Ronald J. Tonucci

Nanochannel Array Glass

The fabrication and characterization of a glass containing a regular parallel array of submicrometer channels or capillaries are described. The capillaries are arranged in a two-dimensional hexagonal close packing configuration with channel diameters as small as 33 nanometers and packing densities as high as 3 x 1010 channels per square centimeter. The high-temperature stability of the nanochannel glass array is well suited as a host or template for the formation of quantum confined semiconductor structures or as a mask for massively parallel patterned lithographic applications.

Nanochannel Glass Replica Membranes

The preparation of thin metallic membranes containing uniform, patterned voids with diameters as small as 40 nanometers and packing densities greater than 3 × 109 voids per square centimeter is described. These membranes, made of platinum, gold, tungsten, and molybdenum, have been fabricated by thin-film deposition with nanochannel glass wafers as substrates. The membranes are well suited for use as masks in substrate patterning applications such as ion implantation, reactive ion etching, and materials deposition. Results are presented on their use in the parallel patterning of silicon by direct materials deposition with features in the 100-nanometer size regime.

Towards environmental toxicogenomics — development of a flow-through, high-density DNA hybridization array and its application to ecotoxicity assessment

Assessment of the environmental hazard posed by soils/sediments containing low to moderate levels of contaminants using standard analytical chemical methods is uncertain due (in part) to a lack of information on contaminant bioavailability, the unknown interactive effects of contaminant mixtures, our inability to determine the species of a metal in an environmental matrix, and the relative sensitivity of bioassay species. Regulatory agencies compensate for this uncertainty by lowering cleanup goals, but in this process they effectively exclude otherwise attractive cleanup options (i.e. bioremediation). Direct evaluations of soil and sediment toxicity preclude uncertainty from most of these sources. However, the time and cost of chronic toxicity tests limits their general application to higher levels of tiered toxicity assessments. Transcriptional level (mRNA) toxicity assessments offer great advantages in terms of speed, cost and sample throughput. These advantages are currently offset by questions about the environmental relevance of molecular level responses. To this end a flow-through, high-density DNA hybridization array (genosensor) system specifically designed for environmental risk assessment was developed. The genosensor is based on highly regular microchannel glass wafers to which gene probes are covalently bound at discrete (200-microm diameter spot) and addressable (250-microm spot pitch) locations. The flow-through design enables hybridization and washing times to be reduced from approximately 18 h to 20 min. The genosensor was configured so that DNA from 28 environmental samples can be simultaneously hybridized with up to 64 different gene probes. The standard microscopic slide format facilitates data capture with most automated array readers and, thus high sample throughput (> 350 sample/h). In conclusion, hardware development for molecular analysis is enabling very tractable means for analyzing RNA and DNA. These developments have underscored the need for further developmental work in probe design software, and the need to relate transcriptional level data to whole-organism toxicity indicators.

Materials Characterization and Nanofabrication Methods—Nanochannel Glass Materials

Nanochannel glass materials have the potential for numerous nanophotonic applications. Features as small as 10 nm can be created in an optically transparent glass matrix, in a large array format. Complex patterns can also be generated. The ability to fabricate complex optical structures at the nanoscale enables opportunities for new device fabrication and an ability to explore optical interactions at dimensions on the order of a wavelength or smaller. The fabrication, characterization and utility of nanochannel glass materials will be described.

Advances in thin film photonics: materials, science, and technology

Control of refractive index in amorphous silicon materials is investigated. Elementary waveguide structures were prepared on two micron thick amorphous silicon by photon lithographic patterning of a silver masking layer. Hydrogen was implanted at fluence of ~5×1017 cm2 for three energies, 50, 100 and 175 KeV yielding a total does of ~1.5×1018 cm2 consistent with a 10% increase in atoms due to the hydrogen addition. The optical properties of the implanted and non-implanted regions were probed as a function of low temperature annealing. The optical band gap shift to higher energy was consistent with hydrogen addition. Some darkening, absorption increase, were noted on the implanted regions. However, low temperature annealing is known to remove dangling bond damage in amorphous silicon. Prospects of utilizing these waveguides to probe light induced optical changes in amorphous silicon is described as well as the prospects of more advanced devices.

Photorefractive nanocrystalline silicon: materials, science, and application

In recent years the prospect of engineering an integrated photonic technology based on amorphous silicon-based has focused efforts on providing a unified understanding of the optical properties of this material. From a optical properties prospective the science of amorphous silicon is most transparent from a nano-crystalline material framework. Of particular interest for photonic engineering is the tunable range of the refractive index in amorphous silicon, the fast and slow light induced changes in epsilon 1 and 2, the means by which to deposit films of sufficient thickness and smoothness for the photonic application and the relationships among deposition conditions, material properties, and in particular the optical parameters. The present work reviews some of the previous work and examines the experimental and theoretical basis for the fast light induced refractive index change with the hope of providing the insight needed for device engineering. This work suggests several novel designs for light amorphous silicon based light valves and other devices.

Planned experiment to measure the superfluid density of confined4He near Tλ

An experiment using Helmholtz resonator techniques is proposed to measure the effects of confinement on the superfluid density in4He near the lambda point. Recent experimental and technological innovations afford the opportunity of dramatically improving previous measurements. We will exploit recent high resolution thermometry techniques which provide a resolution of the lambda point to within 10−9 K. In addition, the development of glass channel arrays with less than a one percent deviation throughout the entire array and high packing densities will provide a containment sample that is much improved over previous work. Finally, we will employ a high resolution pressure sensor with a SQUID readout to detect the small signal associated with a close approach to the transition.