110 research outputs found
Optical microcavity with semiconducting single-wall carbon nanotubes
We report studies of optical Fabry-Perot microcavities based on
semiconducting single-wall carbon nanotubes with a quality factor of 160. We
experimentally demonstrate a huge photoluminescence signal enhancement by a
factor of 30 in comparison with the identical film and by a factor of 180 if
compared with a thin film containing non-purified (8,7) nanotubes. Futhermore,
the spectral full-width at half-maximum of the photo-induced emission is
reduced down to 8 nm with very good directivity at a wavelength of about 1.3
m. Such results prove the great potential of carbon nanotubes for photonic
applications
Passivating Properties of Hydrogenated Amorphous Silicon Carbide Deposited by PECVD Technique for Photovoltaic Applications
AbstractAmorphous hydrogenated silicon carbide (a-SiCx:H) could be used as a passivating layer in solar cell configuration. We have deposited a-SiCx:H by plasma enhanced CVD on polished silicon wafers. Si-rich a-SiCx:H allows to reach a surface recombination velocity of 7.5cm.s-1. The hydrogenation of silicon surface dangling bonds and the electricalfield-effect near the interface are analyzed by minority carrier lifetime and C(V) measurements and additional FTIR and XPS spectroscopy. The fixed charges within the layers are found to be amphoteric. The interface trap density increases with carbon content in a-SiCx:H because of a lower hydrogen content at the a-SiCx:H/Si interface. The polarity of the fixed charge is depending on the presence of a metallic contact. As a-SiCx:H may be considered as a semiconductor, the a-SiCx:H/c-Si interface is in inversion regime at equilibrium inducing a band bending and accu- mulation when adding a metallic contact
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
Optical Gain in Carbon Nanotubes
Semiconducting single-wall carbon nanotubes (s-SWNTs) have proved to be
promising material for nanophotonics and optoelectronics. Due to the
possibility of tuning their direct band gap and controlling excitonic
recombinations in the near-infrared wavelength range, s-SWNT can be used as
efficient light emitters. We report the first experimental demonstration of
room temperature intrinsic optical gain as high as 190 cm-1 at a wavelength of
1.3 {\mu}m in a thin film doped with s-SWNT. These results constitute a
significant milestone toward the development of laser sources based on carbon
nanotubes for future high performance integrated circuits.Comment: 4 figure
Plasmonic enhancement of SERS measured on molecules in carbon nanotubes
We isolated the plasmonic contribution to surface-enhanced Raman scattering (SERS) and found it to be much stronger than expected. Organic dyes encapsulated in single-walled carbon nanotubes are ideal probes for quantifying plasmonic enhancement in a Raman experiment. The molecules are chemically protected through the nanotube wall and spatially isolated from the metal, which prevents enhancement by chemical means and through surface roughness. The tubes carry molecules into SERS hotspots, thereby defining molecular position and making it accessible for structural characterization with atomic-force and electron microscopy. We measured a SERS enhancement factor of 106 on α-sexithiophene (6T) molecules in the gap of a plasmonic nanodimer. This is two orders of magnitude stronger than predicted by the electromagnetic enhancement theory (104). We discuss various phenomena that may explain the discrepancy (including hybridization, static and dynamic charge transfer, surface roughness, uncertainties in molecular position and orientation), but found all of them lacking in enhancement for our probe system. We suggest that plasmonic enhancement in SERS is, in fact, much stronger than currently anticipated. We discuss novel approaches for treating SERS quantum mechanically that appear promising for predicting correct enhancement factors. Our findings have important consequences on the understanding of SERS as well as for designing and optimizing plasmonic substrates
- …