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Mildner A, Horrer A, Weiss P, Dickreuter S, Simo PC, Gérard D, Kern DP, Fleischer M. Decoding Polarization in a Single Achiral Gold Nanostructure from Emitted Far-Field Radiation. ACS Nano 2023; 17:25656-25666. [PMID: 38071648 DOI: 10.1021/acsnano.3c10398] [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: 12/27/2023]
Abstract
The emergence of optical chirality in the light emitted from plasmonic nanostructures is commonly associated with their geometrical chirality. Although it has been demonstrated that even achiral structures can exhibit chiral near-fields, the existence of chiroptical far-field responses of such structures is widely neglected. In this paper, we present a detailed analysis of the polarization state in a single planar achiral plasmonic nanostructure that sustains more than one prominent plasmon mode. In consideration of the relative phase, the superposition of the fields associated with these modes determines the polarization state of the emitted light in the far-field. Supported by simulations of the surface charge distribution of the particle, we show that the polarization state of the emitted light is already determined in the near-field. The chiroptical far-field responses are analyzed by polarized single-particle dark-field scattering spectroscopy. We introduce an analytical model that enables us to obtain the polarization information from the spectra of structures with dipolar resonances taken under unpolarized illumination. The same principle is confirmed in polarimetric spectroscopy measurements on rhomboids with systematically varied angles, therefore, introducing increasing values of geometrical chirality to the structures. The agreement between the calculation and measurement demonstrates the general validity of our model for both chiral and achiral structures.
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Affiliation(s)
- Annika Mildner
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics LISA+, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Andreas Horrer
- Light, nanomaterials, nanotechnologies (L2n), CNRS EMR 7004, Université de Technologie de Troyes, Troyes 10004, France
| | - Patrizia Weiss
- Department of Physics, University of Tübingen, Auf der Morgenstelle 14, 72076 Tübingen, Germany
| | - Simon Dickreuter
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - P Christian Simo
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics LISA+, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Davy Gérard
- Light, nanomaterials, nanotechnologies (L2n), CNRS EMR 7004, Université de Technologie de Troyes, Troyes 10004, France
| | - Dieter P Kern
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics LISA+, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Monika Fleischer
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics LISA+, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
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2
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Gürdal E, Horneber A, Meixner AJ, Kern DP, Zhang D, Fleischer M. Enhancement of the second harmonic signal of nonlinear crystals by a single metal nanoantenna. Nanoscale 2020; 12:23105-23115. [PMID: 33180087 DOI: 10.1039/d0nr05696k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This work fundamentally investigates how the second harmonic generation (SHG) from commercial nonlinear crystals can be boosted by the addition of individual optical nanoantennas. Frequency conversion plays an important role in modern non-linear optics, and nonlinear crystals have become a widely used building block for non-linear processes. Still, SHG remains hampered by limited conversion efficiency. To strengthen SHG from the crystal surface, we investigate the interaction of LiNbO3 crystals with individual gold nanodiscs. The scattered intensities and resonance frequencies of the nanodiscs are analyzed by dark-field spectroscopy and simulations. Subsequently, the discs on LiNbO3 are excited by a pulsed femtosecond laser in a parabolic mirror setup. Comparing the SHG at the position of a single nanodisc at resonance on the crystal with that of the unstructured crystal and of gold nanodiscs on a reference substrate, local SHG enhancement of up to a factor of three was achieved in the focal volume through the presence of the antenna.
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Affiliation(s)
- Emre Gürdal
- Institute for Applied Physics, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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3
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Schäfer C, Perera PN, Laible F, Olynick DL, Schwartzberg AM, Weber-Bargioni A, Cabrini S, Schuck PJ, Kern DP, Fleischer M. Selectively accessing the hotspots of optical nanoantennas by self-aligned dry laser ablation. Nanoscale 2020; 12:19170-19177. [PMID: 32926034 DOI: 10.1039/d0nr04024j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Plasmonic nanostructures serve as optical antennas for concentrating the energy of incoming light in localized hotspots close to their surface. By positioning nanoemitters in the antenna hotspots, energy transfer is enabled, leading to novel hybrid antenna-emitter-systems, where the antenna can be used to manipulate the optical properties of the nano-objects. The challenge remains how to precisely position emitters within the hotspots. We report a self-aligned process based on dry laser ablation of a calixarene that enables the attachment of molecules within the electromagnetic hotspots at the tips of gold nanocones. Within the laser focus, the ablation threshold is exceeded in nanoscale volumes, leading to selective access of the hotspot areas. A first indication of the site-selective functionalization process is given by attaching fluorescently labelled proteins to the nanocones. In a second example, Raman-active molecules are selectively attached only to nanocones that were previously exposed in the laser focus, which is verified by surface enhanced Raman spectroscopy. Enabling selective functionalization is an important prerequisite e.g. for preparing single photon sources for quantum optical technologies, or multiplexed Raman sensing platforms.
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Affiliation(s)
- Christian Schäfer
- Institute for Applied Physics and Center LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
| | - Pradeep N Perera
- The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Building 67, Berkeley, CA 94720, USA
| | - Florian Laible
- Institute for Applied Physics and Center LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
| | - Deirdre L Olynick
- The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Building 67, Berkeley, CA 94720, USA
| | - Adam M Schwartzberg
- The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Building 67, Berkeley, CA 94720, USA
| | - Alexander Weber-Bargioni
- The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Building 67, Berkeley, CA 94720, USA
| | - Stefano Cabrini
- The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Building 67, Berkeley, CA 94720, USA
| | - P James Schuck
- The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Building 67, Berkeley, CA 94720, USA
| | - Dieter P Kern
- Institute for Applied Physics and Center LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
| | - Monika Fleischer
- Institute for Applied Physics and Center LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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4
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Gürdal E, Horneber A, Shaqqura N, Meixner AJ, Kern DP, Zhang D, Fleischer M. Enhancement of the second harmonic signal of nonlinear crystals by self-assembled gold nanoparticles. J Chem Phys 2020; 152:104711. [PMID: 32171201 DOI: 10.1063/1.5139893] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In second harmonic generation (SHG), the energy of two incoming photons, e.g., from a femtosecond laser, can be combined in one outgoing photon of twice the energy, e.g., by means of a nonlinear crystal. The SHG efficiency, however, is limited. In this work, the harvested signal is maximized by composing a hybrid system consisting of a nonlinear crystal with a dense coverage of plasmonic nanostructures separated by narrow gaps. The method of self-assembled diblock-copolymer-based micellar lithography with subsequent electroless deposition is employed to cover the whole surface of a lithium niobate (LiNbO3) crystal. The interaction of plasmonic nanostructures with light leads to a strong electric near-field in the adjacent crystal. This near-field is harnessed to enhance the near-surface SHG signal from the nonlinear crystal. At the plasmon resonance of the gold nanoparticles, a pronounced enhancement of about 60-fold SHG is observed compared to the bare crystal within the confocal volume of a laser spot.
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Affiliation(s)
- Emre Gürdal
- Institute for Applied Physics and Center LISA, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Anke Horneber
- Institute of Physical and Theoretical Chemistry and Center LISA, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Nadim Shaqqura
- Institute for Applied Physics and Center LISA, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Alfred J Meixner
- Institute of Physical and Theoretical Chemistry and Center LISA, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Dieter P Kern
- Institute for Applied Physics and Center LISA, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Dai Zhang
- Institute of Physical and Theoretical Chemistry and Center LISA, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Monika Fleischer
- Institute for Applied Physics and Center LISA, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
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5
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Seitl L, Laible F, Dickreuter S, Gollmer DA, Kern DP, Fleischer M. Miniaturized fractal optical nanoantennas defined by focused helium ion beam milling. Nanotechnology 2020; 31:075301. [PMID: 31725410 DOI: 10.1088/1361-6528/ab5120] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
It has been shown in the past that fractal geometries are beneficial for radio and communication antenna designs in terms of bandwidth and gain. Recently, this concept was extended to plasmonic nanoantennas. Here, we present a fabrication method based on electron beam lithography and focused helium ion beam milling to further miniaturize dimer nanoantennas of 0th, 1st and 2nd order Sierpiński fractals. With this state-of-the-art approach, it becomes feasible to experimentally move their resonance conditions into the sub-micron wavelength regime, while maintaining excellent pattern definition and achieving sub-10 nm gap sizes for high near-field enhancement. These highly sophisticated nanostructures are numerically simulated and analyzed by dark-field scattering spectroscopy to monitor the effects of the fractal structuring on the scattering spectra and near-field enhancement.
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Affiliation(s)
- Lisa Seitl
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen, Germany. Center for Light-Matter-Interaction, Sensors and Analytics LISA+, University of Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
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6
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Dreser C, Gürdal E, Bautista G, Horneber A, Zang X, Gollmer DA, Meixner AJ, Kern DP, Zhang D, Kauranen M, Fleischer M. Second harmonic generation enhancement by polarization-matched nanostructures -INVITED. EPJ Web Conf 2020. [DOI: 10.1051/epjconf/202023805001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Frequency conversion plays an important role in both fundamental and applied nano-optics. Doubling the frequency of light by second harmonic generation (SHG) is a vital process e.g. in laser optics or high-resolution microscopy. SHG can be created through symmetry breaking at plasmonic nanostructures, or the local high electric near-fields of plasmonic nanoantennas can be utilized to further enhance the SHG e.g. from nonlinear crystals. Examples of SHG microscopy using cylindrical vector beams in combination with tilted nanocones and radially symmetric oligomers are shown as well as enhancement studies of the SHG from nonlinear crystals decorated with polarization-matched nanostructures.
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7
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Fulmes J, Schäfer C, Kern DP, Adam PM, Fleischer M. Relative spectral tuning of the vertical versus base modes in plasmonic nanocones. Nanotechnology 2019; 30:415201. [PMID: 31339108 DOI: 10.1088/1361-6528/ab2d5c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Gold nanocones acting as optical antennas offer an excellent geometry for focusing light near the cone tip, acting as nano-light sources with spot sizes on the order of the tip radius. However only the vertical plasmon mode oscillating in the axial direction can effectively excite the tip, whereas lateral modes oscillating along the cone base create mostly unwanted background in applications. The present work investigates the three-dimensional plasmonic mode structure of nanocones both experimentally and numerically. By tuning the nanocone aspect ratio, the modes can be spectrally tuned relative to each other, making them coincide for maximum excitation, or tuning the base mode away from the vertical mode for effective background suppression.
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Affiliation(s)
- Julia Fulmes
- Institute for Applied Physics and Center LISA+, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10 and 15, 72076 Tübingen, Germany
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8
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Laible F, Dreser C, Kern DP, Fleischer M. Time-effective strategies for the fabrication of poly- and single-crystalline gold nano-structures by focused helium ion beam milling. Nanotechnology 2019; 30:235302. [PMID: 30907377 DOI: 10.1088/1361-6528/ab0506] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [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
Milling with the focused helium ion beam of a helium ion microscope is one of the most accurate ways to produce nano-structures such as plasmonic nanoantennas. In addition to good and immediate control of the dimensions, features in the sub-10 nm regime are achievable. Especially small gaps and sharp tips in this regime may lead to very high field enhancement under excitation. However, the milling rate of 30 keV helium ions is rather low, making it time-consuming to cut nano-structures out of a gold film. We present two processes to work around the low milling rate to obtain arrays of nano-structures with maximum precision within a reasonable time. These strategies can both be adapted to either poly-crystalline gold films or single-crystalline gold flakes. Using single crystals from a fabrication point of view enables even higher precision due to constant etch rates over the whole crystal as well as straight edges and vertical side-walls due to the uniform crystalline structure.
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Affiliation(s)
- Florian Laible
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen, Germany. Center for Light-Matter-Interaction, Sensors and Analytics LISA+, University of Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
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9
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Dreser C, Gollmer DA, Bautista G, Zang X, Kern DP, Kauranen M, Fleischer M. Plasmonic mode conversion in individual tilted 3D nanostructures. Nanoscale 2019; 11:5429-5440. [PMID: 30855057 DOI: 10.1039/c8nr10254f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [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
We investigate mode conversion in 3D asymmetric nanocones using angle-dependent linear optical spectroscopy and second-harmonic generation microscopy supported by corresponding simulations. The results prove the efficient excitation of the plasmonic out-of-plane mode that enhances the electric near-field at the sharp tip. Furthermore, we introduce two advanced fabrication processes including either etch mask transfer by tilted etching into a metallic layer or tilted electron-beam lithography followed by tilted evaporation and lift-off. These processes enable the fabrication of tilted nanostructures which can be optimized for a given purpose. The combination of the optical properties and the introduced fabrication processes enables a new design of plasmonic nanostructures for ultra-compact sensors or photon sources.
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Affiliation(s)
- Christoph Dreser
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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10
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Laible F, Gollmer DA, Dickreuter S, Kern DP, Fleischer M. Continuous reversible tuning of the gap size and plasmonic coupling of bow tie nanoantennas on flexible substrates. Nanoscale 2018; 10:14915-14922. [PMID: 30044459 DOI: 10.1039/c8nr03575j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
As a multifunctional device for sensing experiments and fundamental research, tailor-made plasmonic nanostructures with continuously tunable resonances are created by preparing bow tie-shaped nanostructures on a flexible substrate. The bow ties are fabricated by electron beam lithography on a chromium sacrificial layer and transferred to a polydimethylsiloxane (PDMS) substrate. The structures on PDMS are analyzed by reflection dark-field spectroscopy and scanning electron microscopy. Dark-field spectra of individual nano-antennas are obtained while the substrate is relaxed, and while strain is applied and the substrate is elastically stretched. Depending on the alignment of the bow ties relative to the direction of the strain, the deformation of the substrates leads to an increase or decrease of the nanostructure gaps, and therefore to a fully reversible decrease or increase of the antenna coupling, respectively. The continuous change in coupling is visible as a blue-shift in the resonance of the coupling mode for increasing gap widths, and a red-shift for decreasing gap widths. This configuration offers interesting perspectives for molecular transport and sensing investigations under variable coupling conditions as well as for tunable SERS substrates and optical strain sensor applications. In particular, very narrow gaps are within reach in the transversal configuration.
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Affiliation(s)
- Florian Laible
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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11
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Gürdal E, Dickreuter S, Noureddine F, Bieschke P, Kern DP, Fleischer M. Self-assembled quasi-hexagonal arrays of gold nanoparticles with small gaps for surface-enhanced Raman spectroscopy. Beilstein J Nanotechnol 2018; 9:1977-1985. [PMID: 30116689 PMCID: PMC6071734 DOI: 10.3762/bjnano.9.188] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 06/20/2018] [Indexed: 05/26/2023]
Abstract
The fabrication and optical characterization of self-assembled arrangements of rough gold nanoparticles with a high area coverage and narrow gaps for surface-enhanced Raman spectroscopy (SERS) are reported. A combination of micellar nanolithography and electroless deposition (ED) enables the tuning of the spacing and size of the noble metal nanoparticles. Long-range ordered quasi-hexagonal arrays of gold nanoparticles on silicon substrates with a variation of the particle sizes from about 20 nm to 120 nm are demonstrated. By increasing the particle sizes for the homogeneously spaced particles, a large number of narrow gaps is created, which together with the rough surface of the particles induces a high density of intense hotspots. This makes the surfaces interesting for future applications in near-field-enhanced bio-analytics of molecules. SERS was demonstrated by measuring Raman spectra of 4-MBA on the gold nanoparticles. It was verified that a smaller inter-particle distance leads to an increased SERS signal.
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Affiliation(s)
- Emre Gürdal
- Institute for Applied Physics, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics (LISA+), Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Simon Dickreuter
- Institute for Applied Physics, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics (LISA+), Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Fatima Noureddine
- Institute for Applied Physics, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics (LISA+), Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Pascal Bieschke
- Institute for Applied Physics, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics (LISA+), Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Dieter P Kern
- Institute for Applied Physics, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics (LISA+), Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Monika Fleischer
- Institute for Applied Physics, Eberhard Karls University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics (LISA+), Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
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12
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Fulmes J, Gollmer DA, Jäger S, Schäfer C, Horrer A, Zhang D, Adam PM, Meixner AJ, Kern DP, Fleischer M. Mapping the electric field distribution of tightly focused cylindrical vector beams with gold nanorings. Opt Express 2018; 26:14982-14998. [PMID: 30114752 DOI: 10.1364/oe.26.014982] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 04/23/2018] [Indexed: 06/08/2023]
Abstract
In this paper gold nanorings (NRs) are applied as particularly well-suited sensing elements for mapping the radially symmetric electric fields in the high numerical aperture focus of cylindrical vector beams. The optical properties of gold nanorings are analyzed by a combination of extinction and single particle dark field spectroscopy as well as confocal photoluminescence (PL) imaging. The results are compared to numerical calculations. The in-plane components in the focus of the cylindrical vector beams are estimated through the PL intensity distributions of the NRs. The optimum overlap between the structure and excitation is visualized by a narrow centre spot in the far-field PL scan.
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13
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Bautista G, Dreser C, Zang X, Kern DP, Kauranen M, Fleischer M. Collective Effects in Second-Harmonic Generation from Plasmonic Oligomers. Nano Lett 2018; 18:2571-2580. [PMID: 29584937 PMCID: PMC6150722 DOI: 10.1021/acs.nanolett.8b00308] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 03/20/2018] [Indexed: 06/08/2023]
Abstract
We investigate collective effects in plasmonic oligomers of different symmetries using second-harmonic generation (SHG) microscopy with cylindrical vector beams (CVBs). The oligomers consist of gold nanorods that have a longitudinal plasmon resonance close to the fundamental wavelength that is used for SHG excitation and whose long axes are arranged locally such that they follow the distribution of the transverse component of the electric field of radially or azimuthally polarized CVBs in the focal plane. We observe that SHG from such rotationally symmetric oligomers is strongly modified by the interplay between the polarization properties of the CVB and interparticle coupling. We find that the oligomers with radially oriented nanorods exhibit small coupling effects. In contrast, we find that the oligomers with azimuthally oriented nanorods exhibit large coupling effects that lead to silencing of SHG from the whole structure. Our experimental results are in very good agreement with numerical calculations based on the boundary element method. The work describes a new route for studying coupling effects in complex arrangements of nano-objects and thereby for tailoring the efficiency of nonlinear optical effects in such structures.
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Affiliation(s)
- Godofredo Bautista
- Laboratory
of Photonics, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere, Finland
| | - Christoph Dreser
- Institute
for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center
for Light-Matter-Interaction, Sensors and Analytics LISA, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Xiaorun Zang
- Laboratory
of Photonics, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere, Finland
| | - Dieter P. Kern
- Institute
for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center
for Light-Matter-Interaction, Sensors and Analytics LISA, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
| | - Martti Kauranen
- Laboratory
of Photonics, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere, Finland
| | - Monika Fleischer
- Institute
for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
- Center
for Light-Matter-Interaction, Sensors and Analytics LISA, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany
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14
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Horrer A, Haas J, Freudenberger K, Gauglitz G, Kern DP, Fleischer M. Compact plasmonic optical biosensors based on nanostructured gradient index lenses integrated into microfluidic cells. Nanoscale 2017; 9:17378-17386. [PMID: 29095450 DOI: 10.1039/c7nr04097k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report on a compact and cost-effective integrated label-free biosensor configuration which is based on the refractive index sensitivity of the localized surface plasmon resonance (LSPR) of gold nanostructures. Aiming for compactification and miniaturization of the sensor, arrays of nanodiscs were fabricated on the planar surface of a gradient index (GRIN) lens, which acts as a substrate as well as an imaging objective for the light scattered by the gold structures. Integration of the lens into a microfluidic flow cell enabled the controlled exchange of liquid media at the sensor surface. The light scattered by the nanostructures was investigated spatially and spectrally resolved making use of the imaging properties of the GRIN lens. Dynamic spectral analysis during refractive index changes was conducted, revealing high sensitivities of up to 372 nm per refractive index unit for the shift of the LSPR. Biosensing capabilities were demonstrated by the detection of binding of an analyte by means of a testosterone-immunoassay.
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Affiliation(s)
- A Horrer
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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15
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Meixner AJ, Jäger R, Jäger S, Bräuer A, Scherzinger K, Fulmes J, Krockhaus SZO, Gollmer DA, Kern DP, Fleischer M. Coupling single quantum dots to plasmonic nanocones: optical properties. Faraday Discuss 2015; 184:321-37. [PMID: 26404008 DOI: 10.1039/c5fd00074b] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Coupling a single quantum emitter, such as a fluorescent molecule or a quantum dot (QD), to a plasmonic nanostructure is an important issue in nano-optics and nano-spectroscopy, relevant for a wide range of applications, including tip-enhanced near-field optical microscopy, plasmon enhanced molecular sensing and spectroscopy, and nanophotonic amplifiers or nanolasers, to mention only a few. While the field enhancement of a sharp nanoantenna increasing the excitation rate of a very closely positioned single molecule or QD has been well investigated, the detailed physical mechanisms involved in the emission of a photon from such a system are, by far, less investigated. In one of our ongoing research projects, we try to address these issues by constructing and spectroscopically analysing geometrically simple hybrid heterostructures consisting of sharp gold cones with single quantum dots attached to the very tip apex. An important goal of this work is to tune the longitudinal plasmon resonance by adjusting the cones' geometry to the emission maximum of the core-shell CdSe/ZnS QDs at nominally 650 nm. Luminescence spectra of the bare cones, pure QDs and hybrid systems were distinguished successfully. In the next steps we will further investigate, experimentally and theoretically, the optical properties of the coupled systems in more detail, such as the fluorescence spectra, blinking statistics, and the current results on the fluorescence lifetimes, and compare them with uncoupled QDs to obtain a clearer picture of the radiative and non-radiative processes.
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Affiliation(s)
- Alfred J Meixner
- Center for Light-Matter Interaction, Sensors & Analytics (LISA+), Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany.
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16
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Fulmes J, Jäger R, Bräuer A, Schäfer C, Jäger S, Gollmer DA, Horrer A, Nadler E, Chassé T, Zhang D, Meixner AJ, Kern DP, Fleischer M. Self-aligned placement and detection of quantum dots on the tips of individual conical plasmonic nanostructures. Nanoscale 2015; 7:14691-14696. [PMID: 26280199 DOI: 10.1039/c5nr03546e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Hybrid structures of few or single quantum dots (QDs) coupled to single optical antennas are of prime interest for nano-optical research. The photoluminescence (PL) signal from single nanoemitters, such as QDs, can be enhanced, and their emission characteristics modified, by coupling them to plasmonic nanostructures. Here, a self-aligned technique for placing nanoscale QDs with about 10 nm lateral accuracy and well-defined molecular distances to the tips of individual nanocones is reported. This way the QDs are positioned exactly in the high near-field region that can be created near the cone apex. The cones are excited in the focus of a radially polarized laser beam and the PL signal of few or single QDs on the cone tips is spectrally detected.
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Affiliation(s)
- Julia Fulmes
- Institute for Applied Physics, Eberhard Karls University of Tübingen and Center LISA+, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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17
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Horrer A, Krieg K, Freudenberger K, Rau S, Leidner L, Gauglitz G, Kern DP, Fleischer M. Plasmonic vertical dimer arrays as elements for biosensing. Anal Bioanal Chem 2015; 407:8225-31. [PMID: 26345439 DOI: 10.1007/s00216-015-8974-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 08/05/2015] [Accepted: 08/12/2015] [Indexed: 11/28/2022]
Abstract
Localized surface plasmon resonances of metallic nanoparticles can be used for biosensing because of their sensitive dependence on the refractive index of the surrounding medium. The binding of molecules to the particles causes a change of the effective refractive index in their close vicinity, which leads to a reversible shift of the resonance. We present simulations and sensing experiments of a plasmon resonance based biosensor that makes use of the narrow antisymmetric resonance in coupled plasmonic vertical dimers. The sensitivity of the antisymmetric resonance is compared with that of a surface lattice resonance for refractive index sensing of bulk and of thin layers of molecules. The functionality of such a sensor surface is demonstrated via a testosterone immunoassay for detection of antibody from a solution by binding to surface-immobilized antigen in a fluidic channel.
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Affiliation(s)
- Andreas Horrer
- Institute for Applied Physics and Center LISA+, University of Tübingen, Auf der Morgenstelle 10, 72076, Tübingen, Germany.
| | - Katrin Krieg
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Kathrin Freudenberger
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Sabrina Rau
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Lothar Leidner
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Günter Gauglitz
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Dieter P Kern
- Institute for Applied Physics and Center LISA+, University of Tübingen, Auf der Morgenstelle 10, 72076, Tübingen, Germany
| | - Monika Fleischer
- Institute for Applied Physics and Center LISA+, University of Tübingen, Auf der Morgenstelle 10, 72076, Tübingen, Germany.
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18
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Schäfer C, Kern DP, Fleischer M. Capturing molecules with plasmonic nanotips in microfluidic channels by dielectrophoresis. Lab Chip 2015; 15:1066-1071. [PMID: 25519221 DOI: 10.1039/c4lc01018c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Over the last decades, different concepts have been established for the use of plasmonic nanostructures in sensing applications. One challenge in this context lies in delivering the analyte of interest to the location of the nanostructures and selectively attaching it to their surfaces. Here we present a method for the collection and concentration of molecules on arrays of metallic nanocones, making use of the high electric field gradients at the nanotips. For this purpose, the nanocones are integrated into a microfluidic channel and used as nanoelectrodes. By applying an AC voltage, dielectrophoresis is used to capture molecules from the channel region near the nanocones. Simulations of the dielectrophoretic forces in the channel are presented as well as experimental proof of the proposed method. After attachment of the molecules, optical read-out techniques can directly be performed on the plasmonic nanostructures.
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Affiliation(s)
- Christian Schäfer
- Eberhard Karls Universität Tübingen, Institute for Applied Physics and Center LISA+, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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19
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Reichenbach P, Horneber A, Gollmer DA, Hille A, Mihaljevic J, Schäfer C, Kern DP, Meixner AJ, Zhang D, Fleischer M, Eng LM. Nonlinear optical point light sources through field enhancement at metallic nanocones. Opt Express 2014; 22:15484-501. [PMID: 24977808 DOI: 10.1364/oe.22.015484] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A stable nonlinear optical point light source is investigated, based on field enhancement at individual, pointed gold nanocones with sub-wavelength dimensions. Exciting these cones with near-infrared, focused radially polarized femtosecond beams allows for tip-emission at the second harmonic wavelength (second harmonic generation, SHG) in the visible range. In fact, gold nanocones with ultra-sharp tips possess interesting nonlinear optical (NLO) properties for SHG and two-photon photoluminescence (TPPL) emission, due to the enhanced electric field confinement at the tip apex combined with centrosymmetry breaking. Using two complementary optical setups for bottom or top illumination a sharp tip SHG emission is discriminated from the broad TPPL background continuum. Moreover, comparing the experiments with theoretical calculations manifests that these NLO signatures originate either from the tip apex or the base edge of the nanocones, clearly depending on the cone size, the surrounding medium, and illumination conditions. Finally, it is demonstrated that the tip-emitted signal vanishes when switching from radial to azimuthal polarization.
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20
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Horrer A, Schäfer C, Broch K, Gollmer DA, Rogalski J, Fulmes J, Zhang D, Meixner AJ, Schreiber F, Kern DP, Fleischer M. Parallel fabrication of plasmonic nanocone sensing arrays. Small 2013; 9:3987-4088. [PMID: 24302595 DOI: 10.1002/smll.201300449] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Indexed: 06/02/2023]
Abstract
A fully parallel approach for the fabrication of arrays of metallic nanocones and triangular nanopyramids is presented. Different processes utilizing nanosphere lithography for the creation of etch masks are developed. Monolayers of spheres are reduced in size and directly used as masks, or mono- and double layers are employed as templates for the deposition of aluminum oxide masks. The masks are transferred into an underlying gold or silver layer by argon ion milling, which leads to nanocones or nanopyramids with very sharp tips. Near the tips the enhancement of an external electromagnetic field is particularly strong. This fact is confirmed by numerical simulations and by luminescence imaging in a confocal microscope. Such localized strong fields can amongst others be utilized for high-resolution, high-sensitivity spectroscopy and sensing of molecules near the tip. Arrays of such plasmonic nanostructures thus constitute controllable platforms for surface-enhanced Raman spectroscopy. A thin film of pentacene molecules is evaporated onto both nanocone and nanopyramid substrates, and the observed Raman enhancement is evaluated.
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Affiliation(s)
- Andreas Horrer
- Institute for Applied Physics and Center LISA[+], Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
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21
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Schäfer C, Gollmer DA, Horrer A, Fulmes J, Weber-Bargioni A, Cabrini S, Schuck PJ, Kern DP, Fleischer M. A single particle plasmon resonance study of 3D conical nanoantennas. Nanoscale 2013; 5:7861-7866. [PMID: 23846476 DOI: 10.1039/c3nr01292a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Metallic nanocones are well-suited optical antennas for near-field microscopy and spectroscopy, exhibiting a number of different plasmonic modes. A major challenge in using nanocones for many applications is maximizing the signal at the tip while minimizing the background from the base. It is shown that nanocone plasmon resonance properties can be shifted over a wide range of wavelengths by variation of the substrate, material, size and shape, enabling potential control over specific modes and field distributions. The individual resonances are identified and studied by correlated single particle dark field scattering and scanning electron microscopy in combination with numerical simulations.
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Affiliation(s)
- Christian Schäfer
- Eberhard Karls Universität Tübingen, Institute for Applied Physics and Center LISA+, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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22
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Schneeweiss P, Gierling M, Visanescu G, Kern DP, Judd TE, Günther A, Fortágh J. Dispersion forces between ultracold atoms and a carbon nanotube. Nat Nanotechnol 2012; 7:515-519. [PMID: 22706699 DOI: 10.1038/nnano.2012.93] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 05/08/2012] [Indexed: 06/01/2023]
Abstract
Dispersion forces are long-range interactions between polarizable objects that arise from fluctuations in the electromagnetic field between them. Dispersion forces have been observed between microscopic objects such as atoms and molecules (the van der Waals interaction), between macroscopic objects (the Casimir interaction) and between an atom and a macroscopic object (the Casimir-Polder interaction). Dispersion forces are known to increase the attractive forces between the components in nanomechanical devices, to influence adsorption rates onto nanostructures, and to influence the interactions between biomolecules in biological systems. In recent years, there has been growing interest in studying dispersion forces in nanoscale systems and in exploring the interactions between carbon nanotubes and cold atoms. However, there are considerable difficulties in developing dispersion force theories for general, finite geometries such as nanostructures. Thus, there is a need for new experimental methods that are able to go beyond measurements of planar surfaces and nanoscale gratings and make measurements on isolated nanostructures. Here, we measure the dispersion force between a rubidium atom and a multiwalled carbon nanotube by inserting the nanotube into a cloud of ultracold rubidium atoms and monitoring the loss of atoms from the cloud as a function of time. We perform these experiments with both thermal clouds of ultracold atoms and with Bose-Einstein condensates. The results obtained with this approach will aid the development of theories describing quantum fields near nanostructures, and hybrid cold-atom/solid-state devices may also prove useful for applications in quantum sensing and quantum information.
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Affiliation(s)
- P Schneeweiss
- CQ Center for Collective Quantum Phenomena and their Applications, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
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23
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Prati E, De Michielis M, Belli M, Cocco S, Fanciulli M, Kotekar-Patil D, Ruoff M, Kern DP, Wharam DA, Verduijn J, Tettamanzi GC, Rogge S, Roche B, Wacquez R, Jehl X, Vinet M, Sanquer M. Few electron limit of n-type metal oxide semiconductor single electron transistors. Nanotechnology 2012; 23:215204. [PMID: 22552118 DOI: 10.1088/0957-4484/23/21/215204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report the electronic transport on n-type silicon single electron transistors (SETs) fabricated in complementary metal oxide semiconductor (CMOS) technology. The n-type metal oxide silicon SETs (n-MOSSETs) are built within a pre-industrial fully depleted silicon on insulator (FDSOI) technology with a silicon thickness down to 10 nm on 200 mm wafers. The nominal channel size of 20 × 20 nm(2) is obtained by employing electron beam lithography for active and gate level patterning. The Coulomb blockade stability diagram is precisely resolved at 4.2 K and it exhibits large addition energies of tens of meV. The confinement of the electrons in the quantum dot has been modeled by using a current spin density functional theory (CS-DFT) method. CMOS technology enables massive production of SETs for ultimate nanoelectronic and quantum variable based devices.
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Affiliation(s)
- Enrico Prati
- Laboratorio MDM, CNR-IMM, Via Olivetti 2, I-20864 Agrate Brianza, Italy.
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24
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Gierling M, Schneeweiss P, Visanescu G, Federsel P, Häffner M, Kern DP, Judd TE, Günther A, Fortágh J. Cold-atom scanning probe microscopy. Nat Nanotechnol 2011; 6:446-451. [PMID: 21623359 DOI: 10.1038/nnano.2011.80] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 04/21/2011] [Indexed: 05/30/2023]
Abstract
Scanning probe microscopes are widely used to study surfaces with atomic resolution in many areas of nanoscience. Ultracold atomic gases trapped in electromagnetic potentials can be used to study electromagnetic interactions between the atoms and nearby surfaces in chip-based systems. Here we demonstrate a new type of scanning probe microscope that combines these two areas of research by using an ultracold gas as the tip in a scanning probe microscope. This cold-atom scanning probe microscope offers a large scanning volume, an ultrasoft tip of well-defined shape and high purity, and sensitivity to electromagnetic forces (including dispersion forces near nanostructured surfaces). We use the cold-atom scanning probe microscope to non-destructively measure the position and height of carbon nanotube structures and individual free-standing nanotubes. Cooling the atoms in the gas to form a Bose-Einstein condensate increases the resolution of the device.
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Affiliation(s)
- M Gierling
- CQ Center for Collective Quantum Phenomena and their Applications, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany
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25
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Fleischer M, Weber-Bargioni A, Altoe MVP, Schwartzberg AM, Schuck PJ, Cabrini S, Kern DP. Gold nanocone near-field scanning optical microscopy probes. ACS Nano 2011; 5:2570-2579. [PMID: 21401116 DOI: 10.1021/nn102199u] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Near-field scanning optical microscopy enables the simultaneous topographical and subdiffraction limited optical imaging of surfaces. A process is presented for the implementation of single individually engineered gold cones at the tips of atomic force microscopy cantilevers. These cantilevers act as novel high-performance optical near-field probes. In the fabrication, thin-film metallization, electron beam induced deposition of etch masks, and Ar ion milling are combined. The cone constitutes a well-defined highly efficient optical antenna with a tip radius on the order of 10 nm and an adjustable plasmon resonance frequency. The sharp tip enables high resolution topographical imaging. By controllably varying the cone size, the resonance frequency can be adapted to the application of choice. Structural properties of these sharp-tipped probes are presented together with topographical images recorded with a cone probe. The antenna functionality is demonstrated by gathering the near-field enhanced Raman signature of individual carbon nanotubes with a gold cone scanning probe.
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Affiliation(s)
- Monika Fleischer
- Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
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26
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Abstract
Fourier transform x-ray holography has been used to image gold test objects with submicrometer structure, resolving features as small as 60 nanometers. The hologram-recording instrument uses coherent 3.4-nanometer radiation from the soft x-ray undulator beamline X1A at the National Synchrotron Light Source. The specimen to be imaged is placed near the first-order focal spot produced by a Fresnel zone plate; the other orders, chiefly the zeroth, illuminate the specimen. The wave scattered by the specimen interferes with the spherical reference wave from the focal spot, forming a hologram with fringes of low spatial frequency. The hologram is recorded in digital form by a charge-coupled device camera, and the specimen image is obtained by numerical reconstruction.
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27
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Fleischer M, Zhang D, Braun K, Jäger S, Ehlich R, Häffner M, Stanciu C, Hörber JKH, Meixner AJ, Kern DP. Tailoring gold nanostructures for near-field optical applications. Nanotechnology 2010; 21:065301. [PMID: 20057031 DOI: 10.1088/0957-4484/21/6/065301] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A method of combined thin-film deposition, electron beam lithography, and ion milling is presented for the fabrication of gold and silver nanostructures. The flexibility of lithographical processes for the variation of geometric parameters is combined with three-dimensional control over the surface evolution. Depending on the etching angle, different shapes ranging from cones over rods to cups can be achieved. These size- and shape-tunable structures present a toolbox for nano-optical investigations. As an example, optical properties of systematically varying structures are examined in a parabolic mirror confocal microscope.
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Affiliation(s)
- M Fleischer
- Institute of Applied Physics, Eberhard Karls Universität Tübingen, Tübingen, Germany.
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28
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Abstract
The controlled placement of DNA molecules onto solid surfaces is the first step in the fabrication of DNA arrays. The sequential deposition of tiny drops containing the probe DNA fragments using arrays of spotting needles or ink jet nozzles has become a standard. However, a caveat of liquid spotting is the drying of the deposited drop because this creates the typical inhomogeneities, i.e., rims around the spot. Another drawback is that each DNA array is an original and has to be fabricated individually. Microcontact printing is a versatile technique to place proteins onto different target surfaces in uniformly patterned monolayers with high lateral resolution. Here, we show for the first time that DNA can also be printed with equally high resolution in the submicrometer range using an elastomeric stamp with chemically tailored surface. Two regimes for the transfer of the molecules were observed. Finally, microcontact printing of an array of DNA probes onto a solid support and its use in a subsequent hybridization assay was demonstrated.
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29
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Hansen W, Smith TP, Lee KY, Brum JA, Knoedler CM, Hong JM, Kern DP. Zeeman bifurcation of quantum-dot spectra. Phys Rev Lett 1989; 62:2168-2171. [PMID: 10039873 DOI: 10.1103/physrevlett.62.2168] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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30
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Affiliation(s)
- Dieter P. Kern
- IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598
| | - Thomas F. Kuech
- IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598
| | | | - Al Wagner
- IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598
| | - Dean E. Eastman
- IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598
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31
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Smith TP, Lee KY, Hong JM, Knoedler CM, Arnot H, Kern DP. Fractional quantization in ultranarrow electron channels. Phys Rev B Condens Matter 1988; 38:1558-1561. [PMID: 9946428 DOI: 10.1103/physrevb.38.1558] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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32
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Smith TP, Lee KY, Knoedler CM, Hong JM, Kern DP. Electronic spectroscopy of zero-dimensional systems. Phys Rev B Condens Matter 1988; 38:2172-2175. [PMID: 9946510 DOI: 10.1103/physrevb.38.2172] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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