43 research outputs found
Light Emission in Silicon from Carbon Nanotubes
The use of optics in microelectronic circuits to overcome the limitation of
metallic interconnects is more and more considered as a viable solution. Among
future silicon compatible materials, carbon nanotubes are promising candidates
thanks to their ability to emit, modulate and detect light in the wavelength
range of silicon transparency. We report the first integration of carbon
nanotubes with silicon waveguides, successfully coupling their emission and
absorption properties. A complete study of this coupling between carbon
nanotubes and silicon waveguides was carried out, which led to the
demonstration of the temperature-independent emission from carbon nanotubes in
silicon at a wavelength of 1.3 {\mu}m. This represents the first milestone in
the development of photonics based on carbon nanotubes on silicon
Quantum capacitance governs electrolyte conductivity in carbon nanotubes
In recent experiments, unprecedentedly large values for the conductivity of
electrolytes through carbon nanotubes (CNTs) have been measured, possibly owing
to flow slip and a high pore surface charge density whose origin is still
unknown. By accounting for the coupling between the {quantum} CNT and the
{classical} electrolyte-filled pore capacitances, we study the case where a
gate voltage is applied to the CNT. The computed surface charge and
conductivity dependence on reservoir salt concentration and gate voltage are
intimately connected to the CNT electronic density of states. This approach
provides key insight into why metallic CNTs have larger conductivities than
semi-conducting ones
Layering transitions in superfluid helium adsorbed on a carbon nanotube mechanical resonator
Helium is recognized as a model system for the study of phase transitions. Of
particular interest is the superfluid phase in two dimensions. We report
measurements on superfluid helium films adsorbed on the surface of a suspended
carbon nanotube. We measure the mechanical vibrations of the nanotube to probe
the adsorbed helium film. We demonstrate the formation of helium layers up to
five atoms thickness. Upon increasing the vapour pressure, we observe
layer-by-layer growth with discontinuities in both the number of adsorbed atoms
and the speed of sound in the adsorbed film. These hitherto unobserved
discontinuities point to a series of first-order layering transitions. Our
results show that helium multilayers adsorbed on a nanotube are of
unprecedented quality compared to previous works. They pave the way to new
studies of quantized superfluid vortex dynamics on cylindrical surfaces, of the
Berezinskii-Kosterlitz-Thouless phase transition in this new geometry, perhaps
also to supersolidity in crystalline single layers as predicted in quantum
Monte Carlo calculations.Comment: 10 pages, 3 figure
Quantifying the performances of SU-8 microfluidic devices: high liquid water tightness, long-term stability, and vacuum compatibility
Despite several decades of development, microfluidics lacks a sealing
material that can be readily fabricated, leak-tight under high liquid water
pressure, stable over a long time, and vacuum compatible. In this paper, we
report the performances of a micro-scale processable sealing material for
nanofluidic/microfluidics chip fabrication, which enables us to achieve all
these requirements. We observed that micrometric walls made of SU-8
photoresist, whose thickness can be as low as 35 m, exhibit water pressure
leak-tightness from 1.5 bar up to 5.5 bar, no water porosity even after 2
months of aging, and are able to sustain under mbar vacuum. This
sealing material is therefore reliable and versatile for building microchips,
part of which must be isolated from liquid water under pressure or vacuum.
Moreover, the fabrication process we propose does not require the use of
aggressive chemicals or high-temperature or high-energy plasma treatment. It
thus opens a new perspective to seal microchips where delicate surfaces such as
nanomaterials are present
00 [Material grĂĄfico]
Copia digital. Madrid : Ministerio de EducaciĂłn, Cultura y Deporte, 201
Photonique hybride des nanotubes de carbone
On-chip optical communication may increase drastically performances and consumption of communication systems. Indeed, optical channels do not face limitations that metallics interconnects do. Even better would be the achievable data rate due to the multiplexing possibility in optics. In order to keep compatibility with electronic devices, optical components and interconnects should be built in silicon. However, this material is not suitable for some optical function, such as laser sources. Thus, there is a need to integrate alternative materials to compensate for silicon weaknesses. My PhD work focuses on integration of carbon nanotube on silicon for photonics applications. In this work, potential use of carbon nanotube for light emission function is investigated. First, I will propose clue to understand the appearance of optical gain in semiconducting carbon nanotube. Such investigation is done by mean of pump-probe experiments, where the excitons lifetimes are measured. Those lifetimes slightly increase while centrifugation time and speed is increased, during the extraction process. A possible explanation is that defect-free carbon nanotubes are selected by the centrifugation process. In parallel, I worked on designing an efficient method to couple nanotubes photoluminescence with silicon waveguides. This method appears to be quite robust, and allows to observe coupling between the nanotube photoluminescence and the optical mode of the waveguide. In order to obtain a more intense interaction between the optical mode and carbon nanotubes, I investigated the coupling between carbon nanotubes and several photonic cavities, including microdisks, Fabry-PĂ©rot cavities and ring resonators. Specifically, ring resonators allow to measure the photoluminescence of carbon nanotube structured by the resonant modes. Several configurations are studied to understand more in-depth the coupling mechanisms: micro-photoluminescence, guided photoluminescence and integrated photoluminescence.LâintĂ©gration des communications optiques sur puce offre de vastes promesses en termes de performances et de rĂ©duction de la puissance consommĂ©e, les canaux optiques ne souffrant pas des nombreuses limitations des canaux mĂ©talliques. De plus, lâinformation codĂ©e optiquement permet dâatteindre des dĂ©bits de donnĂ©es Ă©levĂ©s par le biais du multiplexage en longueur dâonde. Afin de conserver la compatibilitĂ© avec les composants Ă©lectroniques, les communications et composants optiques doivent sâintĂ©grer dans la filiĂšre silicium. Cependant, ce dernier matĂ©riau ne permet pas dâenvisager la rĂ©alisation de certaines fonctions optiques, en particulier la source laser. Dâautres matĂ©riaux doivent ainsi ĂȘtre intĂ©grĂ©s pour supplĂ©er au silicium. Mes travaux de thĂšse portent sur lâintĂ©gration de nanotubes de carbone sur plate-forme silicium pour la photonique. Dans ces travaux, le potentiel des nanotubes de carbone pour la rĂ©alisation de sources optiques intĂ©grĂ©es est explorĂ©. Dans un premier temps, je proposerai des pistes de comprĂ©hension de lâapparition du gain optique dans les nanotubes de carbone semiconducteurs par analyse des temps de vie des excitons, mesurĂ©s en spectroscopie pompe-sonde. Ces temps de vie sont sensiblement rallongĂ©s lorsque la centrifugation des nanotubes de carbone, au cours de lâextraction, est poussĂ©e Ă des vĂ©locitĂ©s et des temps plus longs. Une explication envisagĂ©e est la rĂ©duction du nombre de dĂ©fauts Ă la surface des nanotubes, ces dĂ©fauts se comportant comme des centres de recombinaison non-radiatifs. Dâautre part, une mĂ©thode efficace dâintĂ©gration des nanotubes de carbone sur guide dâonde silicium a Ă©tĂ© proposĂ©e. Cette mĂ©thode robuste et permet dâobserver le couplage de la photoluminescence des nanotubes de carbone avec le mode optique du guide dâonde. Afin dâobtenir une interaction exaltĂ©e entre mode optique et nanotube de carbone, le couplage entre les nanotubes et diffĂ©rentes cavitĂ©s photoniques, incluant microdisques, cavitĂ©s Fabry-PĂ©rot et micro-rĂ©sonateurs en anneau, a Ă©tĂ© Ă©tudiĂ©. Lâemploi en particulier de rĂ©sonateurs en anneau permet dâobserver la structuration de la photoluminescence des nanotubes de carbone par les modes de rĂ©sonance de lâanneau. DiffĂ©rentes configurations ont Ă©tĂ© Ă©tudiĂ©es afin de complĂ©ter la comprĂ©hension des mĂ©canismes de couplage : micro-photoluminescence, photoluminescence guidĂ©e et photoluminescence intĂ©grĂ©e
Carbon nanotube hybrid photonic
LâintĂ©gration des communications optiques sur puce offre de vastes promesses en termes de performances et de rĂ©duction de la puissance consommĂ©e, les canaux optiques ne souffrant pas des nombreuses limitations des canaux mĂ©talliques. De plus, lâinformation codĂ©e optiquement permet dâatteindre des dĂ©bits de donnĂ©es Ă©levĂ©s par le biais du multiplexage en longueur dâonde. Afin de conserver la compatibilitĂ© avec les composants Ă©lectroniques, les communications et composants optiques doivent sâintĂ©grer dans la filiĂšre silicium. Cependant, ce dernier matĂ©riau ne permet pas dâenvisager la rĂ©alisation de certaines fonctions optiques, en particulier la source laser. Dâautres matĂ©riaux doivent ainsi ĂȘtre intĂ©grĂ©s pour supplĂ©er au silicium. Mes travaux de thĂšse portent sur lâintĂ©gration de nanotubes de carbone sur plate-forme silicium pour la photonique. Dans ces travaux, le potentiel des nanotubes de carbone pour la rĂ©alisation de sources optiques intĂ©grĂ©es est explorĂ©. Dans un premier temps, je proposerai des pistes de comprĂ©hension de lâapparition du gain optique dans les nanotubes de carbone semiconducteurs par analyse des temps de vie des excitons, mesurĂ©s en spectroscopie pompe-sonde. Ces temps de vie sont sensiblement rallongĂ©s lorsque la centrifugation des nanotubes de carbone, au cours de lâextraction, est poussĂ©e Ă des vĂ©locitĂ©s et des temps plus longs. Une explication envisagĂ©e est la rĂ©duction du nombre de dĂ©fauts Ă la surface des nanotubes, ces dĂ©fauts se comportant comme des centres de recombinaison non-radiatifs. Dâautre part, une mĂ©thode efficace dâintĂ©gration des nanotubes de carbone sur guide dâonde silicium a Ă©tĂ© proposĂ©e. Cette mĂ©thode robuste et permet dâobserver le couplage de la photoluminescence des nanotubes de carbone avec le mode optique du guide dâonde. Afin dâobtenir une interaction exaltĂ©e entre mode optique et nanotube de carbone, le couplage entre les nanotubes et diffĂ©rentes cavitĂ©s photoniques, incluant microdisques, cavitĂ©s Fabry-PĂ©rot et micro-rĂ©sonateurs en anneau, a Ă©tĂ© Ă©tudiĂ©. Lâemploi en particulier de rĂ©sonateurs en anneau permet dâobserver la structuration de la photoluminescence des nanotubes de carbone par les modes de rĂ©sonance de lâanneau. DiffĂ©rentes configurations ont Ă©tĂ© Ă©tudiĂ©es afin de complĂ©ter la comprĂ©hension des mĂ©canismes de couplage : micro-photoluminescence, photoluminescence guidĂ©e et photoluminescence intĂ©grĂ©e.On-chip optical communication may increase drastically performances and consumption of communication systems. Indeed, optical channels do not face limitations that metallics interconnects do. Even better would be the achievable data rate due to the multiplexing possibility in optics. In order to keep compatibility with electronic devices, optical components and interconnects should be built in silicon. However, this material is not suitable for some optical function, such as laser sources. Thus, there is a need to integrate alternative materials to compensate for silicon weaknesses. My PhD work focuses on integration of carbon nanotube on silicon for photonics applications. In this work, potential use of carbon nanotube for light emission function is investigated. First, I will propose clue to understand the appearance of optical gain in semiconducting carbon nanotube. Such investigation is done by mean of pump-probe experiments, where the excitons lifetimes are measured. Those lifetimes slightly increase while centrifugation time and speed is increased, during the extraction process. A possible explanation is that defect-free carbon nanotubes are selected by the centrifugation process. In parallel, I worked on designing an efficient method to couple nanotubes photoluminescence with silicon waveguides. This method appears to be quite robust, and allows to observe coupling between the nanotube photoluminescence and the optical mode of the waveguide. In order to obtain a more intense interaction between the optical mode and carbon nanotubes, I investigated the coupling between carbon nanotubes and several photonic cavities, including microdisks, Fabry-PĂ©rot cavities and ring resonators. Specifically, ring resonators allow to measure the photoluminescence of carbon nanotube structured by the resonant modes. Several configurations are studied to understand more in-depth the coupling mechanisms: micro-photoluminescence, guided photoluminescence and integrated photoluminescence