Plasmon scattering from holes: from single hole scattering to Young's experiment

In this article, the scattering of surface plasmon polaritons (SPPs) into photons at holes is investigated. A local, electrically excited source of SPPs using a scanning tunnelling microscope (STM) produces an outgoing circular plasmon wave on a thick (200 nm) gold film on glass containing holes of 250, 500 and 1000 nm diameter. Fourier plane images of the photons from hole-scattered plasmons show that the larger the hole diameter, the more directional the scattered radiation. These results are confirmed by a model where the hole is considered as a distribution of horizontal dipoles whose relative amplitudes, directions, and phases depend linearly on the local SPP electric field. An SPP-Young's experiment is also performed, where the STM-excited SPP-wave is incident on a pair of 1 $\mu$m diameter holes in the thick gold film. The visibility of the resulting fringes in the Fourier plane is analyzed to show that the polarization of the electric field is maintained when SPPs scatter into photons. From this SPP-Young's experiment, an upper bound of $\approx$ 200 nm for the radius of this STM-excited source of surface plasmon polaritons is determined

Luminescence induite par microscopie à effet tunnel et étude des propriétés électroniques, chimiques et optiques de la surface de carbure de silicium 6H-SiC(0001)3x3

Le microscope à effet tunnel (STM) permet une analyse spatiale et spectroscopique de surfaces à l'échelle atomique. Mise en évidence peu après l invention du STM, la lumière émise par la jonction tunnel contient des informations pertinentes sur les propriétés électroniques et optiques de surfaces ou de nano-objets.La thématique dans laquelle s'inscrit cette thèse est la luminescence induite par STM sur substrat semiconducteur à large bande interdite. Les travaux ont porté sur la reconstruction de surface SiC(0001)3x3 du carbure de silicium (SiC) et s'articulent autour de trois parties.La première partie est consacrée à l'étude de la luminescence de la jonction tunnel métal/vide/SiC(0001)3x3. Cette étude, en parallèle à des mesures de spectroscopie tunnel, a mis en évidence les mécanismes et propriétés de transport électronique le long des états de surface du SiC.Une deuxième partie est dédiée à l'adsorption de molécules organiques sur la surface SiC(0001)3x3. La fonctionnalisation organique du SiC est une étape indispensable pour l étude de molécules individuelles mais aussi pour la conception de matériaux hybrides organique/inorganique. La résolution submoléculaire du STM associée à des calculs ab initio en collaboration ont dégagé un modèle de chimisorption détaillé de la phthalocyanine hydrogénée.La dernière partie décrit des simulations numériques, basées sur le formalisme des tenseurs de Green, de la lumière émise par la jonction tunnel. Ces travaux ont permis de modéliser d'une part l'influence de la forme de la pointe du STM sur le spectre de la lumière émise, d'autre part l'inhibition de la fluorescence de molécules individuelles excitées par STM.The scanning tunnelling microscope (STM) enables both spatial and spectroscopic investigations of surfaces at the atomic scale. Light emission by the tunnel junction was demonstrated not long after the STM invention and contains valuable information on the electronic and optical properties of surfaces and nano-objects. The theme of this thesis is the induced light emission in STM experiments on wide band gap semiconductors. The results were obtained on the SiC(0001)3x3 silicon carbide (SiC) surface and are divided into three parts. The first part considers the light emission from the metal/vacuum/SiC(0001)3x3 junction of the STM. This study, associated with tunnelling spectroscopy measurements, provided a deep insight into the mechanisms and properties of electronic transport along the SiC surface states. The second part deals with the adsorption of individual organic molecules on SiC(0001)3x3. Organic functionalization is a necessary step not only for the study of single molecule fluorescence with the STM but also for the conception of organic/inorganic hybrid materials. The submolecular STM resolution and DFT calculations carried out in collaboration enabled a detailed understanding of the adsorption configuration of phthalocyanine molecules and give some general characteristics of molecules susceptible to anchor on this surface. The third part is devoted to numerical simulations, based on the Green tensor technique, of the light emission from the tunnel junction. This model showed the influence of the STM tip geometry on the far-field emitted light and also the fluorescence enhancement and quenching of single molecules excited by STM.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Émission de lumière sous la pointe d’un microscope à effet tunnel

Une source de lumière de dimension atomique est réalisée à l’aide d’un microscope à effet tunnel (STM). Cette source de photons est localisée à la jonction entre une pointe, que l’on peut déplacer avec une précision atomique, et un échantillon métallique. Elle se distingue par une excitation de nature électronique (le courant tunnel), et fait également intervenir des plasmons de surface présents dans la jonction tunnel. La jonction tunnel est ainsi une « source électrique » de plasmons de surface. Cependant, on est encore loin de comprendre le fonctionnement de cette source optique et plasmonique et d’en avoir exploité toutes les possibilités

Molecular ligands guide individual nanocrystals to a soft-landing alignment on surfaces

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Molecular ligands guide individual nanocrystals to a soft-landing alignment on surfaces

International audienc

Manipulation of cadmium selenide nanorods with an atomic force microscope

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The mechanism of light emission from a scanning tunnelling microscope operating in air

International audienceThe scanning tunnelling microscope (STM) may be used as a low-energy, electrical nanosource of surface plasmon polaritons and light. In this article, we demonstrate that the optimum mode of operation of the STM for maximum photon emission is completely different in air than in vacuum. To this end, we investigate the emission of photons, the variation in the relative tip-sample distance and the measured current as a function of time for an STM operating in air. Contrary to the case of an STM operating in vacuum, the measured current between the tip and sample for an STM in air is very unstable (rapidly fluctuating in time) when the applied voltage between the tip and sample is in the ∼1.5–3 V range (i.e., in the energy range of visible photons). The photon emission occurs in short (50 μs) bursts when the STM tip is closest to the sample. The current instabilities are shown to be a key ingredient for producing intense light emission from an STM operating in air (photon emission rate several orders of magnitude higher than for stable current). These results are explained in terms of the interplay between the tunnel current and the electrochemical current in the ubiquitous thin water layer that exists when working in air