Characteristics of gate-all-around silicon nanowire field effect transistors with asymmetric channel width and source/drain doping concentration

We performed 3D simulations to demonstrate structural effects in sub-20 nm gate-all-around silicon nanowire field effect transistors having asymmetric channel width along the channel direction. We analyzed the differences in the electrical and physical properties for various slopes of the channel width in asymmetric silicon nanowire field effect transistors (SNWFETs) and compared them to symmetrical SNWFETs with uniform channel width. In the same manner, the effects of the individual doping concentration at the source and drain also have been investigated. For various structural conditions, the current and switching characteristics are seriously affected. The differences attributed to the doping levels and geometric conditions are due to the electric field and electron density profile. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745858]ope

Spontaneous reduction of metal ions on the sidewalls of carbon nanotubes

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An investigation of the mechanisms of electronic sensing of protein adsorption on carbon nanotube devices

It has been reported that protein adsorption on single-walled carbon nanotube field effect transistors (FETs) leads to appreciable changes in the electrical conductance of the devices, a phenomenon that can be exploited for label-free detection of biomolecules with a high potential for miniaturization. This work presents an elucidation of the electronic biosensing mechanisms with a newly developed microarray of nanotube "micromat" sensors. Chemical functionalization schemes are devised to block selected components of the devices from protein adsorption, self-assembled monolayers (SAMS) of methoxy(poly-(ethylene glycol))thiol (mPEG-SH) on the metal electrodes (Au, Pd) and PEG-containing surfactants on the nanotubes. Extensive characterization reveals that electronic effects occurring at the metal-nanotube contacts due to protein adsorption constitute a more significant contribution to the electronic biosensing signal than adsorption solely along the exposed lengths of the nanotubes.X11406439sciescopu

Generation of Reactive Oxygen Species from Silicon Nanowires

Processing and synthesis of purified nanomaterials of diverse composition, size, and properties is an evolving process. Studies have demonstrated that some nanomaterials have potential toxic effects and have led to toxicity research focusing on nanotoxicology. About two million workers will be employed in the field of nanotechnology over the next 10 years. The unknown effects of nanomaterials create a need for research and development of techniques to identify possible toxicity. Through a cooperative effort between National Institute for Occupational Safety and Health and IBM to address possible occupational exposures, silicon-based nanowires (SiNWs) were obtained for our study. These SiNWs are anisotropic filamentary crystals of silicon, synthesized by the vapor-liquid-solid method and used in bio-sensors, gas sensors, and field effect transistors. Reactive oxygen species (ROS) can be generated when organisms are exposed to a material causing cellular responses, such as lipid peroxidation, H 2 O 2 production, and DNA damage. SiNWs were assessed using three different in vitro environments (H 2 O 2 , RAW 264.7 cells, and rat alveolar macrophages) for ROS generation and possible toxicity identification. We used electron spin resonance, analysis of lipid peroxidation, measurement of H 2 O 2 production, and the comet assay to assess generation of ROS from SiNW and define possible mechanisms. Our results demonstrate that SiNWs do not appear to be significant generators of free radicals

Pulmonary Toxicity, Distribution, and Clearance of Intratracheally Instilled Silicon Nanowires in Rats

Silicon nanowires (Si NWs) are being manufactured for use as sensors and transistors for circuit applications. The goal was to assess pulmonary toxicity and fate of Si NW using an in vivo experimental model. Male Sprague-Dawley rats were intratracheally instilled with 10, 25, 50, 100, or 250 μg of Si NW (~20–30 nm diameter; ~2–15 μm length). Lung damage and the pulmonary distribution and clearance of Si NW were assessed at 1, 3, 7, 28, and 91 days after-treatment. Si NW treatment resulted in dose-dependent increases in lung injury and inflammation that resolved over time. At day 91 after treatment with the highest doses, lung collagen was increased. Approximately 70% of deposited Si NW was cleared by 28 days with most of the Si NW localized exclusively in macrophages. In conclusion, Si NW induced transient lung toxicity which may be associated with an early rapid particle clearance; however, persistence of Si NW over time related to dose or wire length may lead to increased collagen deposition in the lung