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  • 1
    Electronic Resource
    Electronic Resource
    Anisotropic properties of high-temperature polyimide thin films: Dielectric and thermal-expansion behaviors (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2014-2021 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multilayer poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide films of 172 μm total thickness (11.4 μm per layer) were prepared from the poly(amic acid) precursor solution through repetition of a spin-coat/softbake/cure process. Wide-angle x-ray diffraction results indicate that the polyimide molecules in the multilayer films are highly ordered along the chain axes as well as in the lateral direction and furthermore are highly oriented in the film plane as observed in a single-layer film of 11.4 μm thickness. The multilayer films showed the same dynamic mechanical properties and glass transition behavior (Tg = 330 °C) as a single-layer film. For the multilayer films both the in-plane dielectric constant (ε'XY) and out-of-plane thermal-expansion coefficient (αZ) were measured using time-domain spectroscopy and conventional thermal mechanical analysis, respectively. The ε'XY at room temperature was 3.69 (±0.08) over a frequency range of 0.35–2.50 THz. A similar ε'XY is predicted at frequencies of ≤0.35 THz. In contrast to the ε'XY, a relatively lower out-of-plane dielectric constant (ε'Z) was observed: ε'Z = 2.96–3.03 (±0.02) at 1 MHz, depending on moisture content in the film. The dielectric loss ε‘Z at 1 MHz was 0.011–0.014 (±0.001), depending on moisture content. The measured αZ was 74 ppm/°C over the temperature range of 25–150 °C, which was much higher than αXY = 2.6–5 ppm/°C. Consequently, large anisotropic ε' and α have been observed in the in plane and out of plane of the thermally imidized BPDA-PDA films. The anisotropic ε' and α were caused by high in-plane orientation of the polyimide molecules highly ordered along the chain axes in the films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351629
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  • 2
    Electronic Resource
    Electronic Resource
    Study of the Rayleigh acoustic mode in a-Si:H/a-SiNx:H superlattices (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 475-477 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Brillouin light-scattering technique has been exploited for studying the Rayleigh acoustic mode in superlattice films consisting of alternate layers of a-Si:H and a-SiNx:H. The phase velocity of the Rayleigh mode has been measured on superlattices with different thicknesses of the a-Si:H layer. The results obtained have been interpreted in terms of the effective medium model within the elastic continuum approximation; no anomalous behavior is observed, in contrast with previous ultrasonic measurements in superlattice with a minor nitrogen content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355823
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  • 3
    Electronic Resource
    Electronic Resource
    Drift mobility of semiconductive La0.5Sr0.5CoO3 films measured using the traveling wave method (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 580-582 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The conductivity and the drift mobility of La0.5Sr0.5CoO3 films deposited on fused silica substrates at 650 °C by pulsed-laser deposition have been measured by using the traveling-wave method. At room temperature, La0.5Sr0.5CoO3 films with semiconductivity have a hole density of 1×1021 cm−3, and drift mobility of 0.01 cm2/V s. The films underwent a paraferromagnetic transition around 240 K. The hopping process and tunneling effect of small polarons may be responsible for the conductive behavior above the Curie temperature. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125823
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  • 4
    Electronic Resource
    Electronic Resource
    Novel current–voltage characteristics in an InP-based resonant-tunneling high electron mobility transistor (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3608-3610 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report novel current–voltage characteristics in an InP-based resonant-tunneling high electron mobility transistor (RTHEMT). This device incorporates a pseudomorphic InGaAs/AlAs/InAs resonant-tunneling diode into the source of a nonalloyed ohmic contact InAlAs/InGaAs high electron mobility transistor. Both pronounced negative differential resistance and negative transconductance are observed at room temperature. Most significantly, a near-flat valley current is obtained in the output current–voltage characteristics. This feature is achieved by the nonalloyed ohmic contact cap layer structure employed in the HEMT, which significantly reduces the parasitic resistance. The novel characteristics of RTHEMTs should lead to many attractive circuit applications. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115333
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  • 5
    Electronic Resource
    Electronic Resource
    A new approach for synthesizing Ge quantum crystallites embedded in a-SiNx films (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1656-1658 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we present a new approach for synthesizing Ge quantum crystallites embedded in a-SiNx films. On the basis of preferential chemical bonding formation of Si-N and Ge-Ge, thin films with Ge clusters embedded in a-SiNx matrix have been prepared by the plasma enhanced chemical vapor deposition method with reactant gases of SiH4, GeH4 and NH3 mixed in hydrogen plasma at substrate temperature of 250 °C. Then the as-deposited films were annealed at 800 °C for 30 min in the vacuum for the crystallization of Ge clusters and the growth of nanometer-sized Ge quantum crystallites. These samples were characterized by infrared absorption spectra, transmission electron microscopy, x-ray diffraction, and Raman scattering spectra. The average size of Ge crystallites was found to be about 200 A(ring). By choosing conditions of the deposition and thermal-annealing treatment, the size of Ge quantum crystallites can be prepared in a controlled manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111821
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  • 6
    Electronic Resource
    Electronic Resource
    Preparation of Ge quantum crystallites embedded in a-SiN"x matrix by the PECVD method
    Amsterdam : Elsevier
    Solid State Communications 90 (1994), S. 549-551 
    Details
    ISSN: 0038-1098
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0038-1098(94)90118-X
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  • 7
    Electronic Resource
    Electronic Resource
    Joint action of ammonia and nitrite on Artemia nauplii
    Amsterdam : Elsevier
    Aquaculture 77 (1989), S. 329-336 
    Details
    ISSN: 0044-8486
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0044-8486(89)90217-2
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of UV exposure and thermal history on properties of a preimidized photosensitive polyimide (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 924-930 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The structure and properties of a preimidized photosensitive polyimide (Probimide PSPI, a copolyimide of benzophenonetetracarboxylic dianhydride with alkyl groups substituted aromatic diamines) were studied with variations of UV exposure energy and bake temperature by means of wide angle X-ray diffraction, dynamic mechanical thermal analysis, stress-strain analysis, and residual stress analysis. The X-ray diffraction patterns patterns indicate that the PSPI is amorphous in the solid state. The Tg was 378°C ∼ 410°C, depending upon the thermal history over the range of 350°C ∼ 400°C. At the glass transition region, the dynamic storage modulus E′ was very sensitive to both i-line exposure energy and thermal history. However, the mechanical stress-strain behavior at room temperature was primarily dependent on the thermal history. The mechanical properties were 2.6 GPa ∼ 2.9 GPa Young's modulus, 131 MPa ∼ 168 MPa tensile strength, 10% ∼ 12% yield strain, and 16% ∼ 74% elongation at break, depending upon the baking or annealing. These dynamic and static mechanical properties indicate that on the PSPI backbone, crosslinks are formed thermally as well as photochemically. The thermal crosslinks might be formed through thermal liberation of the labile alkyl groups of aromatic diamine moieties and subsequent coupling of the radicals. The thermal degradation was also evidenced in the mechanical properties degraded by baking above 375°C or annealing above 350°C. In addition, during baking and cooling, the residual stress was dynamically measured on Si wafers as a function of temperature. The stress at room temperature was 48 MPa ∼ 52 MPa for the PSPI films baked at 350°C or 400°C, regardless of i-line exposure.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321403
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  • 9
    Electronic Resource
    Electronic Resource
    Structure and properties of a photosensitive polyimide: Effect of photosensitive group (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 453-465 
    Details
    ISSN: 0887-6266
    Keywords: photosensitive polyimide ; thermal imidization ; in-plane orientation ; microvoid ; mechanical properties ; optical properties ; dielectric constant ; residual stress ; water diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photosensitive poly(p-phenylene biphenylteracarboximide) (BPDA-PDA) precursor was synthesized by attaching photocross-linkable 2-(dimethylamino)ethyl methacrylate (DMAEM) monomer to its poly(amic acid) through acid/base complexation. The polyimide thin films were prepared by a conventional cast/softbake/thermal imidization process from the photosensitive precursors with various concentrations of DMAEM. The structure and properties of the polyimide films were investigated by small-angle and wide-angle x-ray scattering, refractive indices and birefringence analysis, residual stress and relaxation analysis, stress-strain analysis, and dynamic mechanical thermal analysis. In comparison with the polyimide film from the poly(amic acid), the films, which were imidized from the photosensitive precursors, exhibited a better molecular order and microstructure; however, they exhibited less molecular orientation in the film plane. Despite the enhancement in both the molecular order and microstructure, the film properties (i.e., mechanical properties, thermal expansion, residual stress, optical properties, dielectric constant, and water sorption) degraded overall due to both the decrease in molecular in-plane orientation and the formation of microvoids caused by the bulky photosensitive group during thermal imidization. That is, on one hand, the PSPI precursor formation provides an advantageous, direct patternability to the BPDA-PDA precursor, and on the other hand, it results in degraded properties to the resulting polyimide film. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090330314
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  • 10
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    Defect formation and annealing behaviors of fluorine-implanted GaN layers revealed by positron annihilation spectroscopy (2009)
    American Institute of Physics
    Details
    Publication Date: 2009-02-09
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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