Search results for " Tunnel"
showing 10 items of 477 documents
Electron tunneling from colloidal CdSe quantum dots to ZnO nanowires studied by time-resolved luminescence and photoconductivity experiments
2015
CdSe quantum dots (QDs) with different organic linker molecules are attached to ZnO nanowires (NWs) to study the luminescence dynamics and the electron tunneling from the QDs to the nanowires in time-resolved photoluminescence (PL) and photoconductivity measurements. The PL transients of the QD luminescence indicate two different recombination channels: the direct recombination inside the QD core and the recombination via QD surface defect states. After linking the QDs to the ZnO NW surface, photo-induced electron tunneling from an excited state of the QD into the conduction band of the nanowire becomes visible by a clear decrease of the PL decay time. Efficient electron tunneling is confir…
Isolated Mn-12 single-molecule magnets grafted on gold surfaces via electrostatic interactions
2005
Electrostatic interactions drive the adsorption of polycationic single-molecule magnets onto anionic monolayers self-assembled on gold surfaces. Well-isolated magnetic clusters have been deposited and characterized using scanning tunneling microscopy and X-ray photoemission spectroscopy.
Interlayer exciton dynamics in van der Waals heterostructures
2019
Atomically thin transition metal dichalcogenides can be stacked to van der Waals heterostructures enabling the design of new materials with tailored properties. The strong Coulomb interaction gives rise to interlayer excitons, where electrons and holes are spatially separated in different layers. In this work, we reveal the time- and momentum-dependent elementary processes behind the formation, thermalization and photoemission of interlayer excitons for the exemplary MoSe2–WSe2 heterostructure. We identify tunneling of holes from MoSe2 to WSe2 on a ps timescale as the crucial process for interlayer exciton formation. We also predict a drastic reduction of the formation time as a function of…
Theory of quantum-circuit refrigeration by photon-assisted electron tunneling
2017
We focus on a recently experimentally realized scenario of normal-metal-insulator-superconductor tunnel junctions coupled to a superconducting resonator. We develop a first-principles theory to describe the effect of photon-assisted electron tunneling on the quantum state of the resonator. Our results are in very good quantitative agreement with the previous experiments on refrigeration and heating of the resonator using the photon-assisted tunneling, thus providing a stringent verification of the developed theory. Importantly, our results provide simple analytical estimates of the voltage-tunable coupling strength and temperature of the thermal reservoir formed by the photon-assisted tunne…
Tailoring the transmittance of integrated optical waveguides with short metallic nanoparticle chains
2004
We study the ability of noble metal nanoparticle chains supporting localized surface plasmons to tailor the transmittance of channel waveguides on which they are deposited. The optical interaction between a microwaveguide ~MWG! and various arrangements of nanoparticles is first analyzed by means numerical calculations based on the Green’s tensor formalism. For specific geometries of the particle chains, the transmission spectra of the composite device ~MWG and nanoparticles! exhibits strong modulations in the optical range with the appearance of a neat band gap. The results of an experiment inspired by this theoretical study are also discussed. The photon scanning tunneling microscope image…
Submicrometer in-plane integrated surface plasmon cavities.
2007
International audience; The optical properties of in-plane integrated surface plasmon polariton (SPP) cavities comprised of a thin film area sandwiched between two one-dimensional Bragg SPP mirrors are investigated numerically and experimentally. We discuss the resonance condition of these cavities, and we analyze in details the physical origin of the dispersion of this resonance. On the basis of numerical results, we show that in-plane SPP cavities can be used to achieve local SPP field enhancement and antireflecting SPP layers. The numerical results are compared to near-field optical images recorded by operating a photon scanning tunneling microscope. From the near-field images recorded o…
Nonlinear photon-assisted tunneling transport in optical gap antennas.
2014
International audience; We introduce strongly coupled optical gap antennas to interface optical radiation with current-carrying electrons at the nanoscale. The transducer relies on the nonlinear optical and electrical properties of an optical gap antenna operating in the tunneling regime. We discuss the underlying physical mechanisms controlling the conversion involving d-band electrons and demonstrate that a simple two-wire optical antenna can provide advanced optoelectronic functionalities beyond tailoring the electromagnetic response of a single emitter. Interfacing an electronic command layer with a nanoscale optical device may thus be facilitated by the optical rectennas discussed here.
Squeezing the Optical Near-Field Zone by Plasmon Coupling of Metallic Nanoparticles
1999
We report on the experimental observation of near-field optical effects close to Au nanoparticles using a photon scanning tunneling microscope (PSTM). Constant height operation of the PSTM allowed an unprecedented direct comparison with theoretical computations of the distribution of the optical near-field intensity. An unexpected squeezing of the optical near field due to plasmon coupling was observed above a chain of Au nanoparticles.
Imaging standing surface plasmons by photon tunneling
2005
We present a direct method for optically exciting and imaging delocalized standing surface plasmons in thin metal films. We show theoretically that when imaging the field of the plasmons with a photon scanning tunneling microscope, the presence of the dielectric probe has a negligible effect on the surface modes of the metal film. We demonstrate that plasmon interference can be sustained in arbitrarily large regions of the metal film in comparison to the excitation wavelength. This knowledge can be important when seeking the relative distance between two scattering centers such as the presence of micron or submicron structures.
Optical Near-Field Properties of Lithographically Designed Metallic Nanoparticles
1999
ABSTRACTWe report on the experimental observation of localized surface plasmons sustained by small metallic particles using a photon scanning tunneling microscope (PSTM). The surface plasmons are excited in gold nanostructures tailored by electron beam lithography. The constant height operation of the PSTM allowed a direct comparison with theoretical computations of the distribution of the optical near-field intensity. Plasmon coupling above a chain of Au particles and electromagnetic energy transfer from a resonantly excited nanoparticle to a nanowire are demonstrated. Our experimental results appear to be in good agreement with theoretical computations based on the Green's Dyadic Techniqu…