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  • 1
    Electronic Resource
    Electronic Resource
    Regrowth of a GaAs layer for n-GaAs ohmic contacts (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4385-4389 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reaction of Au with GaAs in conventional NiAuGe/GaAs ohmic contacts results in rough interfaces, poor surface morphology, and deterioration at the edges of films. To improve these properties, ohmic contacts to GaAs were formed by heating initially discrete layers of volatile arsenic and nonvolatile gallium under a Ge–Au alloy thin film. The layer sequence beginning at the air interface was AuGe(1500 A(ring))/As(500 A(ring))/Ga(400 A(ring)), all evaporated onto chemically cleaned (100) GaAs surfaces, followed by annealing at 400 to 650 °C in forming gas. A regrown layer of highly doped GaAs was formed between the AuGe layer and the original GaAs substrate. This layer was characterized by scanning Auger electron spectroscopy, scanning electron microscopy, and electrical measurements. The carrier concentration of the regrown GaAs layer was estimated from four-point probe data to be in the range of 1019 to 1020 cm−3. The specific contact resistivity for the AuGe/As/Ga/GaAs regrown at 550 °C for 10 min was ≈1.5×10−5 Ω cm2, which is similar to values measured for AuGe/GaAs annealed at 450 °C for 2 min. The mechanism of GaAs regrowth and ohmic contact formation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350776
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  • 2
    Electronic Resource
    Electronic Resource
    Surface passivation of GaAs with P2S5-containing solutions (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2746-2756 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface chemistry of GaAs passivated with P2S5 solutions modified with sulfur and other sulfides has been studied with x-ray photoelectron spectroscopy, room-temperature photoluminescence, scanning Auger electron spectroscopy, and scanning electron microscopy. The degree of passivity achieved was measured by determining the intensity of room-temperature photoluminescence before and after passivation. An increase in luminescence intensity of up to 23 times was observed after a treatment by solutions containing P2S5 and (NH4)2S buffered with sulfur due to reduced surface nonradiative carrier recombination. Phosphorus oxides and sulfur bound to the Ga and As species were present on the passivated surface. In addition, all the surfaces treated with sulfide solutions were covered to a variable extent with crystallized residues, and a treatment was devised to eliminate these residues while still retaining a passivated surface. Exposure of passivated surfaces to room-temperature air increased the amount of gallium bound to oxygen, while simultaneously reducing the concentration of As on the surface. Arsenic oxide was absent from solution passivated surfaces, even after three weeks in air, but was detected on surfaces passivated in ultrahigh vacuum (UHV) by either evaporation of solid sulfur or adsorption of hydrogen sulfide. Upon exposure to air, the luminescence intensity decreased from all sample whether passivated in UHV or in aqueous solutions; however, the rate and degree of degradation was dependent upon whether passivation was done in vacuum (severe) or by solution (better) and depended upon the exact solution composition. However, the barrier height of Au/GaAs Schottky contacts with passivated interfaces was not changed by exposure to air for times up to one week.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351048
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  • 3
    Electronic Resource
    Electronic Resource
    Degradation of field emission display phosphors (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 483-488 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Degradation of ZnS and Y2O2S cathodoluminescent (CL) phosphors has been studied at 1–4 keV using Auger electron spectroscopy simultaneous with CL. The data are consistent with an electron stimulated surface chemical reaction (ESSCR) which led to destruction of ZnS and formation of a surface nonluminescent ZnO layer as well as injection of oxygen point defects into the near-surface region. In the case of Y2O2S:Eu, the electron beam stimulated removal of S and formation of Y2O3:Eu in the presence of 1×10−6 Torr of oxygen. A model is presented which predicts that degradation by the ESSCR should increase with pressure in the vacuum, depend exponentially on electron dose, increase as the primary beam energy was reduced below 4 keV, and depend upon the type of gas present in the vacuum. These trends were demonstrated from the experimental data. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373683
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of the Ce+3 bonding in the Ca0.5Sr0.5Ga2S4:Ce phosphor via x-ray photoelectron spectroscopy (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 2377-2384 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The addition of oxygen in Ca0.5Sr0.5Ga2S4:Ce phosphor was found to nearly double the luminance and to blue shift the emission spectrum of the Ce+3 4f–5d transition. X-ray photoelectron spectroscopy (XPS) analysis was used to investigate the local chemistry of the Ce+3 luminescent center in the undoped and oxygen-doped Ca0.5Sr0.5Ga2S4 phosphor. The shake up structure in the Ce+3 3d3/2 and 3d5/2 XPS spectra is due to a ligand-to-metal charge transfer process, and the relative intensity of the charge transfer peaks increased when oxygen was introduced. Because the charge transfer probability is controlled by the local ionicity of the Ce bonds, the increase in the charge transfer peak intensity is consistent with the formation of Ce–O bonds. Furthermore, the binding energy of the charge transfer peaks and the Ce MNN Auger peak shifted, again consistent with oxygen bonding to the Ce+3 luminescent center. A self-consistent field configuration interaction model is used to calculate the positions of the 4f and 5d levels with Ce–S and Ce–O bonds. By replacing the three of eight sulfur ligands with oxygen the SCF/CI model predicted a 1035 cm−1 blue shift in the 4f–5d transition energy which was in excellent agreement with the observed 730 cm−1 blue shift. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371063
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of sputter cleaning on Au/GaAs contacts and the role of doping (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3568-3573 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of Ar-ion sputtering on electrical properties of Au contacts on (100) GaAs and the role of doping concentration have been studied. The n-GaAs was doped with 1017 or 1018 cm−3 Si or with 1018 cm−3 Te and the p-GaAs with 1018 or 1019 cm−3 Zn. After either chemical etching or Ar-ion beam cleaning of the GaAs, Au contacts were formed by evaporation in ultrahigh vacuum (10−9 Torr). Ion bombardment with Ar+ produced clean but nonstoichiometric, damaged GaAs surfaces. Contacts on chemically cleaned GaAs were either (nearly) ohmic or Schottky, depending upon the dopant and concentration. On sputtered GaAs, all the contacts showed soft rectification but did not act as purely Schottky contacts. The type of dopants, i.e., n or p, caused differences in the I-V behavior, but the behavior for different dopants of the same type was very similar. Sputtering increased the depletion depth on all the samples, and the depletion depth became larger as the ion energy increased and/or the dopant concentration decreased. The electrical behavior of the sputtered samples is suggested to result from the creation of a compensated layer with deep defect states. The deep level states are postulated to be related to defects resulting from sputtering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342632
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanism of forming ohmic contacts to GaAs (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 947-949 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The distribution of Si dopant at the Au/GaAs interface after heat treatment has been studied using spatially resolved secondary-ion mass spectrometry. Previously it has been shown that heat treatment changes as deposited Au thin film from Schottky contacts to ohmic contacts. The present study shows that the transition to an ohmic contact results from segregation of dopants in areas where GaAs is decomposed by reacting with the Au overlayer. Thus the ohmic contact is spatially very inhomogeneous at the metal/semiconductor interface. The mechanism leading to concentrations of the Si and nonuniform ohmic contacts is discussed, and segregation to the solid during decomposition of the GaAs is the most likely mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106310
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  • 7
    Electronic Resource
    Electronic Resource
    Bound exciton luminescence in Te-doped SrS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 3676-3683 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article describes the synthesis and characterization of SrS:Te powders which were found to have two high energy emission bands under photoluminescent excitation. To understand the radiative recombination mechanism, photoluminescence emission spectra were measured as a function of temperature. A simple configuration coordinate model was used to explain the emission band broadening and luminescence quenching that was observed with increasing temperature. Luminescence decay measurements were also performed, and the empirically determined transition rates were compared to theoretical calculations. Finally, SrS:Te ACTFEL devices were fabricated and tested under electroluminescence excitation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368544
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  • 8
    Electronic Resource
    Electronic Resource
    Room-temerature oxidation of Ni(110) at low and atmospheric oxygen pressures (1996)
    Springer
    Oxidation of metals 45 (1996), S. 301-321 
    Details
    ISSN: 1573-4889
    Keywords: nickel ; low-temperature oxidation ; surface-analytical techniques ; thin-film growth mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Oxidation of atomically clean (110) nickel single crystals has been studied at room temperature and in pure oxygen or air at pressures from 1×10−9 torr to atmospheric. X-ray photoelectron (XPS) and Auger electron spectroscopic (AES) data indicate that the standard regimes of dissociative chemisorption, oxide nucleation, and oxide lateral growth to coalescence were observed at low pressures. After the NiO layer coalesced at low pressures, exposure of the sample to atmospheric oxygen or air did not cause further growth of the oxide thickness at room temperature. Instead the growth of a high-energy shoulder on the O 1s XPS peak indicated the formation of Ni(OH)2 on the surface. The presence of the hydroxide is consistent with high-resolution, electronenergy-loss spectroscopy (HREELS) data and chemical shifts in the Ni 2p spectra. While the oxide thickness is constant, the hydroxide thickness increased with exposure and time at high pressure. Surface analysis and lowpressure techniques are appropriate for the study of room-temperature, ambient-oxide formation and allow a determination of the kinetics and reaction products critical to the passivation of Ni.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01046987
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of nitrogen and water vapor on the oxidation of thorium between 400 and 1000° C (1972)
    Springer
    Oxidation of metals 4 (1972), S. 27-34 
    Details
    ISSN: 1573-4889
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The reaction of thorium with air, oxygen, oxygen-nitrogen, and oxygen-water vapor atmospheres has been studied in the temperature range of 400–1000°C using thermogravimetric analysis and metallographic and x-ray diffraction examination. It was demonstrated that H2O and N2 as well as O2 are involved in the reaction of thorium with air. Oxidation in pure oxygen followed a relatively slow rate. Faster rates and nonisothermal conditions were observed under certain conditions with mixed atmospheres. Above 600° C,N2 caused accelerated oxidation and scale color changes. The effects of H2O were similar but occurred below 600°C. The rate laws followed for reaction with air are complex combinations of cubic, parabolic, and linear laws.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612505
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  • 10
    Electronic Resource
    Electronic Resource
    Quantitative surface analysis of layered materialsInvited paper presented at the Quantitative Surface Analysis (QSA-6) Conference, London, 13-16 November 1990. (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 18 (1992), S. 251-256 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The effects of concentration variation with depth, C(X), on the quantitative reduction of electron spectroscopic data is discussed. It is shown that when the concentration varies with depth, quantitation of the data is affected by the escape depth of the electron transitions chosen for quantitation. Therefore, accurate quantitation is impossible without knowledge of C(X). A Laplace transform method to determine C(X) from angle-resolved electron spectroscopic data is reviewed, along with potential problems caused by variation with angle of the escape depth of electrons in the solid, channeling, forward scattering, matrix corrections and surface roughness.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740180402
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