The underlying physics of the application of low-temperature, low-pressure reactive plasmas in various nanoassembly processes is described. From the viewpoint of the ``cause and effect'' approach, this Colloquium focuses on the benefits and challenges of using plasma-based systems in nanofabrication of nanostructured silicon films, low-dimensional semiconducting quantum structures, ordered carbon nanotip arrays, highly crystalline ${\mathrm{TiO}}_{2}$ coatings, and nanostructured hydroxyapatite bioceramics. Other examples and future prospects of plasma-aided nanofabrication are also discussed.

/pdf/colloquium-reactive-plasmas-as-a-versatile-nanofabrication-41yd8l1e03.pdf

Colloquium: Reactive plasmas as a versatile nanofabrication tool

The radiation resistance of organic electro-optic and optoelectronic materials for space applications is receiving increased attention. An earlier investigation reported that guest-host poled polymer EO modulator devices composed of a phenyltetraene bridge-type chromophore in amorphous polycarbonate (CLD/APC) did not exhibit a decrease in EO response (i.e., an increase in modulation-switching voltage- V) following irradiation by low dose [10-160 krad(Si)] 60Co gamma-rays. To provide further evidences to the observed radiation stability, the post-irradiation responses of 60Co gamma-rays on CLD1/APC thin films are examined by various chemical and spectroscopic methods including: a solubility test, thin-layer chromatography, proton nuclear magnetic resonance spectroscopy, UV-vis absorption, and infra-red absorption. The results indicate that CLD1 and APC did not decompose under gamma-ray irradiation at dose levels ranging from 66-274 krad(Si) and from 61-154 krad(Si), respectively which support the previously reported data.

Radiation resistance of a gamma-ray irradiated nonlinear optic chromophore

We have recently developed a nanocomposite based on polyhedral oligomeric silsesquixoane for medical device application for particular use in a microvascular network. Using spectroscopic analyses, we characterised the polymer before subjecting it to both in vitro and in vivo degradation. In the same setting, the foreign- body reaction of this polymer was determined. An in vitro feasibility study as to the efficacy of neo-endothelialisation was then performed. Next, the anti-thrombogenic nature of the nanocomposite was elicited. Based on the favourable outcomes of these experiments, nanocomposite microvessels were designed and fabricated to form the components of a microvascular network. Our results indicate that silsesquioxane is an optimal building material for microvascular grafts. This therefore constitutes the foundation on which we intend to construct an in vitro artificial capillary bed model.

Development of silsesquioxane-polyurethane nanocomposites for use in microvascular networks.

The development of nanocircuits for space applications is an emerging technology area for NASA. We will preset our recent research results on the performance of both nanomaterials and actively running nanocircuits during heavy ion irradiation. The radiation experiments were performed at the National Superconducting Cyclotron Laboratory at Michigan State University whose available primary beams and beam energies well match the energy spectra of abundant charged particles in galactic cosmic rays. Primary beams of Krypton having mass numbers of 78 and 86 respectively were used in two sets of experiments, representative of the high-Z heavy ions encountered in a space radiation environment.

/pdf/performance-of-nanomaterials-and-actively-running-12g3mhjn3o.pdf

Performance of Nanomaterials and Actively Running Nanocircuits During Heavy Ion Irradiation

Materials for space application

We report the formation of silicon and carbon hetero-nanostructures in an inductively coupled plasma system by a simultaneous growth/etching mechanism. Multi-walled carbon nanotubes were grown during one, three and five hour depositions, while tapered silicon nanowires were progressively etched. The carbon and silicon nanostructures and the interfaces between them were studied by electron microscopies and micro Raman spectroscopies. The potential of this method for large-scale controlled production of nano heterostructures without the requirement of a common catalyst is explored.

/pdf/new-hetero-silicon-carbon-nanostructure-formation-mechanism-24ia19rr3x.pdf

New hetero silicon-carbon nanostructure formation mechanism.

This paper reports the results of two separate heavy ion irradiation experiments. In the first set, nanomaterial samples including single and multi wall carbon nanotubes and electrospun carbon nanofibers, with well-graphitized vapor grown carbon fibers as controls, were irradiated using a primary beam of Krypton-86 ions at 142 Amp MeV. The single and multi wall carbon nanotube samples sustained little damage from the highest radiation dose. In the second set, a gallium nitride nanowire-based field effect transistor was irradiated using a primary beam of Krypton-78 ions at 140 Amp MeV. The nanocircuit maintained normal function under high active bias and high radiation dose. Krypton-86 and Krypton-78 are representative of high-Z heavy ions encountered in a space radiation environment. Results from the pre-irradiation structure and optoelectronic characterization of the gallium nitride nanowires are also reported.

S. P. Song

Papers

New hetero silicon-carbon nanostructure formation mechanism.

Nanotube, nanowire, and nanocircuit behavior in simulated space environments