A study of microminiaturized devices for bioastronautical monitoring or analysis Quarterly report

Analog digital filters, converters, and microminiaturized circuits for bioastronautical applicatio

Interference effects in electronic transport through metallic single-wall carbon nanotubes

In a recent paper Liang {\it et al.} [Nature {\bf 411}, 665 (2001)] showed experimentally, that metallic nanotubes, strongly coupled to external electrodes, may act as coherent molecular waveguides for electronic transport. The experimental results were supported by theoretical analysis based on the scattering matrix approach. In this paper we analyze theoretically this problem using a real-space approach, which makes it possible to control quality of interface contacts. Electronic structure of the nanotube is taken into account within the tight-binding model. External electrodes and the central part (sample) are assumed to be made of carbon nanotubes, while the contacts between electrodes and the sample are modeled by appropriate on-site (diagonal) and hopping (off-diagonal) parameters. Conductance is calculated by the Green function technique combined with the Landauer formalism. In the plots displaying conductance {\it vs.} bias and gate voltages, we have found typical diamond structure patterns, similar to those observed experimentally. In certain cases, however, we have found new features in the patterns, like a double-diamond sub-structure.Comment: 15 pages, 4 figures. To apear in Phys. Rev.

Electron transport in semiconducting carbon nanotubes with hetero-metallic contacts

We present an atomistic self-consistent study of the electronic and transport properties of semiconducting carbon nanotube in contact with metal electrodes of different work functions, which shows simultaneous electron and hole doping inside the nanotube junction through contact-induced charge transfer. We find that the band lineup in the nanotube bulk region is determined by the effective work function difference between the nanotube channel and source/drain electrodes, while electron transmission through the SWNT junction is affected by the local band structure modulation at the two metal-nanotube interfaces, leading to an effective decoupling of interface and bulk effects in electron transport through nanotube junction devices.Comment: Higher quality figures available at http://www.albany.edu/~yx15212

A study of microminiaturized devices for bioastronautical monitoring or analysis Research report, 1 Mar. 1969 - 31 Mar. 1970

Microminiaturized devices for bioastronautical monitoring or analysi

Ramsar Policy Brief No. 5. Restoring drained peatlands: A necessary step to achieve global climate goals

Peatlands cover about 400 million hectares (ha), or 3% of the land surface of our planet. Yet they store more carbon, more effectively and for longer periods, than any other ecosystem on land. Intact peatlands also provide essential ecosystem services such as regulating water cycles, purifying water, and supporting a wealth of biodiversity. Since peat is hidden below ground, it is often unrecognised and can be damaged unknowingly. New, large peatland areas are still being discovered including forest-covered peatlands in the tropics. Around 50 million ha of peatlands globally are currently drained and have been transformed to grazing land, forestry land and cropland, used for peat extraction or impacted by infrastructure. These drained peatlands are responsible for approximately 4% (2 Gt CO2 -eq/year) of all anthropogenic greenhouse gas emissions. Achieving the climate goals of the Paris Agreement requires protection of all remaining intact peatland and rapid restoration of almost all drained peatlands. This will also contribute to delivering the Sustainable Development Goals (SDGs), in particular SDG 6, Target 6.6, on protecting and restoring water related ecosystems and SDG 15, Targets 15.1, on conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services, as well as 15.5 on reducing degradation of natural habitats. The United Nations Decade on Ecosystem Restoration 2021-2030 provides the opportunity to rapidly scale up efforts

Conductance of Distorted Carbon Nanotubes

We have calculated the effects of structural distortions of armchair carbon nanotubes on their electrical transport properties. We found that the bending of the nanotubes decreases their transmission function in certain energy ranges and leads to an increased electrical resistance. Electronic structure calculations show that these energy ranges contain localized states with significant $\sigma$-$\pi$ hybridization resulting from the increased curvature produced by bending. Our calculations of the contact resistance show that the large contact resistances observed for SWNTs are likely due to the weak coupling of the NT to the metal in side bonded NT-metal configurations.Comment: 5 pages RevTeX including 4 figures, submitted to PR

Enhanced thermal stability and spin-lattice relaxation rate of N@C60 inside carbon nanotubes

We studied the temperature stability of the endohedral fullerene molecule, N@C60, inside single-wall carbon nanotubes using electron spin resonance spectroscopy. We found that the nitrogen escapes at higher temperatures in the encapsulated material as compared to its pristine, crystalline form. The temperature dependent spin-lattice relaxation time, T_1, of the encapsulated molecule is significantly shorter than that of the crystalline material, which is explained by the interaction of the nitrogen spin with the conduction electrons of the nanotubes.Comment: 5 pages, 4 figures, 1 tabl

High on-off conductance switching ratio in light-driven self-assembled molecular devices

Date du colloque : 5-9/01/2010International audienc

Reversible Band Gap Engineering in Carbon Nanotubes by Radial Deformation

We present a systematic analysis of the effect of radial deformation on the atomic and electronic structure of zigzag and armchair single wall carbon nanotubes using the first principle plane wave method. The nanotubes were deformed by applying a radial strain, which distorts the circular cross section to an elliptical one. The atomic structure of the nanotubes under this strain are fully optimized, and the electronic structure is calculated self-consistently to determine the response of individual bands to the radial deformation. The band gap of the insulating tube is closed and eventually an insulator-metal transition sets in by the radial strain which is in the elastic range. Using this property a multiple quantum well structure with tunable and reversible electronic structure is formed on an individual nanotube and its band-lineup is determined from first-principles. The elastic energy due to the radial deformation and elastic constants are calculated and compared with classical theories.Comment: To be appear in Phys. Rev. B, Apr 15, 200