26 research outputs found
Charge transport in a single superconducting tin nanowire encapsulated in a multiwalled carbon nanotube
The charge transport properties of single superconducting tin nanowires,
encapsulated by multiwalled carbon nanotubes have been investigated by
multi-probe measurements. The multiwalled carbon nanotube protects the tin
nanowire from oxidation and shape fragmentation and therefore allows us to
investigate the electronic properties of stable wires with diameters as small
as 25 nm. The transparency of the contact between the Ti/Au electrode and
nanowire can be tuned by argonion etching the multiwalled nanotube. Application
of a large electrical current results in local heating at the contact which in
turn suppresses superconductivity
Carbon Nanotubes Encapsulating Superconducting Single-Crystalline Tin Nanowires
Superconducting low dimensional systems are the natural choice for fast and sensitive infrared detection, because of their quantum nature and the low-noise, cryogenic operation environment. On the other hand, monochromatic and coherent electron beams, emitted from superconductors and carbon-based nanostructured materials, respectively, are significant for the development of electron optical systems such as electron microscopes and electron-beam nanofabrication systems. Here we describe for the first time a simple method which yields carbon nanotubes encapsulating single crystalline superconducting tin nanowires by employing the catalytic chemical vapor deposition method over solid tin dioxide. The superconducting tin nanowires, with diameters 15-35 nm, are covered with well-graphitized carbon walls and show, due to their reduced diameters, a critical magnetic field (Hc) more than 30 times higher than the value of bulk metallic tin.
Carbon Nanotubes Encapsulating Superconducting Single-Crystalline Tin Nanowires. Nano Lett
ABSTRACT Superconducting low dimensional systems are the natural choice for fast and sensitive infrared detection, because of their quantum nature and the low-noise, cryogenic operation environment. On the other hand, monochromatic and coherent electron beams, emitted from superconductors and carbon-based nanostructured materials, respectively, are significant for the development of electron optical systems such as electron microscopes and electron-beam nanofabrication systems. Here we describe for the first time a simple method which yields carbon nanotubes encapsulating single crystalline superconducting tin nanowires by employing the catalytic chemical vapor deposition method over solid tin dioxide. The superconducting tin nanowires, with diameters 15−35 nm, are covered with well-graphitized carbon walls and show, due to their reduced diameters, a critical magnetic field (H c ) more than 30 times higher than the value of bulk metallic tin. The hot-electron phenomena in low-dimensional superconducting systems are of fundamental importance for high energy resolution bolometers. 1 Photon absorption in a superconducting detector creates an avalanche electron charge, 2 or 3 orders of magnitude higher than that in a semiconductor for the same photon energy. This results in an enhanced resolution in energy-resolving devices, such as superconducting tunnel junctions, 2 and extends the range of detectable energies
STCHIOMETRIE, STRUCTURE ET TENUE EN CHAMP ELECTRIQUE D'UN FILM ULTRA MINCE DE NBO X 1 SUR NB(110)
CHATENAY MALABRY-Ecole centrale (920192301) / SudocSudocFranceF
Electronic properties probed by scanning tunneling spectroscopy: From isolated gold nanocrystal to well-defined supracrystals
International audienceScanning tunneling microscopy and spectroscopy at 5 K have been used to determine the electronic properties of 7-nm dodecanethiol-passivated Au nanocrystals in three different configurations: isolated nanocrystal, self-organized thin films (few nanocrystal layers), and large three-dimensional well-defined thick films (over 30 nanocrystal layers) called supracrystals. The electronic properties of both thin and thick well-ordered supracrystals are analyzed in scanning tunneling spectroscopy geometry through dI/dV curves and conductance mapping at different bias voltages. The single particles exhibit a typical dI/dV curve with a Coulomb gap of similar to 360 meV and a Coulomb staircase. The dI/dV curve of the thin supracrystals presents a Coulomb blockade feature similar to 100 meV narrower in width than that of the single nanocrystal but without well-defined staircase. On the contrary, the thick supracrystals exhibit a dI/dV curve showing a large Coulomb gap with a Coulomb-staircase-like structure. Generally, the conductance mapping is found to be very homogeneous for both supracrystals. Nevertheless, for some bias voltages, inhomogeneities across individual nanocrystals appear. Additionally, some of these inhomogeneities seem to be related to the supracrystal surface morphology. Finally, these slight variations in the conductance mapping across individual nanocrystals embedded in the supracrystal are discussed in terms of high degree of nanocrystal ordering, low nanocrystal size distribution, and nanocrystal crystallinity
Star-shaped ethynylpyrimidine with long alkoxyl side chains: synthesis, fluorescence and 2D self-assembling
International audienceIn this contribution, we describe the synthesis of a star shaped ethynylpyrimidine having long alkoxyl side chains using Suzuki cross-coupling reactions. This compound presents interesting blue light emission fluorescence as well as self-assembling properties on graphite: a chiral system is obtained starting from a nonchiral molecule. This preliminary work indicates that pyrimidine derivatives could be good candidates for the development of novel functional organic materials
Hydrophilic Gold Supracrystals Differing by the Nanoparticle Crystalline Structure
Very
few studies concern water-soluble nanocrystals self-assembled
in crystalline 3D superlattices called supracrystals. Furthermore,
the control of the crystalline structure of nanocrystals known as
nanocrystallinity has not been yet achieved with water-soluble nanocrystals.
Here we produce, selectively, 5 nm Au single-domain (SD) and polycrystalline
(POLY) water-soluble nanocrystals. These nanocrystals self-assembled
in face-centered-cubic (fcc) supracrystals. The supracrystal stiffness
evolves with the nanocrystallinity, the nanocrystal surface charge,
as well as the steric effect of the coating agent. The optical properties
of SD and POLY nanoparticles and those of the related supracrystals
are also presented. In addition, a nanocrystallinity segregation event
was observed upon drying-assisted self-assembly of aqueous stoichiometric
mixtures of SD and POLY NCs, as in the case of their hydrophobic counterparts
Modulating Physical Properties of Isolated and Self-Assembled Nanocrystals through Change in Nanocrystallinity
For self-assembled nanocrystals in three-dimensional (3D) superlattices, called supracrystals, the crystalline structure of the metal nanocrystals (either single domain or polycrystalline) or nanocrystallinity is likely to induce significant changes in the physical properties. Previous studies demonstrated that spontaneous nanocrystallinity segregation takes place in colloidal solution upon self-assembling of 5 nm dodecanethiol-passivated Au nanocrystals. This segregation allows the exclusive selection of single domain and polycrystalline nanoparticles and consequently producing supracrystals with these building blocks. Here, we investigate the influence of nanocrystallinity on different properties of nanocrystals with either single domain or polycrystalline structure. In particular, the influence of nanocrystallinity on the localized surface plasmon resonance of individual nanocrystals dispersed in the same dielectric media is reported. Moreover, the frequencies of the radial breathing mode of single domain and polycrystalline nanoparticles are measured. Finally, the orientational ordering of single domain nanocrystals markedly changes the supracrystal elastic moduli compared to supracrystals of polycrystalline nanocrystals
Assessing the relevance of building block crystallinity for tuning the stiffness of gold nanocrystal superlattices
International audienceWe study the influence of the size and nanocrystallinity of dodecanethiol-coated gold nanocrystals (NCs) on the stiffness of 3D self-assembled NC superlattices (called supracrystals). Using single domain and polycrystalline NCs as building blocks for supracrystals, it is shown that the stiffness of supracrystals can be tuned upon change in relative amounts of single and polycrystalline NCs
Mechanical Properties of Au Supracrystals Tuned by Flexible Ligand Interactions
Here mechanical properties of face
cubic centered colloidal crystals obtained out of equilibrium by solvent
evaporation of coated Au nanocrystals suspension, called supracrystals,
are reported as a function ligand chain length (<i>n</i>) and interparticle edge-to-edge distance within the supracrystals
(δ<sub>pp</sub>) for two nanocrystal sizes (<i>d</i>). Young’s modulus (<i>E</i>*) and hardness (<i>H</i>) are independent of δ<sub>pp</sub> and of the supracrystal
morphology. Both <i>E</i>* and <i>H</i> are in
the range of few tenths of a MPa to a few GPa. Tuning of δ<sub>pp</sub> by 50% is achieved by controlling the solvent vapor pressure
(<i>P</i><sub>t</sub>) during the evaporation process. For
any nanocrystal size, at <i>P</i><sub>t</sub> = 0, <i>E</i>* and <i>H</i> values markedly increase with
increasing <i>n</i> from 12 to 14. At <i>P</i><sub>t</sub> = 39% and 75%, such dependency disappears. This trend
differs from classical nanocomposite materials and is attributed to
a change in the conformation of flexible ligands with <i>n</i> and to free thiol-containing molecules trapped in the supracrystal
lattices