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  • 1
    Electronic Resource
    Electronic Resource
    Microstructural studies of epitaxial Ge films grown on [100] GaAs by laser photochemical vapor deposition (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3883-3895 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ge films grown on [100] GaAs by laser photochemical vapor deposition (LPVD) in parallel geometry at temperatures (Ts) ranging from ∼240 to 415 °C have been examined by transmission electron microscopy. For 285 ≤Ts(approximately-less-than)330 °C, a thin (250–700 A(ring)) epitaxial film is grown initially but a switch to amorphous material is subsequently observed. At higher substrate temperatures (Ts (approximately-greater-than)400 °C), thicker ((approximately-greater-than)800 A(ring)) epitaxial Ge films are grown before the transition to polycrystalline material takes place. In the absence of external 193-nm laser radiation (i.e., growing by conventional low-pressure chemical vapor deposition), the Ge films are completely amorphous (285 ≤Ts≤330 °C) or heavily defected polycrystalline (Ts∼400 °C). The 〉100 °C temperature reduction for the growth of epi Ge films made possible by LPVD is attributed to the direct production of a species (GeH3) by the laser which is collisionally converted to Ge2H6 en route to the substrate. Upon reaching the [100] GaAs surface, the digermane is pyrolyzed. Experiments with [100] substrates tilted 3° toward [110] yielded thinner (∼120 A(ring)), but smooth, epitaxial films which is attributed to the higher density of available nucleation sites. Films grown at 280–330 °C on [111] oriented GaAs were completely amorphous which appears to arise from reduced adatom mobilities on [111] surfaces. These results clearly demonstrate the feasibility of photochemically generating a species which migrates to the surface and alters the chemistry at a substrate (which is itself not illuminated by the optical source) so as to permit the growth of epitaxial semiconductor films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343352
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  • 2
    Electronic Resource
    Electronic Resource
    NH3 as a photosensitizer in the epitaxial growth of Ge on GaAs by laser photochemical vapor deposition (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 65-67 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The viability of ammonia as a sensitizer for the growth of epitaxial Ge on GaAs (100) by laser photochemical vapor deposition (LPVD) has been investigated. Specifically, NH3/GeH4/He (0.8/55.0/95 sccm, 5.5 Torr total pressure) mixtures have been irradiated by an excimer laser beam (ArF, 193 nm) in parallel geometry and for substrate temperatures (Ts) in the range 25≤Ts〈400 °C. As evidenced by a more than an order of magnitude acceleration in the Ge film growth rate (factor of ∼33 improvement at 305 °C), even trace amounts of NH3 added to the gas stream efficiently couple the laser radiation to the Ge precursor (GeH4) without incorporating significant concentrations of N and H into the film. Auger, secondary-ion mass spectrometry (SIMS), and x-ray photoelectron spectroscopy analyses of the films show the nitrogen content to be negligible (〈1%). Also, the slight amount of hydrogen detected by SIMS appears to arise from hydrocarbon contaminants rather than from the ammonia. Transmission electron microscopy studies demonstrate that films grown at Ts≥300 °C are epitaxial with an amorphous overlayer. Embedded within the amorphous matrix are Ge microcrystals which are textured, having their 〈112〉 axes parallel to the substrate normal. The beneficial effect of NH3 on the growth rate of LPVD Ge films is attributed to the photolytic production of hydrogen atoms which efficiently decompose GeH4 by hydrogen abstraction collisions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101755
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  • 3
    Electronic Resource
    Electronic Resource
    Low-resistance nonalloyed ohmic contacts on p-type GaAs using GaSb/GaAs strained-layer superlattices (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 570-571 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Employing a GaSb/GaAs strained-layer superlattice and a GaSb cap, specific contact resistivities as low as 3.2×10−7 Ω cm2 have been realized for nonalloyed ohmic contact to p-type GaAs. This contact structure is shown to give low contact resistances irrespective of the contact metals, including AuBe, AuGe/Ni/Au, and Au. Excellent thermal stability for AuBe contacts was obtained when sintered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101835
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  • 4
    Electronic Resource
    Electronic Resource
    Epitaxial growth of Ge films on GaAs (285–415 °C) by laser photochemical vapor deposition (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1710-1712 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial Ge films have been grown on [001]GaAs by laser photochemical vapor deposition (LPVD) for substrate temperatures (Ts) in the 285≤Ts≤415 °C interval. Films 400–700 A(ring) thick were grown at rates up to ∼1 A(ring) s−1 (0.6–5 nm/min) by photodissociating GeH4 with an ArF (193 nm) laser in parallel geometry (i.e., laser beam passes above and parallel to substrate). The quality of the Ge/GaAs heterointerfaces has been examined by plan-view and cross-sectional transmission electron microscopy. Convergent beam electron diffraction, selected area diffraction patterns, and lattice images show the LPVD films to be epitaxial, whereas films grown in the absence of ultraviolet laser radiation (i.e., by conventional chemical vapor deposition) are amorphous (Ts=305 °C) or heavily defected polycrystalline (Ts=415 °C). Epitaxy apparently hinges on the laser production of a species which migrates more than 10–60 mean free paths to reach the substrate (or is collisionally transformed en route into a more stable species) and dramatically alters the surface chemistry. The large number of collisions involved points to the transformation of photochemically generated GeH2 or GeH3 into Ge2H6 as the key gas phase reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99025
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  • 5
    Electronic Resource
    Electronic Resource
    Growth of high quality gallium arsenide on HF-etched silicon (001) by chemical beam epitaxy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1653-1655 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: HF etching followed by relatively low temperature (≈600 °C) pretreatment is shown to provide a suitable substrate for the heteroepitaxial growth of GaAs on Si(100) by CBE using TEGa and AsH3 as sources. Rutherford backscattering (RBS), photoluminescence (PL), transmission electron microscopy (TEM), and Raman measurements show the low-defect nature of the GaAs epilayer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108616
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  • 6
    Electronic Resource
    Electronic Resource
    High resolution transmission electron microscopy study of a GaAs/Si heterostructure grown by chemical beam epitaxy (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 616-618 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have successfully grown epitaxial GaAs on a Si(001) substrate by chemical beam epitaxy (CBE). Misfit dislocations and stacking faults in the GaAs/Si interface have been analyzed by high resolution transmission electron microscopy (HRTEM). The results indicate that the lattice mismatch between GaAs epilayer and Si substrate is completely accommodated mostly by 90° pure-edge misfit dislocations, and partly by 60° mixed misfit dislocations and stacking faults. Residual amorphous patches, presumably of SiO2, on the substrate surface appear to act as nucleation sites for stacking faults. Areas of thin amorphous layer on the substrate do not seem to prevent the epitaxial growth of GaAs on the Si substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106571
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  • 7
    Electronic Resource
    Electronic Resource
    Spontaneous ordering of bimodal ensembles of nanoscopic gold clusters (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 396 (1998), S. 444-446 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The controlled fabrication of very small structures at scales beyond the current limits of lithographic techniques is a technological goal of great practical and fundamental interest. Important progress has been made over the past few years in the preparation of ordered ensembles of metal and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/24808
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  • 8
    Electronic Resource
    Electronic Resource
    Hard elastic carbon thin films from linking of carbon nanoparticles (1996)
    [s.l.] : Nature Publishing Group
    Nature 383 (1996), S. 321-323 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Based on the high pressure arc plasma methods developed to produce fullerene molecules and nanotubes, we have used a high local gas pressure carbon arc technique for thin film deposition7. The carbon source is an arc on a graphite cathode within a high-pressure region created by a nitrogen or ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/383321a0
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  • 9
    Electronic Resource
    Electronic Resource
    An investigation of misfit dislocations in Al on (001) GaAs grown by chemical beam epitaxy (1993)
    Springer
    Interface science 1 (1993), S. 99-113 
    Details
    ISSN: 1573-2746
    Keywords: Metallization ; high-resolution electron microscopy ; aluminium on GaAs ; misfit dislocations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We report a transmission electron microscope study of the morphology and interfacial structure of Aluminium grown on (001) GaAs by chemical beam epitaxy (CBE). The Al grows in islands for all thicknesses deposited, and exhibits four distinct orientation relationships with respect to the substrate. One of these orientation relationships becomes dominant as growth progresses, with (011)Al parallel to (001)GaAs. Misfit dislocations can be seen in the interface between this orientation and the substrate with Burgers vector 1/4(110)GaAs, and a crystallographic analysis shows that these dislocations are associated with interfacial steps of height 1/2[001]GaAs. In (001)Al on (001)GaAs, the existence of these dislocations has in the past been regarded as evidence for the existence of a rigid-body shift of the Al in the interfacial plane. Using cross-sectional high-resolution TEM, it is shown that this shift is not present in the (011) orientation. The similarity in the microstructure and crystallography of the (001) and (011) orientations leads us to suggest that there is also no shift in (001) Al on (001)GaAs. This is in conflict with previous investigations of this system using a wide variety of techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203599
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  • 10
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    Low‐resistance nonalloyed ohmic contacts onp‐type GaAs using GaSb/GaAs strained‐layer superlattices (1989)
    American Institute of Physics
    Details
    Publication Date: 1989-08-07
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics
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