight-binding simulation, transport, and photoemission, we provide a consistent picture for the Ag+-doped CdSe NPLs. The Ag-activated state is strongly bound and located 340 meV above the valence band of the bulk material. The Ag dopant induces a relative shift of the Fermi level toward the valence band by up to 400 meV but preserves the n-type nature of the material.
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Affiliation(s)
- Marion Dufour
- Laboratoire de Physique et d'Etude des Matériaux , ESPCI-Paris, PSL Research University, Sorbonne Université UPMC Univ Paris 06, CNRS , 10 rue Vauquelin , 75005 Paris , France
| | - Eva Izquierdo
- Laboratoire de Physique et d'Etude des Matériaux , ESPCI-Paris, PSL Research University, Sorbonne Université UPMC Univ Paris 06, CNRS , 10 rue Vauquelin , 75005 Paris , France
| | - Clément Livache
- Laboratoire de Physique et d'Etude des Matériaux , ESPCI-Paris, PSL Research University, Sorbonne Université UPMC Univ Paris 06, CNRS , 10 rue Vauquelin , 75005 Paris , France
- Sorbonne Université, CNRS, Institut des nanosciences de Paris, INSP , F-75005 Paris , France
| | - Bertille Martinez
- Laboratoire de Physique et d'Etude des Matériaux , ESPCI-Paris, PSL Research University, Sorbonne Université UPMC Univ Paris 06, CNRS , 10 rue Vauquelin , 75005 Paris , France
- Sorbonne Université, CNRS, Institut des nanosciences de Paris, INSP , F-75005 Paris , France
| | - Mathieu G Silly
- Synchrotron-SOLEIL , Saint-Aubin, BP48, F91192 Gif-sur-Yvette , France
| | - Thomas Pons
- Laboratoire de Physique et d'Etude des Matériaux , ESPCI-Paris, PSL Research University, Sorbonne Université UPMC Univ Paris 06, CNRS , 10 rue Vauquelin , 75005 Paris , France
| | - Emmanuel Lhuillier
- Sorbonne Université, CNRS, Institut des nanosciences de Paris, INSP , F-75005 Paris , France
| | - Christophe Delerue
- Université de Lille, CNRS, Centrale Lille, ISEN, Université de Valenciennes, UMR 8520-IEMN , 59000 Lille , France
| | - Sandrine Ithurria
- Laboratoire de Physique et d'Etude des Matériaux , ESPCI-Paris, PSL Research University, Sorbonne Université UPMC Univ Paris 06, CNRS , 10 rue Vauquelin , 75005 Paris , France
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7
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Wieliczka BM, Kaledin AL, Buhro WE, Loomis RA. Wave Function Engineering in CdSe/PbS Core/Shell Quantum Dots. ACS NANO 2018; 12:5539-5550. [PMID: 29787230 DOI: 10.1021/acsnano.8b01248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The synthesis of epitaxial CdSe/PbS core/shell quantum dots (QDs) is reported. The PbS shell grows in a rock salt structure on the zinc blende CdSe core, thereby creating a crystal structure mismatch through additive growth. Absorption and photoluminescence (PL) band edge features shift to lower energies with increasing shell thickness, but remain above the CdSe bulk band gap. Nevertheless, the profiles of the absorption spectra vary with shell growth, indicating that the overlap of the electron and hole wave functions is changing significantly. This leads to over an order of magnitude reduction of absorption near the band gap and a large, tunable energy shift, of up to 550 meV, between the onset of strong absorption and the band edge PL. While the bulk valence and conduction bands adopt an inverse type-I alignment, the observed spectroscopic behavior is consistent with a transition between quasi-type-I and quasi-type-II behavior depending on shell thickness. Three effective mass approximation models support this hypothesis and suggest that the large difference in effective masses between the core and shell results in hole localization in the CdSe core and a delocalization of the electron across the entire QD. These results show the tuning of wave functions and transition energies in CdSe/PbS nanoheterostructures with prospects for use in optoelectronic devices for luminescent solar concentration or multiexciton generation.
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Affiliation(s)
- Brian M Wieliczka
- Department of Chemistry and Institute of Materials Science and Engineering , Washington University in St. Louis , One Brookings Drive, CB 1134 , Saint Louis , Missouri 63130 , United States
| | - Alexey L Kaledin
- Department of Chemistry and Cherry L. Emerson Center for Scientific Computation , Emory University , Atlanta , Georgia 30322 , United States
| | - William E Buhro
- Department of Chemistry and Institute of Materials Science and Engineering , Washington University in St. Louis , One Brookings Drive, CB 1134 , Saint Louis , Missouri 63130 , United States
| | - Richard A Loomis
- Department of Chemistry and Institute of Materials Science and Engineering , Washington University in St. Louis , One Brookings Drive, CB 1134 , Saint Louis , Missouri 63130 , United States
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8
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Hung SF, Chen ZZ, Chang CC, Hsu CS, Tsai MK, Kang CC, Chen HM. Dual-Hole Excitons Activated Photoelectrolysis in Neutral Solution. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1704047. [PMID: 29457346 DOI: 10.1002/smll.201704047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Revised: 12/21/2017] [Indexed: 06/08/2023]
Abstract
II-VI semiconductors exhibit unique behaviors that can generate dual-holes ("heavy and light"), but the application in photocatalysis is still missing. Herein, an empirical utilization of light/heavy holes in a hybrid metal cluster-2D semiconductor nanoplatelets is reported. This hybrid material can boost the hole-transfer at the surface and suppress the recombination. Different roles are enacted by light-holes and heavy-holes, in which the light-holes with higher energy and mobility can facilitate the slow kinetics of water oxidation and further reduce the onset voltage, while the massive heavy-holes can increase the resulting photocurrent by about five times, achieving a photocurrent of 2 mA cm-2 at 1.23 V versus RHE under AM 1.5 G illumination in nonsacrificial neutral solution. These strategies can be the solutions for photoelectrolysis and be beneficial for sustainable development in solar conversion.
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Affiliation(s)
- Sung-Fu Hung
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan
| | - Zhi-Zhong Chen
- Department of Chemistry, Fu Jen Catholic University, New Taipei City, 242, Taiwan
| | - Chun-Chih Chang
- Department of Chemistry, National Taiwan Normal University, Taipei, 116, Taiwan
| | - Chia-Shuo Hsu
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan
| | - Ming-Kang Tsai
- Department of Chemistry, National Taiwan Normal University, Taipei, 116, Taiwan
| | - Chia-Cheng Kang
- Department of Chemistry, Fu Jen Catholic University, New Taipei City, 242, Taiwan
| | - Hao Ming Chen
- Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan
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9
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Achtstein AW, Scott R, Kickhöfel S, Jagsch ST, Christodoulou S, Bertrand GHV, Prudnikau AV, Antanovich A, Artemyev M, Moreels I, Schliwa A, Woggon U. p-State Luminescence in CdSe Nanoplatelets: Role of Lateral Confinement and a Longitudinal Optical Phonon Bottleneck. PHYSICAL REVIEW LETTERS 2016; 116:116802. [PMID: 27035317 DOI: 10.1103/physrevlett.116.116802] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Indexed: 05/26/2023]
Abstract
We evidence excited state emission from p states well below ground state saturation in CdSe nanoplatelets. Size-dependent exciton ground and excited state energies and population dynamics are determined by four independent methods: time-resolved PL, time-integrated PL, rate equation modeling, and Hartree renormalized k·p calculations-all in very good agreement. The ground state-excited state energy spacing strongly increases with the lateral platelet quantization. Depending on its detuning to the LO phonon energy, the PL decay of CdSe platelets is governed by a size tunable LO phonon bottleneck, related to the low exciton-phonon coupling, very large oscillator strength, and energy spacing of both states. This is, for instance, ideal to tune lasing properties. CdSe platelets are perfectly suited to control the exciton-phonon interaction by changing their lateral size while the optical transition energy is determined by their thickness.
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Affiliation(s)
- Alexander W Achtstein
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Riccardo Scott
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Sebastian Kickhöfel
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Stefan T Jagsch
- Institute of Solid State Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Sotirios Christodoulou
- Department of Physics, University of Genoa, via Dodecaneso 33, IT-16146 Genova, Italy
- Istituto Italiano di Tecnologia, Via Morego 30, IT-16163 Genova, Italy
| | | | - Anatol V Prudnikau
- Institute for Physico-Chemical Problems, Belarusian State University, 220030 Minsk, Belarus
| | - Artsiom Antanovich
- Institute for Physico-Chemical Problems, Belarusian State University, 220030 Minsk, Belarus
| | - Mikhail Artemyev
- Institute for Physico-Chemical Problems, Belarusian State University, 220030 Minsk, Belarus
| | - Iwan Moreels
- Istituto Italiano di Tecnologia, Via Morego 30, IT-16163 Genova, Italy
| | - Andrei Schliwa
- Institute of Solid State Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Ulrike Woggon
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
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10
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Pedetti S, Ithurria S, Heuclin H, Patriarche G, Dubertret B. Type-II CdSe/CdTe Core/Crown Semiconductor Nanoplatelets. J Am Chem Soc 2014; 136:16430-8. [DOI: 10.1021/ja509307m] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Silvia Pedetti
- Nexdot, 10 rue Vauquelin, 75005 Paris, France
- Laboratoire de
Physique et d’Etude des Matériaux, ESPCI-ParisTech,
PSL Research University, Sorbonne Université UPMC Univ Paris
06, CNRS, 10 rue Vauquelin, 75005 Paris, France
| | - Sandrine Ithurria
- Laboratoire de
Physique et d’Etude des Matériaux, ESPCI-ParisTech,
PSL Research University, Sorbonne Université UPMC Univ Paris
06, CNRS, 10 rue Vauquelin, 75005 Paris, France
| | | | - Gilles Patriarche
- Laboratoire
Photonique
et Nanostructures, CNRS, 91460 Marcoussis, France
| | - Benoit Dubertret
- Laboratoire de
Physique et d’Etude des Matériaux, ESPCI-ParisTech,
PSL Research University, Sorbonne Université UPMC Univ Paris
06, CNRS, 10 rue Vauquelin, 75005 Paris, France
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11
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Moreels I, Rainò G, Gomes R, Hens Z, Stöferle T, Mahrt RF. Band-edge exciton fine structure of small, nearly spherical colloidal CdSe/ZnS quantum dots. ACS NANO 2011; 5:8033-8039. [PMID: 21961786 DOI: 10.1021/nn202604z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The exciton fine structure of small (2-3.5 nm) wurtzite (WZ) and zincblende (ZB) CdSe quantum dots (Qdots) has been investigated by means of nanosecond and picosecond time-resolved photoluminescence spectroscopy, at temperatures ranging from 5 K to room temperature. For both crystal structures, we observe a similar dark-bright energy level splitting of 2.4-5 meV, with a larger splitting corresponding to smaller Qdots. In addition, spectrally resolved streak camera images collected at 5 K reveal the presence of a third state, split from the lower dark-bright manifold by 30-70 meV, again independently of the crystal structure of the Qdots. The data thus reveal that small WZ and ZB CdSe Qdots are optically indistinguishable. This contrasts with theoretical calculations within the effective-mass approximation, which, in the limit of spherical Qdots, yield a different fine structure for both. However, experimental and theoretical results converge when taking the Qdot shape into account. With transmission electron microscopy, we determined that our Qdots are prolate, with an aspect ratio of 1.15:1. Incorporating this value into our calculations, we obtain a similar fine structure for both WZ and ZB Qdots. Moreover, the opposite sign of the crystal field and shape anisotropy in CdSe suggests that the lowest energy level in small CdSe Qdots has an angular momentum projection F = 0, in contrast with (perfectly) spherical Qdots, where the lowest level corresponds to the dark ±2 state. From the experimental and theoretical data we conclude that shape anisotropy and exchange interactions dominate over the crystal field anisotropy-induced splitting in this size range.
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Affiliation(s)
- Iwan Moreels
- IBM Research-Zürich, Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland.
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12
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Mahler B, Lequeux N, Dubertret B. Ligand-controlled polytypism of thick-shell CdSe/CdS nanocrystals. J Am Chem Soc 2010; 132:953-9. [PMID: 20043669 DOI: 10.1021/ja9034973] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the synthesis of CdSe/CdS semiconductor core/shell nanocrystals with very thick (5 nm) CdS shells. As in the case of core CdSe nanocrystals, we show that a thick-shell CdSe/CdS core/shell structure can be synthesized in either a pure wurtzite (W) or a zinc-blende (ZB) crystal structure. While the growth of thick-shell wurtzite CdSe/CdS is quite straightforward, we observe that the growth of a CdS shell on zinc-blende CdSe cores is more difficult and leads to wurtzite/zinc-blende polytypism when primary amines are present during the shell formation. Using absorption spectra analysis to differentiate zinc blende from wurtzite CdSe, we show that primary amines can induce a nearly complete structural transformation of CdSe ZB cores into W cores. This better understanding of the CdSe ligand-dependent crystal structural evolution during shell growth is further used to grow large (10 nm)-diameter perfect zinc-blende CdSe core crystals emitting above 700 nm, and perfect ZB thick-shell CdSe/CdS nanocrystals. We observed that all thick-shell CdSe/CdS QDs have extremely reduced blinking events compared to thin-shell QDs, without any significant influence of crystalline structure and polytypism.
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Affiliation(s)
- Benoît Mahler
- Laboratoire de Physique et d'Etude des Matériaux, CNRS UPR5, ESPCI 10 rue Vauquelin, 75231 Paris, France
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13
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Yoon YJ, Park KS, Heo JH, Park JG, Nahm S, Choi KJ. Synthesis of ZnxCd1−xSe (0 ≤x≤ 1) alloyed nanowires for variable-wavelength photodetectors. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/b917531h] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Ithurria S, Dubertret B. Quasi 2D Colloidal CdSe Platelets with Thicknesses Controlled at the Atomic Level. J Am Chem Soc 2008; 130:16504-5. [DOI: 10.1021/ja807724e] [Citation(s) in RCA: 578] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sandrine Ithurria
- Laboratoire Photons Et Matière, UPR5 du CNRS, ESPCI, 10 rue Vauquelin 75231 Paris, France
| | - Benoit Dubertret
- Laboratoire Photons Et Matière, UPR5 du CNRS, ESPCI, 10 rue Vauquelin 75231 Paris, France
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Firszt F, Wronkowska AA, Wronkowski A, ??gowski S, Marasek A, M?czy?ska H, Pawlak M, Paszkowicz W, Strza?kowski K, Zakrzewski AJ. Growth and optical characterization of Cd1-xBexSe and Cd1-xMgxSe crystals. CRYSTAL RESEARCH AND TECHNOLOGY 2005. [DOI: 10.1002/crat.200410355] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Lee J, Flack F, Samarth N, Collins RW. Composition and temperature dependence of the optical properties of Zn(1-x) Cd(x)Se (0 < or = x < or = 0.34) below the fundamental bandgap. APPLIED OPTICS 1997; 36:5372-5382. [PMID: 18259357 DOI: 10.1364/ao.36.005372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The II-VI ternary semiconductor alloy system Zn(1-x) Cd(x) Se with 0 < or = x < or = 0.2 has important applications as the active material in blue-green light-emitting diodes and lasers. For the wavelength and temperature ranges over which these devices are designed to operate, a knowledge of the optical properties of the alloys is important. We report the results of spectroscopic ellipsometry measurements of the real part of the dielectric function epsilon1 for Zn-rich Zn(1-x) Cd(x) Se layers deposited epitaxially on (100) GaAs. We derive compact expressions that allow one to calculate accurate epsilon1 spectra from 1.5 eV, the low-energy limit of our ellipsometer, to E0-0.05 eV, where E0 is the fundamental bandgap energy, for any composition and temperature within the ranges 0 < or = x < or = 0.34 and 25 < or = T < 260 degrees C. Furthermore, we expect that the results can also be extrapolated to cover the substrate temperature range typically used for the growth of these films (250-300 degrees C). Hence the results presented here are also useful in future real-time spectroscopic ellipsometry studies of Zn(1-x) Cd(x) Se film growth.
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Affiliation(s)
- J Lee
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Kim YD, Cooper SL, Klein MV, Park J, Jonker BT. Spectroscopic ellipsometry study of Zn1-xCoxSe alloys grown on GaAs. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:10637-10643. [PMID: 9975160 DOI: 10.1103/physrevb.50.10637] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Shan W, Song JJ, Luo H, Furdyna JK. Determination of the fundamental and split-off band gaps in zinc-blende CdSe by photomodulation spectroscopy. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:8012-8015. [PMID: 9974798 DOI: 10.1103/physrevb.50.8012] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Wen G, Chang YC. Theory of absorption spectra for above-barrier excitons in semiconductor superlattices. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 49:16585-16592. [PMID: 10010815 DOI: 10.1103/physrevb.49.16585] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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