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  • 1
    Electronic Resource
    Electronic Resource
    Nitrogen uptake and rate-limiting step in low-temperature nitriding of iron (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 810-816 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, a method to nitride iron in NH3 ambients at low temperature (225–350 °C) has been developed. In this method, the Fe is covered with a thin (∼40 nm) Ni layer, which acts as a catalyst for the nitriding process. From experiments, in which the amount of nitrogen uptake is measured as a function of nitriding time, it is concluded that the decomposition of NH3 at the Ni surface contains the rate-limiting step in this low-temperature nitriding process. From a model calculation, it is further concluded that the reaction step NH3→NH2+H at the Ni surface is the rate-limiting step with an activation energy of ∼1.5 eV. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370808
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  • 2
    Electronic Resource
    Electronic Resource
    Prediction of phase formation sequence and phase stability in binary metal-aluminum thin-film systems using the effective heat of formation rule (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3636-3646 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effective heat of formation (ΔH') concept allows heats of formation to be calculated as a function of concentration. In this work the effective heat of formation rule is used to predict first phase formation in metal-aluminum thin-film systems and to predict subsequent phase sequence for thin metal films on thick aluminum or thin aluminum on thick metal substrates. The effective concentration at the growth interface is taken to be that of the lowest temperature eutectic (liquidus) for the binary system. Although the effective heat of formation rule may predict that formation of a certain phase would lead to the largest free energy change, this phase does not necessarily form at the moving reaction interface if it has difficulty to nucleate. By excluding phases with a large number of atoms per unit cell and which thus have difficulty to nucleate, the effective heat of formation rule successfully predicts first phase aluminide formation for all 15 metal-aluminum binary systems for which experimental data could be found. It is also shown how the effective heat of formation rule can be used to predict formation and decomposition of aluminide phases in contact with each other or in contact with their component metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349211
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  • 3
    Electronic Resource
    Electronic Resource
    A new magnetic multilayer system: Iron-bismuth (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 701-704 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic Fe-Bi multilayers have been, for the first time, synthesized by using electron-beam evaporation at 140 K. The relationships between film structure and magnetic properties were investigated by means of measurements of magnetization, x-ray diffraction, electron diffraction, and Mössbauer spectra. Films are ferromagnetic or paramagnetism, depending on Fe layer thickness, tFe. Films with tFe of about 1 nm exhibit perpendicular magnetic anisotropy while these with the thicker tFe have in-plane magnetism. Temperature dependence of magnetization in the Fe-Bi multilayers was also studied in the temperature range of 77–600 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346801
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  • 4
    Electronic Resource
    Electronic Resource
    Diffusion of dopants in B- and Sb-delta-doped Si films grown by solid-phase epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3150-3155 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion of δ-function-shaped B- and Sb-dopant spikes in thin Si films grown by solid-phase-epitaxy [(SPE), growth of amorphous film by molecular-beam epitaxy (MBE) at room temperature and subsequent regrowth in situ] during annealing in vacuum is compared to diffusion in films grown by low-temperature (LT) MBE. Diffusion temperatures from 750 to 900 °C, and two-dimensional concentrations of 0.7–1.6×1014 cm−2 have been investigated. The diffusive behavior of dopants in SPE films is found to be qualitatively different from that in films grown by LTMBE. This is related to the vacancylike defects that are intrinsic to growth by SPE but not to growth by LTMBE. Dopant profiles widen significantly during SPE regrowth, making the achievement of δ-function dopant spikes impossible. After a vacuum anneal the diffusion coefficients for both n- and p-type dopants are lower in SPE films than the corresponding values in films grown by LTMBE by up to one order of magnitude. The diffused depth profile of the dopant in LTMBE films shows the characteristic deviation from a pure Gaussian that is expected due to the concentration dependence of diffusion, i.e., a flat top and steep shoulders. In contrast, dopant depth profiles of SPE-grown material show after diffusion a central spike and relatively flat shoulders. The width of the central spike is, after an initial transient that it was not possible to resolve, independent of diffusion time and temperature. This indicates that the SPE material is defective, with the defects acting as traps during diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354583
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  • 5
    Electronic Resource
    Electronic Resource
    MeV ion implantation of N into Ti for surface hardening (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2152-2154 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructural and hardening effects of MeV N+ ion implanted into Ti have been examined and compared to the results of hundred keV implantations. Rutherford backscattering spectrometry shows that concentrations of up to 50 at. % N are easily built up for μm depths in Ti targets. X-ray diffraction gives evidence for the formation of titanium nitride (TiN). An increase in surface hardness of 30% using loads as heavy as 100 g was observed in the MeV-implanted specimens, while no hardening effects could be detected using these loads in the case of implantations with about hundred keV energies. This discovery in which MeV N implantation can form hardened layers of μm thickness on metals with higher load-carrying ability than that of hundred keV implanted species should be able to extend the application scope of the N implantation technique in the metallurgical field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100302
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  • 6
    Electronic Resource
    Electronic Resource
    Low-temperature nitriding of iron through a thin nickel layer (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1245-1247 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a new method for nitriding iron at low temperatures. First, iron is coated with a thin layer of nickel (∼36 nm), after which it is exposed to an NH3 atmosphere at temperatures below 300 °C. Underneath the nickel layer ε-Fe3−xN is formed at temperatures as low as 225 °C, while uncovered iron samples show a large uptake of oxygen after the same treatment. The nickel layer prevents the oxidation of iron by impurities in the NH3 gas, and acts as a catalyst for the decomposition of NH3. After decomposition the atomic nitrogen diffuses through the nickel layer towards the iron. With the process described, pore-free iron nitrides can be formed at low temperatures. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118542
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  • 7
    Electronic Resource
    Electronic Resource
    Luminescence quenching in erbium-doped hydrogenated amorphous silicon (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 997-999 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogenated amorphous silicon thin films are doped with erbium by ion implantation. Room-temperature photoluminescence at 1.54 μm, due to an intra-4f transition in Er4+, is observed after thermal annealing at 300–400 °C. Excitation of Er3+ is shown to be mediated by photocarriers. The Er3+ luminescence intensity is quenched by a factor of 15 as the temperature is raised from 10 K to room temperature. Codoping with oxygen (1 at. %) reduces the luminescence quenching to a factor of 7. The quenching is well correlated with a decrease in luminescence lifetime, indicating that nonradiative decay of excited Er3+ is the dominant quenching mechanism as the temperature is increased. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116124
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  • 8
    Electronic Resource
    Electronic Resource
    Luminescence quenching in erbium-doped hydrogenated amorphous silicon (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 46-48 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogenated amorphous silicon thin films are doped with erbium by ion implantation. Room-temperature photoluminescence at 1.54 μm, due to an intra-4f transition in Er4+, is observed after thermal annealing at 300–400 °C. Excitation of Er3+ is shown to be mediated by photocarriers. The Er3+ luminescence intensity is quenched by a factor of 15 as the temperature is raised from 10 K to room temperature. Codoping with oxygen (1 at. %) reduces the luminescence quenching to a factor of 7. The quenching is well correlated with a decrease in luminescence lifetime, indicating that nonradiative decay of excited Er3+ is the dominant quenching mechanism as the temperature is increased. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116751
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  • 9
    Electronic Resource
    Electronic Resource
    Giant enhancement of luminescence intensity in Er-doped Si/SiO2 resonant cavities (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1381-1383 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si/SiO2 Fabry–Pérot microcavities with rare-earth-doped SiO2 active regions are realized for the first time. Cavity-quality factors exceeding Q=300 are achieved with structures consisting of two Si/SiO2 distributed Bragg reflectors and an Er-implanted (λ/2) SiO2 active region. The room-temperature photoluminescence intensity of the on-axis emission is 1–2 orders of magnitude higher for resonant cavity structures as compared to structures without a cavity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107544
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  • 10
    Electronic Resource
    Electronic Resource
    Time dependence of dopant diffusion in δ-doped Si films and properties of Si point defects (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 312-314 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion of Sb and B in thin Si films grown by low temperature molecular beam epitaxy is investigated in the temperature range 750–900 °C for times of 0.25–60 h. The small spatial extent of the initial δ-function-like dopant profiles allows the detection of very small diffusional displacements. The dopant atoms are used as tracers of Si point defects (vacancies and self-interstitials). Diffusion of Sb is found to be enhanced relative to equilibrium values, while that of B is retarded. We propose a model based on an initial supersaturation of vacancies. Matching this model to the experimental data allows the extraction of the vacancy diffusivity, the activation energy of vacancy formation, and the recombination lifetime of interstitials. The results show that interstitial and vacancy populations cannot be considered independent at low temperature, as has been previously suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111189
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