Showing papers on "Fabrication published in 2002"

Ink-jet printed nanoparticle microelectromechanical systems

Abstract: Reports a method to additively build three-dimensional (3-D) microelectromechanical systems (MEMS) and electrical circuitry by ink-jet printing nanoparticle metal colloids. Fabricating metallic structures from nanoparticles avoids the extreme processing conditions required for standard lithographic fabrication and molten-metal-droplet deposition. Nanoparticles typically measure 1 to 100 nm in diameter and can be sintered at plastic-compatible temperatures as low as 300/spl deg/C to form material nearly indistinguishable from the bulk material. Multiple ink-jet print heads mounted to a computer-controlled 3-axis gantry deposit the 10% by weight metal colloid ink layer-by-layer onto a heated substrate to make two-dimensional (2-D) and 3-D structures. We report a high-Q resonant inductive coil, linear and rotary electrostatic-drive motors, and in-plane and vertical electrothermal actuators. The devices, printed in minutes with a 100 /spl mu/m feature size, were made out of silver and gold material with high conductivity,and feature as many as 400 layers, insulators, 10:1 vertical aspect ratios, and etch-released mechanical structure. These results suggest a route to a desktop or large-area MEMS fabrication system characterized by many layers, low cost, and data-driven fabrication for rapid turn-around time, and represent the first use of ink-jet printing to build active MEMS.

Fabrication of High-Quality Opal Films with Controllable Thickness

Abstract: A dipping method was developed to fabricate three-dimensional colloidal crystal films. The thickness of the films fabricated by this method can be precisely controlled from one layer to several tens of layers by controlling the particle concentration and the film formation speed. Experimental results showed that the spheres form a face-centered cubic structure and that single crystals in the film can extend to centimeter dimensions.

Rare-earth-doped GaN: growth, properties, and fabrication of electroluminescent devices

Abstract: A review is presented of the fabrication, operation, and applications of rare-earth-doped GaN electroluminescent devices (ELDs). GaN:RE ELDs emit light due to impact excitation of the rare earth (RE) ions by hot carriers followed by radiative RE relaxation. By appropriately choosing the RE dopant, narrow linewidth emission can be obtained at selected wavelengths from the ultraviolet to the infrared. The deposition of GaN:RE layers is carried out by solid-source molecular beam epitaxy, and a plasma N/sub 2/ source. Growth mechanisms and optimization of the GaN layers for RE emission are discussed based on RE concentration, growth temperature, and V/III ratio. The fabrication processes and electrical models for both dc- and ac-biased devices are discussed, along with techniques for multicolor integration. Visible emission at red, green, and blue wavelengths from GaN doped with Eu, Er, and Tm has led to the development of flat-panel display (FPD) devices. The brightness characteristics of thick dielectric EL (TDEL) display devices are reviewed as a function of bias, frequency, and time. High contrast TDEL devices using a black dielectric are presented. The fabrication and operation of FPD prototypes are described. Infrared emission at 1.5 /spl mu/m from GaN:Er ELDs has been applied to optical telecommunications devices. The fabrication of GaN channel waveguides by inductively coupled plasma etching is also reviewed, along with waveguide optical characterization.

Fabrication and electrical characteristics of carbon nanotube field emission microcathodes with an integrated gate electrode

Abstract: We report on the fabrication of field emission microcathodes which use carbon nanotubes as the field emission source. The devices incorporated an integrated gate electrode in order to achieve truly low-voltage field emission. A single-mask, self-aligned technique was used to pattern the gate, insulator and catalyst for nanotube growth. Vertically-aligned carbon nanotubes were then grown inside the gated structure by plasma-enhanced chemical vapour deposition. Our self-aligned fabrication process ensured that the nanotubes were always centred with respect to the gate apertures (2 µm diameter) over the entire device. In order to obtain reproducible emission characteristics and to avoid degradation of the device, it was necessary to operate the gate in a pulsed voltage mode with a low duty cycle. The field emission device exhibited an initial turn-on voltage of 9 V. After the first measurements, the turn-on voltage shifted to 15 V, and a peak current density of 0.6 mA cm-2 at 40 V was achieved, using a duty cycle of 0.5%.

Ceramic-embedded micro-electromagnetic device and method of fabrication thereof

Abstract: A micro-electromagnetic device is formed by providing internal channels in a ceramic housing sintered from ceramic materials with high dielectric strength and infiltrating these channels with molten metal. The invention allows the fabrication of arrays of ceramic embedded micro-electromagnetic devices as well as ceramic embedded helical micro-antennas designed for use in the high GHz and THz regions at a fraction of the present cost of manufacturing of such devices and with virtually no restriction to their miniaturization.

Powder metallurgical fabrication processes for NiTi shape memory alloy parts

Abstract: NiTi components with reproducible and stable shape memory properties are attractive for various technical applications (e.g. couplings). With the aim of producing NiTi components on an industrial scale, near-net-shape fabrication routes are preferred considering the limited machinability of NiTi alloys. Powder metallurgy (PM) is known to provide the possibility of material-saving and automated fabrication of at least semi-finished products as well as net-shape components. As promising PM routes hot isostatic pressing (HIP) and metal injection moulding (MIM) were used for the fabrication of NiTi compacts. Microstructural investigations, chemical analysis, X-ray diffraction (XRD) measurements and also differential scanning calometry (DSC) measurements were performed in order to characterize the produced parts. Additionally, the mechanical properties of HIPed samples were measured by tensile tests at room temperature. The components from both fabrication routes show reversible austenite↔martensite transformations which are a prerequisite for shape memory effects.

Tungsten nanowires and their field electron emission properties

Abstract: We report the fabrication of tungsten nanowires, by simple thermal treatment of W films, that behave as self-catalytic layers and their excellent electron field emission properties as well. The obtained nanowires have a diameter ranging from 10 to 50 nm, showing perfect straightness and neat appearance. Typical turn-on field for the electron emission is about 5 V/μm, and the field enhancement factor β becomes 38 256, which is very close to that of the high efficient single-wall carbon nanotube emitters. The most exciting result is the possibility of easy fabrication of perfectly straight nanowires as promising building blocks for terabit-level interconnection and nanomachine components without the intentional use of any heterogeneous catalysts.

Capacitive-type humidity sensors fabricated using the offset lithographic printing process

Abstract: This paper reports on the fabrication of a novel capacitive-type relative humidity sensor of which the electrode films are deposited using the high speed printing process, offset lithography. Parallel-plate capacitor sensor structures have been formed with a number of humidity sensitive polymers including polyimide and polyethersulphone (PES). Details of the fabrication process and sensor characteristics such as linearity, sensitivity and response time are included.

Method for fabrication of field emission devices using carbon nanotube film as a cathode

Abstract: The present invention relates to field emission deices fabrication using carbon nanotube film as a cathode. The multi-wall carbon nanotubes film possesses low electron field emission and high emission current density, which is deposited by catalytic chemical vapor deposition at low temperature. The carbon nanotubes density can be controlled by tuning of the transition metal catalysts in the seed alloy layer. The film can be deposited onto the substrate uniformly with large area. The present invention is related to the fabrication of cold electron sources, florescent light, vacuum electronic devices, field emission displays and methods of making same.

A low-temperature CVD process for silicon carbide MEMS

Abstract: A low-temperature, single precursor CVD process for the realization of SiC-based MEMS and SiC-coated MEMS is described using 1,3-disilabutane. With this deposition method, the fabrication of an all-SiC cantilever beam array is demonstrated using standard microfabrication processes. Also, SiC coating of released Si micromechanical structures is realized using this process. The SiC-coated microstructures are shown to have superior chemical stability when compared to their Si analogs, as well as exhibit highly favorable mechanical properties.

On-chip vacuum microtriode using carbon nanotube field emitters

Abstract: We show a fully integrated, on-chip, vacuum microtriode fabricated via silicon micromachining processes using carbon nanotubes as field emitters. The triode is constructed laterally on a silicon surface using microelectromechanical systems (MEMS) design and fabrication principles. The technique incorporates high-performance nanomaterials in a MEMS design with mature solid-state fabrication technology to create miniaturized, on-chip power amplifying vacuum devices, which could have important and far-reaching scientific and technological implications.

Method of forming semiconductor compound film for fabrication of electronic device and film produced by same

Abstract: A process of forming a compound film includes formulating a nano-powder material with a controlled overall composition and including particles of one solid solution. The nano-powder material is deposited on a substrate (70) to form a layer (52) on the substrate, and the layer is reacted in at least one suitable atmosphere to form the compound film. The compound film may be used in fabrication of a radiation detector or solar cell.

Fabrication of microfluidic devices for AC electrokinetic fluid

Abstract: Two techniques for the fabrication of novel microfluidic devices for electrokinetic fluid pumping are presented. Both consist of forming a micro-channel and reservoirs on a transparent cover sheet and patterning an array of interdigitated asymmetric micro-electrodes on a flat substrate. The two techniques differ from each other in their building materials as well as the pattern replication technique used for the cover sheet fabrication. In the first approach, we used a glass substrate for the electrode fabrication and casting of an elastomer for the cover sheet. In the second approach, both cover sheet and substrate are obtained by imprinting plastic pellets on a pre-patterned or flat mold. In assembled devices, pumping has been demonstrated and characterized by optical microscopy. The observed dependence of the pumping velocity on applied voltage and frequency are in line with theoretical predictions. © 2002 Elsevier Science B.V. All rights reserved.

Fabrication of nanometer-spaced electrodes using gold nanoparticles

Abstract: A simple and highly reproducible technique is demonstrated for the fabrication of metallic electrodes with nanometer separation. Commercially available bare gold colloidal nanoparticles are first trapped between prefabricated large-separation electrodes to form a low-resistance bridge by an ac electric field. A large dc voltage is then applied to break the bridge via electromigration at room temperature, which consistently produces gaps in the sub-10 nm range. The technique is readily applied to prefabricated electrodes with separation up to 1 μm, which can be defined using optical lithography. The simple fabrication scheme will facilitate electronic transport studies of individual nanostructures made by chemical synthesis. As an example, measurement of a thiol-coated gold nanoparticle showing a clear Coulomb staircase is presented.

Thin-film electrochemical devices on fibrous or ribbon-like substrates and method for their manufacture and design

Abstract: The fabrication of functional thin-film patterns, such as solid-state thin-film batteries on substrates (100) having fibrous, or ribbon-like or strip-like geometry is disclosed. Coatings (110,120,130,140 and 150) form a multi-layered and multi-functional battery.

Fabrication of electromagnetic crystals with a complete diamond structure by stereography

Abstract: Three-dimensional electromagnetic or photonic crystals with periodic variations of the dielectric constants were fabricated by a rapid prototyping method called stereolithography. Millimeter-order epoxy lattices with a diamond structure were designed to reflect electromagnetic waves by forming an electromagnetic bandgap in the GHz range. Titanium oxide-based ceramic particles were dispersed into the lattice to control the dielectric constant, resulting in the formation of narrow and deep bandgaps. Crystals of the inverse form that have a network of holes with the diamond structure in a dielectric matrix were successfully fabricated as well. These inverse diamond structures formed the perfect bandgap reflecting electromagnetic waves for all directions. The location of the bandgap agreed with the band calculation using the plane wave propagation method.

High-performance strained Si-on-insulator MOSFETs by novel fabrication processes utilizing Ge-condensation technique

Abstract: Strained SOI (SSOI)-nMOSFETs with enhanced mobility up to 67% were fabricated on a strain-relaxed SiGe-on-insulator substrate using a novel Ge-condensation technique. This method, using only standard Si processes, realizes smooth SSOI surfaces without using SIMOX, wafer bonding, surface polishing or any other special processes. Relaxation ratio of the SiGe substrate was varied from 0% to 100%, resulting in the control of threshold voltage. The Ge-condensation process using conventional SOI substrates is an attractive technique for fabrication of multi-threshold SSOI-CMOS circuits with high current drive.

Nanomechanical resonant structures in silicon nitride: fabrication, operation and dissipation issues

Abstract: We report the fabrication of silicon nitride mechanical devices with lateral dimensions as small as 50 nm. The measured resonant frequencies of these devices (8.5–171 MHz) are the highest reported for silicon nitride structures. We have employed both electrostatic and piezoelectric excitation of these structures. We have also studied the effects of thin metal films on dissipation in these structures and found that the absence of these metal coatings results in a three to four times higher quality factor of the structures.

Fabrication of Polymeric Multimode Waveguides and Devices in SU-8 Photoresist Using Selective Polymerization.

Abstract: Large cross section multimode waveguides have been realized in SU-8 using selective polymerization. SU-8 is a negative photoresist, which has shown good optical properties and it is mechanically and chemically stable. The fabricated waveguides have very smooth sidewalls and exhibit low optical losses. The fabrication method is simple and potentially very cost effective. N x N and 1 x N multimode power splitters have been realized using this fabrication technology.

Thick photoresist development for the fabrication of high aspect ratio magnetic coils

Abstract: This paper reports the fabrication of coils for micro-magnetic devices on silicon using thick photoresists commonly used in the manufacture of microelectromechanical systems. A comparison of three photoresists, EPON SU-8, AZ 4562 and AZ 9260, is presented for the fabrication of high aspect ratio conductors. With a thickness of 81 μm, aspect ratios of 6:1 are obtained using the AZ 9260 photoresist. RF inductors and micro-transformers for power conversion applications are fabricated using this technology. The quality factor of the RF inductors shows maximum values of 23 at 0.4 GHz. Very good measurement is also obtained with the micro-transformers: the resistance of the electroplated copper windings is 0.3 Ω up to 2 MHz.

Characterization of 2219 Aluminum Produced by Electron Beam Freeform Fabrication

Abstract: Researchers at NASA Langley Research Center are developing a new electron beam freeform fabrication (EB F(sup 3)) technique to fabricate metal parts. This process introduces metal wire into a molten pool created by a focused electron beam. Potential aerospace applications for this technology include ground-based fabrication of airframe structures and on-orbit construction and repair of space components and structures. Processing windows for reliably producing high quality 2219 aluminum parts using the EB F(sup 3) technique are being defined. The effects of translation speed, wire feed rate, and beam power on the resulting microstructures and mechanical properties are explored. Tensile properties (ultimate tensile strength, yield strength, and elongation) show little effect over the range of processing conditions tested. Basic processing-microstructure-property correlations are drawn for the EB F(sup 3) process.

Experimental and numerical investigations on microstereolithography of ceramics

Abstract: Microstereolithography (μSL) uses laser light to solidify UV-curable resin mixed with concentrated ceramic powders. During the μSL process, the light scattering from the particle suspension is found to significantly influence the fabrication resolution in both lateral and depth dimensions which are critical for the complex three-dimensional (3D) microfabrication. In this work, we performed Monte Carlo simulations and experimental studies to understand the detailed microscale optical scattering, chemical reaction (polymerization), and their influence on critical fabrication parameters. As a result, it was found that due to the scattering, the fabricated line is wider in width and smaller in depth compared with polymeric fabrication at the same condition. The doping technique that we used substantially reduced the light scattering, which in turn enhanced the fabrication precision and control. In addition, the experimental values of curing depth and radius agreed reasonably well with the theoretical modeling...

Nonlithographic fabrication of lateral superlattices for nanometric electromagnetic-optic applications

Abstract: A nonlithographic technique that utilizes highly ordered anodized aluminum oxide (AAO) porous membrane as a template is employed as a general fabrication means for the formation of an array of vastly different two-dimensional lateral superlattice nanostructures The fact that material systems as different as metals, semiconductors, and carbon nanotubes can be treated with the same ease attest to the generality of this nanofabrication approach The original AAO membranes determine the uniformity, packing density, and size of the nanostructures The flexibility of using a variety of materials, the accurate control over fabrication process, and the command over AAO template attributes, gives us the freedom of engineering various physical properties determined by the shape, size, composition, and doping of the nanostructures The novel nanomaterial platform realized by this unique technique is powerfully enabling for a broad range of applications

Process for high yield fabrication of MEMS devices

Abstract: A MEMS fabrication process eliminates through-wafer etching, minimizes the thickness of silicon device layers and the required etch times, provides exceptionally precise layer to layer alignment, does not require a wet etch to release the moveable device structure, employs a supporting substrate having no device features on one side, and utilizes low-temperature metal-metal bonding which is relatively insensitive to environmental particulates. This process provided almost 100% yield of scanning micromirror devices exhibiting scanning over a 12° optical range and a mechanical angle of ± 3° at a high resonant frequency of 2.5 kHz with an operating voltage of only 20 VDC.