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  • 1
    Electronic Resource
    Electronic Resource
    Electronic structure of small GaAs clusters (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8015-8020 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of small GaxAsy clusters (x+y≤10) are calculated using the local density method. The calculation shows that even-numbered clusters tend to be singlets, as opposed to odd-numbered clusters which are open shell systems. This is in agreement with the experimental observations of even/odd alternations of the electron affinity and ionization potential. In the larger clusters, the atoms prefer an alternating bond arrangement; charge transfers are observed from Ga sites to As sites. This observation is also in agreement with recent chemisorption studies of ammonia on GaAs clusters. The close agreement between theoretical calculations and experimental results, together with the rich variation of electronic properties of GaAs clusters with composition makes GaAs clusters an ideal prototype system for the study of how electronic structure influences chemical reactivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460135
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  • 2
    Electronic Resource
    Electronic Resource
    Field-induced surface chemistry of NO (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6065-6069 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A microscopic theory of field adsorption is used to study the adsorption and reaction of NO on a Pt(111) surface in high electrostatic fields. We find that below 0.4 V/A(ring) only NO is adsorbed stably. Above this value dissociation sets in that leads around 1.2 V/A(ring) to the formation of N2O. A molecular orbital analysis is given of the reaction pathway and to identify the stabilization mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459494
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  • 3
    Electronic Resource
    Electronic Resource
    Raman scattering from PbTiO3 thin films prepared on silicon substrates by radio frequency sputtering and thermal treatment (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 394-399 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman scattering has been carried out on PbTiO3 thin films prepared on platinum-coated (100) silicon by radio-frequency (rf)-magnetron sputtering without substrate heating and a post-deposition thermal treatment. The Raman spectra obtained from the thin film are characteristic of powder Raman spectra: In comparison with the single crystal spectra, the intensity of the background is relatively high at low frequencies and the Raman lines are broad. The lattice phonon modes corresponding to the observed lines are identified by comparison with the data on single crystals and powder. The Raman frequencies for the thin film remarkably shift to low frequencies compared with single-crystal data. It is shown that the phenomenon of the frequency shifts is similar with the hydrostatic pressure effect on single crystals of PbTiO3. The result indicates that the thin films are composed of grains that are stressed depending on the grain size by neighboring grains of different orientations when they are split up into ferroelectric domains at the paraelectric-to-ferroelectric transition. This stress effect is significant even for a grain size of ∼0.5 μm. It is found that the lowest frequency E transverse optical (TO) mode in the thin film shows softening with increasing temperature as was reported in previous studies on single crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353862
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical investigation of minority carrier leakages of high-power 0.8 μm InGaAsP/InGaP/GaAs laser diodes (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2260-2262 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a theoretical model that accurately describes the effects of minority carrier leakage from the InGaAsP waveguide into InGaP cladding layers in high-power aluminum-free 0.8 μm InGaAsP/InGaP/GaAs separate confinement heterostructure lasers. Current leakage due to the relatively low band-gap discontinuity between the active region and the InGaP barrier can be eliminated by employing laser diodes with cavity length longer than 500 μm. Experimental results for lasers grown by low-pressure metalorganic chemical vapor deposition are in excellent agreement with the theoretical model. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112738
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  • 5
    Electronic Resource
    Electronic Resource
    Improvement of oxide quality by rapid thermal annealing in N2 (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3966-3969 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rapid thermal processing with a controlled cooling ramp as a postoxidation annealing in nitrogen is of considerable influence on the quality of thin (6 nm) thermal oxides. We studied how the annealing condition affected the electrical characteristics of the dielectrics, the charge-trapping properties, the gate voltage shift ΔVG, the flat band voltage shift ΔVFB, the increase of midgap interface state density ΔDitm under high field stress, the charge to breakdown, and the breakdown field. We found that controlled cooling after oxidation improved the interface between silicon and silicon dioxide. The postoxidation annealing in nitrogen reduced the fixed charge in oxides. The above measurements were correlated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354465
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  • 6
    Electronic Resource
    Electronic Resource
    Raman scattering study of lead zirconate titanate thin films prepared on silicon substrates by radio frequency magnetron sputtering (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6625-6631 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman scattering is used to characterize thin films of PbTi1−xZrxO3. The films have been prepared on platinum-coated (100) silicon by radio-frequency (rf)-magnetron sputtering without substrate heating followed by a post-deposition annealing at 600–650 °C. As the concentration of Zr is increased, the Raman peaks broaden and their intensities decrease more rapidly compared with bulk ceramic or powder samples, while the background intensity increases. The observations show that the crystal structure of the films is locally deformed and significantly disordered. With increasing x, the soft E(TO) mode shifts to lower frequencies. An additional Raman peak appears besides the phonon peaks expected in a perfect crystal. The soft mode strongly couples with the extra mode, similarly with the case of ceramic samples. The results are related to features of the thin films such as a frustrated phase transition, i.e., smaller differences between the lattice parameters a and c in comparison with powder data, and an electrical behavior showing a diffuse ferroelectric-to-paraelectric transition with a broad peak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355103
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  • 7
    Electronic Resource
    Electronic Resource
    Surface modification of YBa2Cu3Oy thin films with a scanning tunneling microscope (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2535-2537 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a systematic modification of thin YBa2Cu3Oy films with a scanning tunneling microscope. The samples include YBa2Cu3Oy films on MgO(001) and YBa2Cu3Oy/PrBa2Cu3Oy bilayer films on SrTiO3 (001). The bias voltage of the tip was kept negative and varied from −600 to −1200 mV. The tip was operated in a constant tunneling current mode with tunneling current 0.3–0.7 nA and scanning rate 1 Hz. Modification of the surface begins with nucleation of holes, or at the edge of a dislocation or protrusion on the surface, and is achieved by successively scanning a fixed area. We show the image obtained from an atomic force microscope which can help us look into the mechanism of the modification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357566
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  • 8
    Electronic Resource
    Electronic Resource
    Growth of high-Tc YBa2Cu3Oy films with an off-axis sputtering configuration (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 8419-8422 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using an off-axis rf sputtering configuration, we have prepared in situ high-Tc YBa2Cu3O7−y (YBCO) films with a relatively large deposition rate. The sputtering gas was a mixture of Ar and O2 (7:3) and the substrates were MgO(100) and SrTiO3(100). We found that the distance from the target to the substrate, d, is a key factor in the deposition rate. By decreasing d to a value of about 1.5–2.5 cm, we obtained a deposition rate as great as 2000–2500 A(ring) per hour with an rf power of 120 W and at a total pressure 100–200 mTorr. The transport behaviors of the as-grown YBCO films under magnetic fields are reported. The activation energy derived from the resistive transition in magnetic fields is thickness dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353411
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  • 9
    Electronic Resource
    Electronic Resource
    Microstructural and electrical properties of epitaxial PtSi/p-Si(100) co-deposited under ultrahigh vacuum (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6251-6255 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial PtSi/p-Si(100) contacts were fabricated by co-depositing Pt and Si on p-Si(100) at 450 °C in a dual electron gun chamber at a base pressure of 10−10 Torr. The PtSi/p-Si(100) film possessed six types of epitaxial modes, as indicated in the electron diffraction patterns. The average grain size of the PtSi grains was measured to be 100–300 A(ring) through the Moiré fringe image. The Schottky barrier height of the epitaxial PtSi/p-Si(100) diode was determined to be 0.249 eV at 100 K, with an ideality factor of 1.04. In contrast to this, the Schottky barrier height of the polycrystalline PtSi/p-Si(100) diode was 0.229 eV at 100 K, with an ideality factor of 1.05. The difference in Schottky barrier height was attributed to the difference in the atomic arrangement at interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355168
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  • 10
    Electronic Resource
    Electronic Resource
    In situ formation of Y-Ba-Cu-O epitaxial films by 40.68-MHz rf magnetron sputtering (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2731-2733 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The in situ epitaxial growth of the Y-Ba-Cu-O films on MgO (001) was carried out by 40.68- MHz rf magnetron sputtering with an on-axis single target. It appeared that the rf discharge strongly affected film composition, crystallinity, superconductivity, and reproducibility. Highly orientated superconducting films with the c-axis perpendicular to the substrate surfaces and having zero resistance transition temperature of 78.2 K were obtained without a post-annealing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348628
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