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Slynchuk V, Schedel C, Scheele M, Schnepf A. Stabilization of Colloidal Germanium Nanoparticles: From the Study to the Prospects of the Application in Thin-Film Technology. Int J Mol Sci 2023; 24:15948. [PMID: 37958931 PMCID: PMC10649905 DOI: 10.3390/ijms242115948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/24/2023] [Accepted: 10/28/2023] [Indexed: 11/15/2023] Open
Abstract
We present the stabilization of halide-terminated Ge nanoparticles prepared via a disproportionation reaction of metastable Ge(I)X solutions with well-defined size distribution. Further tailoring of the stability of the Ge nanoparticles was achieved using variations in the substituent. Ge nanoparticles obtained in this way are readily dispersed in organic solvents, long-term colloidally stable, and are perfect prerequisites for thin-film preparation. This gives these nanomaterials a future in surface-dependent optical applications, as shown for the halide-terminated nanoparticles.
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Affiliation(s)
- Viktoriia Slynchuk
- Institute of Inorganic Chemistry, University of Tuebingen, Auf der Morgenstelle 18, D-72076 Tuebingen, Germany;
| | - Christine Schedel
- Institute of Physical and Theoretical Chemistry, University of Tuebingen, Auf der Morgenstelle 18, D-72076 Tuebingen, Germany (M.S.)
| | - Marcus Scheele
- Institute of Physical and Theoretical Chemistry, University of Tuebingen, Auf der Morgenstelle 18, D-72076 Tuebingen, Germany (M.S.)
| | - Andreas Schnepf
- Institute of Inorganic Chemistry, University of Tuebingen, Auf der Morgenstelle 18, D-72076 Tuebingen, Germany;
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Strauß F, Schedel C, Scheele M. Edge contacts accelerate the response of MoS 2 photodetectors. Nanoscale Adv 2023; 5:3494-3499. [PMID: 37383070 PMCID: PMC10295078 DOI: 10.1039/d3na00223c] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 06/02/2023] [Indexed: 06/30/2023]
Abstract
We use a facile plasma etching process to define contacts with an embedded edge geometry for multilayer MoS2 photodetectors. Compared to the conventional top contact geometry, the detector response time is accelerated by more than an order of magnitude by this action. We attribute this improvement to the higher in-plane mobility and direct contacting of the individual MoS2 layers in the edge geometry. With this method, we demonstrate electrical 3 dB bandwidths of up to 18 MHz which is one of the highest values reported for pure MoS2 photodetectors. We anticipate that this approach should also be applicable to other layered materials, guiding a way to faster next-generation photodetectors.
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Affiliation(s)
- Fabian Strauß
- Institute of Physical and Theoretical Chemistry, University of Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany
- LISA+, University of Tübingen Auf der Morgenstelle 15 72076 Tübingen Germany
| | - Christine Schedel
- Institute of Physical and Theoretical Chemistry, University of Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany
| | - Marcus Scheele
- Institute of Physical and Theoretical Chemistry, University of Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany
- LISA+, University of Tübingen Auf der Morgenstelle 15 72076 Tübingen Germany
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3
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Schedel C, Strauß F, Kohlschreiber P, Geladari O, Meixner AJ, Scheele M. Substrate effects on the speed limiting factor of WSe 2 photodetectors. Phys Chem Chem Phys 2022; 24:25383-25390. [PMID: 36239305 DOI: 10.1039/d2cp03364j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
We investigate the time-resolved photoelectric response of WSe2 crystals on glass and flexible polyimide substrates to determine the effect of a changed dielectric environment on the speed of the photodetectors. We show that varying the substrate material can alter the speed-limiting mechanism: while the detectors on polyimide are RC limited, those on glass are limited by slower excitonic diffusion processes. We attribute this to a shortening of the depletion layer at the metal electrode/WSe2 interface caused by the higher dielectric screening of glass compared to polyimide. The photodetectors on glass show a tunable bandwidth, which can be increased to 2.6 MHz with increasing the electric field.
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Affiliation(s)
- Christine Schedel
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Fabian Strauß
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, University of Tübingen, 72076 Tübingen, Germany.
| | - Pia Kohlschreiber
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Olympia Geladari
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Alfred J Meixner
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, University of Tübingen, 72076 Tübingen, Germany.
| | - Marcus Scheele
- Institute for Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, University of Tübingen, 72076 Tübingen, Germany.
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Maier A, Strauß F, Kohlschreiber P, Schedel C, Braun K, Scheele M. Sub-nanosecond Intrinsic Response Time of PbS Nanocrystal IR-Photodetectors. Nano Lett 2022; 22:2809-2816. [PMID: 35311295 DOI: 10.1021/acs.nanolett.1c04938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Colloidal nanocrystals (NCs), especially lead sulfide NCs, are promising candidates for solution-processed next-generation photodetectors with high-speed operation frequencies. However, the intrinsic response time of PbS-NC photodetectors, which is the material-specific physical limit, is still elusive, as the reported response times are typically limited by the device geometry. Here, we use the two-pulse coincidence photoresponse technique to identify the intrinsic response time of 1,2-ethanedithiol-functionalized PbS-NC photodetectors after femtosecond-pulsed 1560 nm excitation. We obtain an intrinsic response time of ∼1 ns, indicating an intrinsic bandwidth of ∼0.55 GHz as the material-specific limit. Examination of the dependence on laser power, gating, bias, temperature, channel length, and environmental conditions suggest that Auger recombination, assisted by NC-surface defects, is the dominant mechanism. Accordingly, the intrinsic response time might further be tuned by specifically controlling the ligand coverage and trap states. Thus, PbS-NC photodetectors are feasible for gigahertz optical communication in the third telecommunication window.
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Affiliation(s)
- Andre Maier
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, Universität Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
| | - Fabian Strauß
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, Universität Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
| | - Pia Kohlschreiber
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, Universität Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
| | - Christine Schedel
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076Tübingen, Germany
| | - Kai Braun
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, Universität Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
| | - Marcus Scheele
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, D-72076Tübingen, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, Universität Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
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Schedel C, Strauß F, Kumar K, Maier A, Wurst KM, Michel P, Scheele M. Substrate Effects on the Bandwidth of CdSe Quantum Dot Photodetectors. ACS Appl Mater Interfaces 2021; 13:47954-47961. [PMID: 34605623 DOI: 10.1021/acsami.1c13581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We investigate the time-resolved photocurrent response of CdSe quantum dot (QD) thin films sensitized with zinc β-tetraaminophthalocyanine (Zn4APc) (Kumar , ACS Appl. Mater. Interfaces, 2019, 11, 48271-48280) on three different substrates, namely, silicon with 230 nm SiO2 dielectric, glass, and polyimide. While Si/SiO2 (230 nm) is not suitable for any transient photocurrent characterization due to an interfering photocurrent response of the buried silicon, we find that polyimide substrates invoke the larger optical bandwidth with 85 kHz vs 67 kHz for the same quantum dot thin film on glass. Upon evaluation of the transient photocurrent, we find that the photoresponse of the CdSe quantum dot films can be described as a combination of carrier recombination and fast trapping within 2.7 ns followed by slower multiple trapping events. The latter are less pronounced on polyimide, which leads to the higher bandwidth. We show that all devices are resistance-capacitance (RC)-time limited and that improvements of photoresistance are the key to further increasing the bandwidth.
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Affiliation(s)
- Christine Schedel
- Institute for Physical and Theoretical Chemistry, University of Tübingen, Tübingen 72076, Germany
| | - Fabian Strauß
- Institute for Physical and Theoretical Chemistry, University of Tübingen, Tübingen 72076, Germany
| | - Krishan Kumar
- Institute for Physical and Theoretical Chemistry, University of Tübingen, Tübingen 72076, Germany
| | - Andre Maier
- Institute for Physical and Theoretical Chemistry, University of Tübingen, Tübingen 72076, Germany
| | - Kai M Wurst
- Institute for Physical and Theoretical Chemistry, University of Tübingen, Tübingen 72076, Germany
| | - Patrick Michel
- Institute for Physical and Theoretical Chemistry, University of Tübingen, Tübingen 72076, Germany
| | - Marcus Scheele
- Institute for Physical and Theoretical Chemistry, University of Tübingen, Tübingen 72076, Germany
- Center for Light-Matter Interaction, Sensors and Analytics LISA+, University of Tübingen, Tübingen 72076, Germany
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Kumar K, Liu Q, Hiller J, Schedel C, Maier A, Meixner A, Braun K, Lauth J, Scheele M. Fast, Infrared-Active Optical Transistors Based on Dye-Sensitized CdSe Nanocrystals. ACS Appl Mater Interfaces 2019; 11:48271-48280. [PMID: 31778068 DOI: 10.1021/acsami.9b18236] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report an optically gated transistor composed of CdSe nanocrystals (NCs), sensitized with the dye zinc β-tetraaminophthalocyanine for operation in the first telecom window. This device shows a high ON/OFF ratio of 6 orders of magnitude in the red spectral region and an unprecedented 4.5 orders of magnitude at 847 nm. By transient absorption spectroscopy, we reveal that this unexpected infrared sensitivity is due to electron transfer from the dye to the CdSe NCs within 5 ps. We show by time-resolved photocurrent measurements that this enables fast rise times during near-infrared optical gating of 47 ± 11 ns. Electronic coupling and accelerated nonradiative recombination of charge carriers at the interface between the dye and the CdSe NCs are further corroborated by steady-state and time-resolved photoluminescence measurements. Field-effect transistor measurements indicate that the increase in photocurrent upon laser illumination is mainly due to the increase in the carrier concentration while the mobility remains unchanged. Our results illustrate that organic dyes as ligands for NCs invoke new optoelectronic functionalities, such as fast optical gating at sub-bandgap optical excitation energies.
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Affiliation(s)
- Krishan Kumar
- Institute for Physical and Theoretical Chemistry , University of Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
| | - Quan Liu
- Institute for Physical and Theoretical Chemistry , University of Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
- Charles Delaunay Institute , CNRS Light, Nanomaterials, Nanotechnologies (L2n, former "LNIO") University of Technology of Troyes , 12 rue Marie Curie-CS 42060 , 10004 Troyes Cedex, France
| | - Jonas Hiller
- Institute for Physical and Theoretical Chemistry , University of Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
| | - Christine Schedel
- Institute for Physical and Theoretical Chemistry , University of Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
| | - Andre Maier
- Institute for Physical and Theoretical Chemistry , University of Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
| | - Alfred Meixner
- Institute for Physical and Theoretical Chemistry , University of Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
- Center for Light-Matter Interaction, Sensors & Analytics LISA+ , University of Tübingen , Auf der Morgenstelle 15 , 72076 Tübingen , Germany
| | - Kai Braun
- Institute for Physical and Theoretical Chemistry , University of Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
| | - Jannika Lauth
- Institute for Physical Chemistry and Electrochemistry , Universität Hannover , Callinstr. 3A , 30167 Hannover , Germany
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering-Innovation Across Disciplines) , D-30167 Hannover , Germany
| | - Marcus Scheele
- Institute for Physical and Theoretical Chemistry , University of Tübingen , Auf der Morgenstelle 18 , 72076 Tübingen , Germany
- Center for Light-Matter Interaction, Sensors & Analytics LISA+ , University of Tübingen , Auf der Morgenstelle 15 , 72076 Tübingen , Germany
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Balle D, Schedel C, Chassé T, Peisert H. Interface properties of CoPc and CoPcF 16 on graphene/nickel: influence of germanium intercalation. J Phys Condens Matter 2019; 31:174004. [PMID: 30695754 DOI: 10.1088/1361-648x/ab028f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Photoelectron spectroscopy was used to investigate electronic interface properties and interactions of the organic semiconductors CoPc and CoPcF16 on graphene/nickel based substrates. Additional focus was put on the influence of germanium intercalation of graphene/nickel. The presented results demonstrate that germanium can decouple graphene from nickel and in this manner restore its buffer layer properties. No charge transfer from the substrate to the organic layer is observed in the germanium intercalated case, while interface related peaks in the Co 2p core level spectra indicate such charge transfer on graphene/nickel. Strong interface dipoles are found for CoPcF16 on graphene/nickel and on germanium intercalated graphene/nickel. Fluorine Auger parameters have been measured, and the results provide evidence for polarization and charge transfer screening effects of different amounts at the unlike film-substrate interfaces. The various contributions to the observed shifts are discussed.
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Affiliation(s)
- David Balle
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
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Dolabdjian K, Schedel C, Enseling D, Jüstel T, Meyer HJ. Synthesis, Luminescence and Nonlinear Optical Properties of Homoleptic TetracyanamidogermanatesARE[Ge(CN2)4] (A= K, Cs, andRE= La, Ce, Pr, Nd, Sm, Eu, Gd). Z Anorg Allg Chem 2017. [DOI: 10.1002/zaac.201600353] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Konstantin Dolabdjian
- Abteilung für Festkörperchemie und Theoretische Anorganische Chemie; Institut für Anorganische Chemie; Universität Tübingen; Auf der Morgenstelle 18 72076 Tübingen Germany
| | - Christine Schedel
- Abteilung für Festkörperchemie und Theoretische Anorganische Chemie; Institut für Anorganische Chemie; Universität Tübingen; Auf der Morgenstelle 18 72076 Tübingen Germany
| | - David Enseling
- Fachbereich Chemieingenieurwesen; FH Münster; Stegerwaldstraße 39 48565 Steinfurt Germany
| | - Thomas Jüstel
- Fachbereich Chemieingenieurwesen; FH Münster; Stegerwaldstraße 39 48565 Steinfurt Germany
| | - Hans-Jürgen Meyer
- Abteilung für Festkörperchemie und Theoretische Anorganische Chemie; Institut für Anorganische Chemie; Universität Tübingen; Auf der Morgenstelle 18 72076 Tübingen Germany
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Abstract
Abstract
We use the photochromic organic semiconductor 1,2-Bis(5′-carboxy-2′-methylthien-3′-yl)-cyclopentene (DTCP) to cross-link PbS quantum dots assembled into thin films. The ligand exchange is monitored by means of vibrational spectroscopy (FT-IR) and core-level X-ray photoemission spectroscopy (XPS). Transport measurements in a field-effect transistor (FET) set-up reveal ambipolar behavior with hole and electron mobilities on the order of 10−4 cm2/Vs and 10−5 cm2/Vs, respectively. Exposure to UV light from a 4 W UV lamp does not significantly change the transport properties, indicating that switching of DTCP is hindered in the hybrid film. We find a pronounced photo-conductance with rapid and reversible photo-response on the order of few seconds, which we attribute to (de-)filling of QD trap states. Our results indicate that hybrid, nanostructured networks of PbS QDs cross-linked with DTCP can be obtained by the presented procedure but that switching of the QD-bound DTCP appears to be hindered compared to the pure, unbound molecular species. We discuss future means to address this problem.
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Affiliation(s)
- Christine Schedel
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Robert Thalwitzer
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Mahdi Samadi Khoshkhoo
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Marcus Scheele
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
- Center for Light-Matter Interaction, Sensors & Analytics LISA+, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
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Abstract
The authors studied how supralinearity influences individual "deep trap" terms (or levels) of a glow curve that represents the luminous flux emitted by heated LiF rods as a function of energy required for heating. It is assumed that a Gaussian function can be used for glow curve analysis, developing measured glow curves to represent individual "deep trap" terms. Analysis reveals that supralinearity occurs much earlier and more markedly with high temperature peaks than with low ones. This has a bearing on practice.
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