Showing papers on "Fabrication published in 2009"

Wafer-scale fabrication of separated carbon nanotube thin-film transistors for display applications.

Abstract: Preseparated, semiconductive enriched carbon nanotubes hold great potential for thin-film transistors and display applications due to their high mobility, high percentage of semiconductive nanotubes, and room-temperature processing compatibility. Here in this paper, we report our progress on wafer-scale processing of separated nanotube thin-film transistors (SN-TFTs) for display applications, including key technology components such as wafer-scale assembly of high-density, uniform separated nanotube networks, high-yield fabrication of devices with superior performance, and demonstration of organic light-emitting diode (OLED) switching controlled by a SN-TFT. On the basis of separated nanotubes with 95% semiconductive nanotubes, we have achieved solution-based assembly of separated nanotube thin films on complete 3 in. Si/SiO2 wafers, and further carried out wafer-scale fabrication to produce transistors with high yield (>98%), small sheet resistance (∼25 kΩ/sq), high current density (∼10 μA/μm), and super...

Materials Fabricated by Micro- and Nanoparticle Assembly ― The Challenging Path from Science to Engineering

Abstract: and strategies for the assembly of particle structures classified on the basis of their dimensionality. We survey the potential areas of application of the structures assembled from particles, and discuss why the technological potential of these structures is at present largely unrealized. Many of the challenges in the area of nanocolloidal assembly relate to the development of assembly processes that are scalable, controllable, rapid, and inexpensive. The power and versatility of colloidal-particle assemblies are best illustrated by the vast number of structures and strategies for their fabrication reported in the literature. A convenient way to classify the majority of the colloidal assemblies could be based on their dimensionality and degree of ordering ‐ three, two, one-dimensional, or independent clusters. In order to evaluate the ease and precision of the controlled fabrication of such materials, we also need to analyze in each case the physical principles by which a certain structure is assembled. The assembly can be accomplished by an extensive array of techniques based on numerous physical mechanisms. A survey of a few major groups of methods that have found use in the controlled assembly of particles into materials with well-organized and defined microstructures is presented in Table 1. The goal of these techniques is to collect the particles,

Very High Mobility in Solution-Processed Organic Thin-Film Transistors of Highly Ordered [1]Benzothieno[3,2-b]benzothiophene Derivatives

Abstract: Field-effect mobility as high as 5 cm2/(V s) is achieved in solution-processed organic thin-film transistors with the development of a method for growing highly-oriented crystalline films of [1]benzothieno[3,2-b]benzothiophene derivatives. A droplet of the solution is sustained at an edge of a structure on an inclined substrate, so that the crystalline domain grows in the direction of inclination. The oriented growth realizes excellent molecular ordering that manifests itself in micrometer-scale molecular terraces on the surface as a result of the self-organizing function of the material. The unprecedented performance achieved using an easy fabrication process has increased attractiveness of organic thin-film transistors for industrial applications.

3D metallic nanostructure fabrication by surfactant-assisted multiphoton-induced reduction.

Abstract: A laser direct-writing technique employing multiphoton absorption processes has become a powerful and widely used tool in the fabrication of micro-/nanometer-scale structures in the past decade because of its 3D fabrication ability. Using this technique, a number of 2D and 3D microstructures have been successfully created with polymers, glasses, and metals. In particular, since nanoscale metals exhibit unprecedented and unique properties such as electromagnetic field enhancement, catalysis, photoemission, and electronic conductivity never found in their bulk states, metal structures with nanoscale geometries have received much attention from various fields such as plasmonics, electronics, bioscience, and

Two- and three-dimensional folding of thin film single-crystalline silicon for photovoltaic power applications

Abstract: Fabrication of 3D electronic structures in the micrometer-to-millimeter range is extremely challenging due to the inherently 2D nature of most conventional wafer-based fabrication methods. Self-assembly, and the related method of self-folding of planar patterned membranes, provide a promising means to solve this problem. Here, we investigate self-assembly processes driven by wetting interactions to shape the contour of a functional, nonplanar photovoltaic (PV) device. A mechanics model based on the theory of thin plates is developed to identify the critical conditions for self-folding of different 2D geometrical shapes. This strategy is demonstrated for specifically designed millimeter-scale silicon objects, which are self-assembled into spherical, and other 3D shapes and integrated into fully functional light-trapping PV devices. The resulting 3D devices offer a promising way to efficiently harvest solar energy in thin cells using concentrator microarrays that function without active light tracking systems.

Three-dimensional microfabrication of materials by femtosecond lasers for photonics applications

Abstract: Femtosecond laser fabrication of three-dimensional structures for photonics applications is reviewed. Fabrication of photonic crystal structures by direct laser writing and holographic recording by multiple beam interference techniques are discussed. The physical mechanisms associated with structure formation and postfabrication are described. The advantages and limitations of various femtosecond laser microfabrication techniques for the preparation of photonic crystals and elements of microelectromechanical and micro-optofluidic systems are discussed.

Fabrication of large-area patterned photonic crystals by ink-jet printing

Abstract: Large-area patterned photonic crystals (PCs) with multi-stopbands were facilely fabricated by common ink-jet printers using polymer latex suspensions as inks.

InSb heterostructure nanowires: MOVPE growth under extreme lattice mismatch.

Abstract: We demonstrate the growth of InSb-based nanowire heterostructures by metalorganic vapour phase epitaxy and use it to integrate InSb on extremely lattice-mismatched III-V nanowire templates made of InAs, InP, and GaAs. Influence of temperature, V/III ratio, and diameter are investigated in order to investigate the growth rate and morphology. The range of growth temperatures used for InSb nanowire growth is very similar to that used for planar growth due to the nature of the precursor decomposition. This makes optimization of growth parameters very important, and more difficult than for most other nanowire III-V materials. Analysis of the InSb nanowire epitaxial quality when grown on InAs, InP, and GaAs, along with InSb segment and particle compositions are reported. This successful direct integration of InSb nanowires, on nanowire templates with unprecedented strain levels show great promise for fabrication of vertical InSb devices.

Suspended nanowires: Fabrication, design and characterization of fibers with nanoscale cores

Abstract: We report a new approach for the fabrication of nanowires: the direct drawing of optical fibers with air suspended nanoscale cores. The fibers were made from lead silicate glass using the extrusion technique for preform and jacket tube fabrication. Fibers with core diameters in the range of 420–720 nm and practical outer diameters of 110–200 μm were produced, the smallest core sizes produced to date within optical fibers without tapering. We explored the impact of the core size on the effective mode area and propagation loss of these suspended nanowires relative to circular nanowires reported to date. As for circular nanowires, the propagation loss of these suspended nanowires is dominated by surface roughness induced scattering.

Easy route to superhydrophobic copper-based wire-guided droplet microfluidic systems.

Abstract: Droplet-based microfluidic systems are an expansion of the lab on a chip concept toward flexible, reconfigurable setups based on the modification and analysis of individual droplets. Superhydrophobic surfaces are one suitable candidate for the realization of droplet-based microfluidic systems as the high mobility of aqueous liquids on such surfaces offers possibilities to use novel or more efficient approaches to droplet movement. Here, copper-based superhydrophobic surfaces were produced either by the etching of polycrystalline copper samples along the grain boundaries using etchants common in the microelectronics industry, by electrodeposition of copper films with subsequent nanowire decoration based on thermal oxidization, or by a combination of both. The surfaces could be easily hydrophobized with thiol-modified fluorocarbons, after which the produced surfaces showed a water contact angle as high as 171 degrees +/- 2 degrees . As copper was chosen as the base material, established patterning techniques adopted from printed circuit board fabrication could be used to fabricate macrostructures on the surfaces with the intention to confine the droplets and, thus, to reduce the system's sensitivity to tilting and vibrations. A simple droplet-based microfluidic chip with inlets, outlets, sample storage, and mixing areas was produced. Wire guidance, a relatively new actuation method applicable to aqueous liquids on superhydrophobic surfaces, was applied to move the droplets.

Deep reactive ion etching as a tool for nanostructure fabrication

Abstract: Deep reactive ion etching (DRIE) is investigated as a tool for the realization of nanostructures and architectures, including nanopillars,siliconnanowires or carbon nanotubes on Si nanopillars, nanowalls, and nanonetworks The potential of combining top-down fabrication methods with the bottom-up synthesis of one-dimensional nanocomponents is assessed The field-emission properties of carbon nanotubes/Si pillars hybrid structures are measured, as well as the transport properties of large-area nanowires obtained via nanowire lithography The potential of DRIE for the fabrication of three-dimensional nanostructures is also revealed

Photovoltaics Based on Hybridization of Effective Dye‐Sensitized Titanium Oxide and Hole‐Conductive Polymer P3HT

Abstract: Here, the fabrication of quasi-solid-state TiO 2 /dye/poly(3-hexylthiophene) (P3HT) solar cells is reported, in which the dyes with oleophilic thienyl groups were employed and ionic liquid (IL), 1-ethyl-3-methylimidazolium (EMIm) containing lithium bis(trifluromethanesulfone)amide (Li-TFSI) and 4-tertbutylpyridine (t-BP) are assembled with dyed TiO 2 surfaces. One of the devices gave a high conversion efficiency of up to 2.70% under 1 sun illumination. The excellent performance is ascribed to successful molecular self-organization at interface of the dye molecules and P3HT, and to the efficient charge separation and diffusion acquired by introduction of the IL coupled with Li-TFSI and t-BP.

A full description of a simple and scalable fabrication process for electrowetting displays

Abstract: Electrowetting displays provide a high white state reflectance of >50% and have attracted substantial world-wide interest, yet are primarily an industrially led effort with few details on preferred materials and fabrication processes. Reported herein is the first complete description of the electrowetting display fabrication process. The description includes materials selection, purification and all fabrication steps from substrate selection to sealing. Challenging materials and fabrication processes include dielectric optimization, fluoropolymer selection, hydrophilic grid patterning, liquid dosing, dye purification and liquid ionic content. The process described herein has produced pixel arrays that were switched at <15 V on active-matrix backplanes, and which have individual sub-pixel areas of <50 × 150 µm2. The majority of fabrication processes can conform to liquid-crystal style manufacturing equipment, and therefore can be readily adopted by many display practitioners. Also presented are additional tips and techniques, such as controlling the onset of oil film break-up in an electrowetting display. This paper should enable anyone skilled in displays or microfabrication to quickly and successfully set up research and fabrication of electrowetting displays.

Dense and near-net-shape fabrication of Si3N4 ceramics

Abstract: With silicon nitride significant progress has been made in order to search for fully dense, strong, reliable structural ceramics to find wide use in applications at high temperatures which are allowing new and innovative solutions to component design problems. Taking into account that more and more ceramic components based on Si3N4 are being used in the aerospace and automobile industries, it is a great challenge to fabricate such complex-shaped components with high reliability and with defect-free microstructures such as pores, inclusions or any other inhomogeneity at acceptable costs. On the other side, the high hardness of Si3N4 ceramics is almost always cost prohibitive to shape components by hard machining. It is therefore great effort exhibited in the development of near-net-shape fabrication processes that can produce complex-shaped components with a minimum of machining as well as to minimize the number and size of microstructural defects within design limits. In this review, the fabrication of near-net-shape Si3N4 ceramics is given in detail. All kinds of these techniques (injection molding, gelcasting, robocasting, mold shape deposition, rapid prototyping) and their advantages and disadvantages are explained.

Ink-jet printing of ceramic micro-pillar arrays

Abstract: This review illustrates the fabrication of different kinds of micro-pillar array structures by ink-jet printing process So the fabrication of 1–3 piezoelectric composites and photocatalytic devices by deposition, respectively of PZT and TiO2 suspensions will be mainly reported First, different investigations were carried out to adjust the ceramic suspensions to be compatible with ink-jet printing process Afterwards, this study reveals how the main characteristics of the micro-pillar array structures (morphology, definition, compacity, etc) strongly depend on the conditions of fabrication (configuration of the deposit, driving parameters of the printing head, delay between two successive layers, etc) and on the formulation of the ceramic suspensions (ceramic loading, nature and content of binder and surfactant, etc) Finally, sintered PZT and TiO2 micro-pillar structures were achieved with a very good definition (around 40 μm) The study of the functional properties of the corresponding structures is in progress

A low-cost, high-yield fabrication method for producing optimized biomimetic dry adhesives

Abstract: We present a low-cost, large-scale method of fabricating biomimetic dry adhesives. This process is useful because it uses all photosensitive polymers with minimum fabrication costs or complexity to produce molds for silicone-based dry adhesives. A thick-film lift-off process is used to define molds using AZ 9260 photoresist, with a slow acting, deep UV sensitive material, PMGI, used as both an adhesion promoter for the AZ 9260 photoresist and as an undercutting material to produce mushroom-shaped fibers. The benefits to this process are ease of fabrication, wide range of potential layer thicknesses, no special surface treatment requirements to demold silicone adhesives and easy stripping of the full mold if process failure does occur. Sylgard® 184 silicone is used to cast full sheets of biomimetic dry adhesives off 4" diameter wafers, and different fiber geometries are tested for normal adhesion properties. Additionally, failure modes of the adhesive during fabrication are noted and strategies for avoiding these failures are discussed. We use this fabrication method to produce different fiber geometries with varying cap diameters and test them for normal adhesion strengths. The results indicate that the cap diameters relative to post diameters for mushroom-shaped fibers dominate the adhesion properties.

Wafer-level fabrication of GaN-based vertical light-emitting diodes using a multi-functional bonding material system

Abstract: We first report on the fabrication of 2 inch wafer-level GaN-based vertical light-emitting diodes (LEDs) by using a multi-functional bonding material system, which is composed of a thick Cu diffusion barrier and a bonding layer. The bonding material system superbly absorbs laser-induced stress and also effectively serves as a barrier to the indiffusion of Sn to the active region. Fully packaged vertical LEDs fabricated with indium tin oxide (ITO)/AgCu contact and the bonding material system give an operating voltage of 3.35 V at 350 mA. After over 1800 h, the operating voltages remain stable, and the reverse currents are in the range 3–8 × 10−7 A at −5 V.

Plasmonic components fabrication via nanoimprint

Abstract: A review report on nanoimprinted plasmonic components is given. The fabrication of different metal–dielectric geometries and nanostructured surfaces that support either propagating or localized surface plasmon modes is discussed. The main characteristics and advantages of the nanoimprint technology for the fabrication of various plasmonic structures are outlined. The discussion of plasmonic waveguiding structures focuses on planar waveguides based on metal strips embedded into a dielectric and on profiled metal surfaces. Nanoimprint-based fabrication of two-dimensional nanostructured plasmonic surfaces for enhanced transmission studies and sensor applications is also discussed. Throughout the report, the main fabrication schemes are described, as well as the challenges facing future manufacturing of plasmonic components for device applications.

Novel Top-Down Wafer-Scale Fabrication of Single Crystal Silicon Nanowires

Abstract: A now low-cost, top-down nanowire fabrication technology Is presented not requiring nanolithography and suitable for any conventional microtechnology cleanroom facility. This novel wafer-scale process technology uses a combination of angled thin-film deposition and etching of a metal layer In a precisely defined cavity with a single micrometer-scale photolithography step. Electrically functional silicon and metallic nanowires with lengths up to several millimeters, lateral widths of similar to 100 nm, and thicknesses similar to 20 nm have been realized and tested. Device characterization Includes a general description of device operation, electrochemical biasing, and sensitivity for sensor applications followed by electrical measurements showing linear I-v characteristics with specific contact resistivity rho(c) similar to 4 x 10(-4) Omega cm(2) and electrochemical behavior of the oxidized silicon nanowires Is described with the site-binding model

Ultra-fast fabrication of colloidal photonic crystals by spray coating.

Abstract: An ultra-fast fabrication of large-scale colloidal PCs via spray coating was demonstrated. The latex spheres with hydrophobic core and hydrophilic shell were designed, and the latex shell with abundant COOH groups resulted in strong hydrogen bonding interaction among latex spheres, which boosted latex arrangement during the spray procedure. The resultant samples with area of 7 x 12 cm 2 were easily fabricated within 1 min on different substrates. This ultra-fast fabrication procedure would be of great importance for the practical application of PCs for optic devices and functional coatings.

Fabrication of Molded Interconnection Devices by Ultrasonic Hot Embossing on Thin Polymer Films

Abstract: Ultrasonic hot embossing allows fabrication of metal patterns onto a polymer film with a low cost and rapid process. A polymer layer with a thin metal film on top is welded onto the polymer substrate where there are protruding micro structures on the tool. Edges around the protruding structures cut the metal layer and ensure electrical insulation. The entire process performs in a few seconds. The non-welded areas are mechanically removed after this process. An antenna of a radio frequency identification device (RFID) and a flexible membrane keyboard were fabricated by embossing 10- mum-thick conductive paths from an aluminum foil onto polypropylene films, 150 and 250 mum in thickness. Antenna circuits have been proven to show the expected resonance frequencies and the keyboard was successfully employed as an input device for a PC.

Semiconductor package with embedded die and its methods of fabrication

Abstract: Embodiments of the present invention describe a semiconductor package having an embedded die. The semiconductor package comprises a coreless substrate that contains the embedded die. The semiconductor package provides die stacking or package stacking capabilities. Furthermore, embodiments of the present invention describe a method of fabricating the semiconductor package that minimizes assembly costs.

Nanostructured superhydrophobic, superoleophobic and/or superomniphobic coatings, methods for fabrication, and applications thereof

Abstract: Systems, techniques and applications for nanoscale coating structures and materials that are superhydrophobic with a water contact angle greater than about 140° or 160° and/or superoleophobic with an oil contact angle greater than about 140° or 160°. The nanostructured coatings can include Si or metallic, ceramic or polymeric nanowires that may have a re-entrant or mushroom-like tip geometry. The nanowired coatings can be used in various self-cleaning applications ranging from glass windows for high-rise buildings and non-wash automobiles to pipeline inner surface coatings and surface coatings for biomedical implants.

Fabricating capacitive micromachined ultrasonic transducers with a novel silicon-nitride-Based wafer bonding process

Abstract: We report the fabrication and experimental testing of 1-D 23-element capacitive micromachined ultrasonic transducer (CMUT) arrays that have been fabricated using a novel wafer-bonding process whereby the membrane and the insulation layer are both silicon nitride. The membrane and cell cavities are deposited and patterned on separate wafers and fusion-bonded in a vacuum environment to create CMUT cells. A user-grown silicon-nitride membrane layer avoids the need for expensive silicon-on-insulator (SOI) wafers, reduces parasitic capacitance, and reduces dielectric charging. It allows more freedom in selecting the membrane thickness while also providing the benefits of wafer-bonding fabrication such as excellent fill factor, ease of vacuum sealing, and a simplified fabrication process when compared with the more standard sacrificial release process. The devices fabricated have a cell diameter of 22 mum, a membrane thickness of 400 nm, a gap depth of 150 nm, and an insulation thickness of 250 nm. The resonant frequency of the CMUT in air is 17 MHz and has an attenuation compensated center frequency of ~9 MHz in immersion with a -6 dB fractional bandwidth of 123%. This paper presents the fabrication process and some characterization results.

Patterned electrode vertical field effect transistor fabricated using block copolymer nanotemplates

Abstract: We report the design and implementation of a vertical organic field effect transistor which is compatible with standard device fabrication technology and is well described by a self consistent device model. The active semiconductor is a film of C60 molecules, and the device operation is based on the architecture of the nanopatterned source electrode. The relatively high resolution fabrication process and maintaining the low-cost and simplicity associated with organic electronics, necessitates unconventional fabrication techniques such as soft lithography. Block copolymer self-assembled nanotemplates enable the production of conductive, gridlike metal electrode. The devices reported here exhibit On/Off ratio of 104.

Terahertz vacuum electronic circuits fabricated by UV lithographic molding and deep reactive ion etching

Abstract: The 0.22 THz vacuum electronic circuits fabricated by UV lithography molding and deep reactive ion etching processes are under investigation for submillimeter wave applications. Eigenmode transient simulations show that, accounting for realistic values of our currently achievable fabrication tolerances, the transmission, and dispersion properties of the operation modes of a TE-mode, staggered, double grating circuit are maintained within less than 1 dB and 2% deviation, respectively. Scanning electron microscopy and atomic force microscopy analyses of the fabricated circuit samples demonstrate that both of the microelectromechanical system fabrication approaches produce circuits with ±3–5 μm dimensional tolerance and ∼30 nm surface roughness.

Chemically-induced Mobility Gaps in Graphene Nanoribbons: A Route for Upscaling Device Performances

Abstract: We report a first-principles based study of mesoscopic quantum transport in chemically doped graphene nanoribbons with a width up to 10 nm. The occurrence of quasibound states related to boron impurities results in mobility gaps as large as 1 eV, driven by strong electron-hole asymmetrical backscattering phenomena. This phenomenon opens new ways to overcome current limitations of graphene-based devices through the fabrication of chemically-doped graphene nanoribbons with sizes within the reach of conventional lithography.