Showing papers by "Paul H. Holloway published in 2002"

Fabrication and testing of a magnetically actuated micropump

Abstract: A micropump has been fabricated in a modular fashion using silicone elastomers, which are cheap, tough, durable and inert. For modular assembly, molded bodies capture a thin valve membrane, and a diaphragm is glued on top. After attaching a novel, magnetically oriented permanent magnet composite membrane, as well as inlet and outlet tubes, the pump is activated by an electromagnet. Under a differential water head, the valve opened at ∼600 Pa. A pump 15 mm in diameter, 20 mm long, weighing 10 g, had a maximum pump rate for air of 260 μl/min at 1.9 W.

High-Power GaN Electronic Devices

Abstract: Gallium Nitride (GaN) and related materials (especially AlGaN) recently have attracted a lot of interest for applications in high-power electronics capable of operation at elevated temperatures and high frequencies. The AlGaInN system offers numerous advantages. These include wide bandgaps, good transport properties, the availability of heterostructures (particularly AlGaN/GaN), the experience base gained by the commercialization of GaN-based laser and light-emitting diodes and the existence of a high growth rate epitaxial method (hydride vapor phase epitaxy, HVPE) for producing very thick layers or even quasisubstrates. These attributes have led to rapid progress in the realization of a broad range of GaN electronic devices. AlxGa1-xN (x=0 ∼.25) Schottky rectifiers were fabricated in a lateral geometry employing p+-implanted guard rings and rectifying contact overlap onto an SiO2 passivation layer. The reverse breakdown voltage (VB) increased with the spacing between Schottky and ohmic metal contacts, re...

Control of point defects and space charge in electroluminescent ZnS:Mn thin films

Abstract: The mechanisms leading to improved brightness, efficiency, and stability of alternating-current thin-film electroluminescent (ACTFEL) ZnS:Mn phosphors have been studied. Previously we have shown that ex situ codoping of the sputter deposited ZnS:Mn active layer with K and Cl results in a 53% improvement in brightness, a 62% improvement in efficiency, and better 100 h accelerated aging stability. In this work, we demonstrate that these improvements result from a 75% increase in excitation efficiency for conduction electrons, combined with a small decrease in both light outcoupling and nonradiative recombination. Electrical properties data were used to determine that there is a reduced amount of static space charge in the codoped films, resulting in a larger average field, increased excitation efficiency, and increased charge multiplication. The reduced space charge is attributed to the addition of charge compensating zinc vacancy–chlorine complexes and isolated chlorine point defects, which are acceptor an...

Reduced voltage artificial eyelid for protection of optical sensors

Abstract: The fabrication, testing and performance of a new device for the protection of optical sensors will be described. The device consists of a transparent substrate, a transparent conducting electrode, insulating polymers, and a reflective top electrode layer. Using standard fabrication techniques, arrays of apertures can be created with sizes ranging from micrometers to millimeters. A stress gradient resulting from different coefficients of thermal expansion between the top polymer layer and the reflective metal electrode, rolls back the composite thin film structure from the aperture area following the chemical removal of a release layer, thus forming the open condition. The application of a voltage between the transparent conducting and reflective metal electrodes creates an electrostatic force that unrolls the curled film, closing the artificial eyelid. Fabricated devices have been completed on glass substrates with indium tin oxide electrodes. The curled films have diameters of less than 100micrometers with the arrays having fill factor transparencies of over 70%. Greater transparencies are possible with optimized designs. The electrical and optical results from the testing of the artificial eyelid will be discussed.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Microstructural characterization of radio frequency magnetron sputter-deposited Ga2O3:Mn phosphor thin films

Abstract: Ga2O3:Mn phosphor thin films have been prepared by radio frequency (rf) magnetron sputtering of a 2 mol % Mn-doped Ga2O3 target in an oxygen–argon mixture atmosphere. The deposition rate of the films decreased from 14 to 12 A/min when the working gas pressure decreased from 30 to 2 mTorr, while the O/Ga ratio of ∼1.5 did not systematically depend on the pressure. Films deposited at higher working gas pressure had a porous columnar structure containing a large void, typical of zone 1 growth, while films produced at lower pressure had relatively smooth surfaces with a dense structure, typical of zone T growth. The results obtained are consistent with energetic particle bombardment of the depositing films promoting surface adatom mobility at lower working gas pressure. Films deposited at working gas pressures⩾15 mTorr showed a random orientation after a postdeposition anneal at 1000 °C. Below 15 mTorr, annealed films were strongly textured with the (111) and (020) planes parallel to the surface.

Effects of a Ni cap layer on transparent Ni/Au ohmic contacts to p-GaN

Abstract: Ohmic contacts to p-GaN were obtained after annealing Ni/Au and Ni/Au/Ni contacts in flowing O2. Both Ni-capped p-GaN/Ni/Au and uncapped Ni/Au contacts were shown to result in specific contact resistance of ∼10−4 Ω cm2. In both cases, transparent NiO and thin, porous Au films were formed. Ni/Au contacts exhibited optical transmittance at λ=450 nm of >85%. Addition of the Ni cap layer was shown to increase the thermal stability of thin Ni/Au ohmic contacts and increase the 450 nm transmittance to 93%, while maintaining a low contact resistance. The ability of the capping layer to produce these improvements was discussed based on a total energy model of thin film morphology.

High speed, large motion electrostatic artificial eyelid

Abstract: The fabrication, testing and performance of a new device for the protection of optical sensors are described. The device consists of a transparent substrate, a transparent conducting electrode, insulating polymers, and a reflective top electrode layer. Using standard fabrication techniques, arrays of apertures can be created with sizes ranging from micrometers to millimeters. A stress gradient resulting from different thermal coefficients of expansion between the top polymer layer and the reflective metal electrode, rolls back the composite thin film structure from the aperture area following the chemical removal of a release layer. The application of a voltage between the transparent conducting and reflective metal electrodes creates an electrostatic force that unrolls the curled film, closing the artificial eyelid. Fabricated devices have been completed on glass substrates with indium tin oxide electrodes. The curled films have diameters of less than 100 /spl mu/m with the arrays having fill factor transparencies of over 80%.

Method and device for producing near-infrared radiation

Abstract: The subject invention pertains to a method, apparatus, and composition of matter for producing near-infrared (near-IR) radiation. The subject invention can incorporate a polymer and a metal-containing compound, wherein the metal-containing compound can incorporate a metal-ligand complex, wherein when the metal-ligand complex becomes excited, energy is transferred from the ligand to the metal, wherein, the energy transferred to the metal by sensitization is emitted as near-infrared radiation. In a specific embodiment, the subject invention relates to a composition of matter having a luminescent polymer and a metal containing compound where the metal containing compound incorporates a metal-Iigand complex such that the absorption spectrum of the metal-ligand complex at least partially overlaps with the emission spectrum of the luminescent polymer. As the absorption spectrum of the metal-ligand complex at least partially overlaps with the emission spectrum of the luminescent polymer, when the luminescent polymer becomes electronically excited energy can be transferred from the luminescent polymer to the metal-ligand complex. At least a portion of the energy transferred from the luminescent polymer to the metal-ligand complex can then be emitted by the metal-ligand complex as near-infrared radiation. The subject invention can incorporate polymers which are conjugated or non-conjugated and luminescent or non-luminescent. In a specific embodiment, conjugated polymers which are luminescent can be utilized.

Method and apparatus for producing near-infrared radiation

Abstract: The subject invention pertains to a method, apparatus, and composition of matter for producing near-infrared (near-IR) radiation. The subject invention can incorporate a polymer and a metal-containing compound, wherein the metal-containing compound can incorporate a metal-ligand complex, wherein when the metal-ligand complex becomes excited, energy is transferred from the ligand to the metal, wherein, the energy transferred to the metal by sensitization is emitted as near-infrared radiation. In a specific embodiment, the subject invention relates to a composition of matter having a luminescent polymer and a metal containing compound where the metal containing compound incorporates a metal-ligand complex such that the absorption spectrum of the metal-ligand complex at least partially overlaps with the emission spectrum of the luminescent polymer. As the absorption spectrum of the metal-ligand complex at least partially overlaps with the emission spectrum of the luminescent polymer, when the luminescent polymer becomes electronically excited energy can be transferred from the luminescent polymer to the metal-ligand complex. At least a portion of the energy transferred from the luminescent polymer to the metal-ligand complex can then be emitted by the metal-ligand complex as near-infrared radiation. The subject invention can incorporate polymers which are conjugated or non-conjugated and luminescent or non-luminescent. In a specific embodiment, conjugated polymers which are luminescent can be utilized.

Procede et appareil pour generer un rayonnement infrarouge proche

Abstract: L'invention concerne un appareil, un procede et une composition pour generer un rayonnement infrarouge proche. L'objet de l'invention peut comprendre un polymere et un compose contenant un metal, ledit compose contenant un metal pouvant comprendre un complexe metal-ligand. Lorsque ce complexe metal-ligand est excite, de l'energie est transferee depuis le ligand vers le metal, l'energie transferee vers le metal par sensibilisation etant emise comme du rayonnement infrarouge proche. Dans un mode de realisation determine, l'invention concerne une composition comprenant un polymere luminescent et un compose contenant un metal, ledit compose contenant un metal integrant un complexe metal-ligand de facon que le spectre d'absorption du complexe metal-ligand recouvre au moins partiellement le spectre d'emission du polymere luminescent. Dans la mesure ou le spectre d'absorption du complexe metal-ligand recouvre au moins partiellement le spectre d'emission du polymere luminescent, quand le polymere luminescent est excite electroniquement, de l'energie peut etre transferee du polymere luminescent vers le complexe metal-ligand. Au moins une partie de l'energie transferee du polymere luminescent vers le complexe metal-ligand peut ensuite etre emise par le complexe metal-ligand sous forme de rayonnement infrarouge proche. L'invention peut couvrir des polymeres conjugues ou non conjugues et luminescents ou non luminescents. Dans un mode de realisation determine, on peut utiliser des polymeres conjugues qui ne sont pas luminescents.