Catalytic growth of single-wall carbon nanotubes from metal particles

The invention provides an assembly of novel nanotube devices that can be employed in a variety of applications. In particular, the nanotube devices of the present invention provide a new class of versatile chemical and biological sensors. The device includes a nanotube (20) disposed between two catalyst islands (21) on a substrate (22). Two metal electrodes (23) are made to fully cover respective catalyst islands, including the two ends (24) of the bridging nanotube.

Carbon nanotube devices

Apparatus and methods according to the present invention preferably utilize electroosmotic pumps that are capable of generating high pressure and flow without moving mechanical parts and the associated generation of unacceptable electrical and acoustic noise, as well as the associated reduction in reliability. These electroosmotic pumps are preferably fabricated with materials and structures that improve performance, efficiency, and reduce weight and manufacturing cost relative to presently available micropumps. These electroosmotic pumps also preferably allow for recapture of evolved gases and deposited materials, which may provide for long-term closed-loop operation. Apparatus and methods according to the present invention also allow active regulation of the temperature of the device through electrical control of the flow through the pump and can utilize multiple cooling loops to allow independent regulation of the special and temporal characteristics of the device temperature profiles. Novel microchannel structures are also described.

Electroosmotic microchannel cooling system

Nanotube films and articles and methods of making the same are disclosed. A conductive article includes an aggregate of nanotube segments in which the nanotube segments contact other nanotube segments to define a plurality of conductive pathways along the article. The nanotube segments may be single walled carbon nanotubes, or multi-walled carbon nanotubes. The various segments may have different lengths and may include segments having a length shorter than the length of the article. The articles so formed may be disposed on substrates, and may form an electrical network of nanotubes within the article itself. Conductive articles may be made on a substrate by forming a nanotube fabric on the substrate, and defining a pattern within the fabric in which the pattern corresponds to the conductive article. The nanotube fabric may be formed by growing the nanotube fabric on the substrate using a catalyst, for example, in which the catalyst is a gas phase catalyst, or in which the catalyst is a metallic gas phase catalyst. The nanotube fabric may be formed by depositing a solution of suspended nanotubes on the substrate. The deposited solution may be spun to create a spin-coating of the solution. The solution may be deposited by dipping the substrate into the solution. The nanotube fabric is formed by spraying an aerosol having nanotubes onto a surface of the substrate.

Methods of nanotube films and articles

A field emission device having bundles of aligned parallel carbon nanotubes on a substrate. The carbon nanotubes are oriented perpendicular to the substrate. The carbon nanotube bundles may be up to 300 microns tall, for example. The bundles of carbon nanotubes extend only from regions of the substrate patterned with a catalyst material. Preferably, the catalyst material is iron oxide. The substrate is preferably porous silicon, as this produces the highest quality, most well-aligned nanotubes. Smooth, nonporous silicon or quartz can also be used as the substrate. The method of the invention starts with forming a porous layer on a silicon substrate by electrochemical etching. Then, a thin layer of iron is deposited on the porous layer in patterned regions. The iron is then oxidized into iron oxide, and then the substrate is exposed to ethylene gas at elevated temperature. The iron oxide catalyzes the formation of bundles of aligned parallel carbon nanotubes which grow perpendicular to the substrate surface. The height of the nanotube bundles above the substrate is determined by the duration of the catalysis step. The nanotube bundles only grow from the patterned regions.

Self-oriented bundles of carbon nanotubes and method of making same

Electron field emission devices (cold cathodes), vacuum microelectronic devices and field emission displays which incorporate cold cathodes and methods of making and using same. More specifically, cold cathode devices comprising electron emitting structures grown directly onto a substrate material. The invention also relates to patterned precursor substrates for use in fabricating field emission devices and methods of making same and also to catalytically growing other electronic structures, such as films, cones, cylinders, pyramids or the like, directly onto substrates.

Carbon fiber-based field emission devices

An element with elongated, high aspect ratio channels (30) such as microchannel plate is fabricated by electrochemical etching of a p-type silicon element (10) in a electrolyte (26) to form channels extending through the element. The electrolyte may be an aqueous electrolyte. For use as a microchannel plate, the silicon surfaces of the channels can be converted to insulating silicon dioxide (28), and a dynode material (32) with a high electron emissivity can be deposited onto the insulating surfaces of the channels. New dynode materials are also disclosed.

Silicon etching process for making microchannel plates

Microchannel plates (MCP) fabricated from standard silicon wafer substrates using a novel silicon micromachining process, together with standard silicon photolithographic process steps, are described. The resulting SiMCP microchannels have dimensions of ∼0.5 to ∼25 μm, with aspect ratios up to 300, and have the dimensional precision and absence of interstitial defects characteristic of photolithographic processing, compatible with positional matching to silicon electronics readouts. The open channel areal fraction and detection efficiency may exceed 90% on plates up to 300 mm in diameter. The resulting silicon substrates can be converted entirely to amorphous quartz (qMCP). The strip resistance and secondary emission are developed by controlled depositions of thin films, at temperatures up to 1200°C, also compatible with high-temperture brazing, and can be essentially hydrogen, water and radionuclide-free. Novel secondary emitters and cesiated photocathodes can be high-temperature deposited or nucleated in the channels or the first strike surface. Results on resistivity, secondary emission and gain are presented.

Silicon-micromachined microchannel plates

A static magnetic memory includes a layer having a plurality of vertically oriented and shape-anisotropic elongated ferromagnetic particles. A plurality of writing conductors are adjacent the layer, and the conductors selectively apply magnetic fields to selected regions of the layer by directing electrical current to magnetize the particles in an up or down direction. Static reading means detect the direction of magnetization. The particles may include a soft magnet portion and a hard magnet portion. In another preferred embodiment, a material and a method of making same includes providing a matrix full of elongated holes, depositing a first magnetic material having a first coercivity into the holes, and then depositing a second magnetic material having a second coercivity into the holes to form a composite elongated particle in each hole.

Magnetic memory having shape anisotropic magnetic elements

A microdynode electron multiplier provides numerous microchannels extending parallel to one another through a layered structure (20) incorporating insulating spacer layers (38) and dynode layers (36) which either incorporate a conductive electrode layer (54) or are contiguous with a conductive electrode layer. The dynode layers include materials with high electron emissivity. The dynode layers can be biased to different electrical potentials to provide a potential gradient along the length of each microchannel. Multi-stage electron multiplication provides high gain. The device desirably is formed as a monolithic, sealed structure with a cathode structure (26) such as a photocathode and an anode structure (28). The device can provide a multi pixel imaging device of extremely high sensitivity and resolution.

Robert W. Boerstler

Papers

Carbon fiber-based field emission devices

Silicon etching process for making microchannel plates

Silicon-micromachined microchannel plates

Magnetic memory having shape anisotropic magnetic elements

Microdynode integrated electron multiplier