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  • 1
    Digitale Medien
    Digitale Medien
    Annealing studies of low-temperature-grown GaAs:Be (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1699-1707 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The isochronal and isothermal annealing characteristics of acceptor-doped GaAs:Be grown at low substrate temperatures (300 °C) by molecular-beam epitaxy (LTMBE) have been studied. The Be was introduced in a range of concentrations from 1016 to 1019 cm−3. Electrical measurements of as-grown material up to the highest Be concentration of 1019 cm−3 show that no free holes are contributed to the valence band even though Raman spectroscopy of the Be local vibrational mode indicates that the majority of the Be impurities occupy substitutional sites. It is proposed that Be acceptors are rendered inactive by the high concentration of AsGa-related native donor defects present in LTMBE material. The concentration of AsGa-related defects in the neutral charge state was estimated from infrared absorption measurements to be as high as 3×1019 cm−3. A distinct annealing stage at 500 °C, similar to that found in irradiation-damaged and plastically deformed GaAs, marks a rapid decrease in the concentration of AsGa-related defects. A second annealing stage near 800 °C corresponds to the activation of Be acceptors. The presence of gallium vacancies VGa was investigated by slow positron annihilation. Results indicate an excess concentration of VGa in LTMBE layers over bulk-grown crystals. Analysis of isothermal annealing kinetics for the removal of AsGa-related defects gives an activation energy of 1.7±0.3 eV. The defect removal mechanism is modeled with VGa-assisted diffusion of AsGa to As precipitates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.351200
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  • 2
    Digitale Medien
    Digitale Medien
    Effects of substrate temperature on chemical structure of amorphous carbon films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2243-2248 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Amorphous carbon thin films were prepared at 30, 200, and 450 °C by magnetron sputtering of a graphite target. The surface structure and chemical bonding (sp2/sp3) of the carbon films were characterized by scanning tunneling microscopy (STM) and Raman spectroscopy. STM images show that graphite microcrystallites of 20–40 A(ring) in size are present at the surfaces of all the films and the number of the microcrystallites increases with increasing substrate temperature. The microcrystallites often contain structural defects. Raman measurements show that increasing the substrate temperature results in an increase in the sp2-bonded fraction of carbon atoms and a decrease in the microstructural defects. These results indicate that the microstructural changes are correlated with changes in the chemical bonding ratio (sp3/sp3) and no diamond microcrystallites are present in the amorphous carbon. A three-dimensional atomic structure of the graphite microcrystallites is discussed in terms of turbostratic graphite.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.351122
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  • 3
    Digitale Medien
    Digitale Medien
    Temperature dependent mobility in single-crystal and chemical vapor-deposited diamond (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2888-2894 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The combined electron and hole mobility of a single-crystal type IIa natural diamond and a polycrystalline diamond film deposited by chemical vapor deposition (CVD) were measured using transient photoconductivity as a function of excitation density (1013–1017 cm−3) and temperature (120–410 K). In natural diamond the temperature dependence suggests that the mobility is limited by phonon scattering at low free carrier densities, and by electron-hole scattering at high densities. The combined electron and hole phonon-limited mobility at room temperature is 3000 (±500) cm2/V s. In the CVD film, the mobility at room temperature was estimated to be 50 cm2/V s at low excitation densities. The temperature dependence of the mobility-lifetime product at low excitation densities is different from that of natural diamond, and suggests that charged center scattering, rather than acoustic phonon scattering, is the dominant effect. High densities of nitrogen and dislocations are known to be present in the natural diamond, and these appear to be the dominant recombination sites which limit the carrier lifetime. In the polycrystalline film a variety of structural defects and impurities are believed to exist, but it is unknown which of these dominates the transport and recombination properties.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353018
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  • 4
    Digitale Medien
    Digitale Medien
    Raman and resistivity investigations of carbon overcoats of thin-film media: Correlations with tribological properties : 35th Annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5748-5750 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Tribological measurements have been performed on a series of carbon films deposited on untextured 95-mm magnetic disks by magnetron sputtering. Raman spectra and resistivity data of these films have been correlated to friction and wear performance. Tribochemical wear, as estimated by the rate of frictional buildup, is correlated to the G-band position in the Raman spectrum. Abrasive wear is best correlated to the I(D)/I(G) intensity ratio of the D and G bands, as well as to electrical resistivity. Interpretation of these data using structural models of amorphous carbon films is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347909
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  • 5
    Digitale Medien
    Digitale Medien
    The effect of coimplantation on the electrical activity of implanted carbon in GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7118-7123 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effects of radiation damage and stoichiometry on the electrical activity of carbon implanted in GaAs are studied. Damage due to implantation of an ion heavier than C increases the number of C atoms which substitute for As (CAs). Creation of an amorphous layer by implantation and the subsequent solid phase epitaxy during annealing further enhances the concentration of CAs. However, the free carrier concentration does not increase linearly with increasing concentration of CAs due to compensating defects. Activation of implanted C is maximized by maintaining the stoichiometry of the substrate which reduces the number of compensating defects in the crystal. Under optimum conditions for carbon implanted at a dose of 5×1014 cm−2, the carbon acceptor activity can be increased from 2% to 65% of the total implanted carbon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.355027
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  • 6
    Digitale Medien
    Digitale Medien
    Particle- and photoinduced conductivity in type-IIa diamonds (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1086-1095 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Electrical characteristics associated with radiation detection were measured on single-crystal natural type-IIa diamond using two techniques: charged particle-induced conductivity and time-resolved transient photoinduced conductivity. The two techniques complement each other: The charged particle-induced conductivity technique measures the product of the carrier mobility μ and lifetime τ throughout the bulk of the material while the transient photoconductivity technique measures the carrier mobility and lifetime independently at the first few micrometers of the material surface. For each technique, the μτ product was determined by integration of the respective signals. The collection distance that a free carrier drifts in an electric field was extracted by each technique. As a result, a direct comparison of bulk and surface electrical properties was performed. The data from these two techniques are in agreement, indicating no difference in the electrical properties between the bulk and the surface of the material. The collection distance continues to increase with field up to 25 kV/cm without saturation. Using the transient photoconductivity technique the carrier mobility was measured separately and compared with a simple electron-phonon scattering model. The general characteristics of carrier mobility, lifetime, and collection distance at low electric field appear to be adequately described by the model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354957
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  • 7
    Digitale Medien
    Digitale Medien
    Effect of nitrogen on the band structure of GaInNAs alloys (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 2349-2351 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We show that incorporation of nitrogen in Ga1−xInxAs to form Ga1−xInxNyAs1−y alloys leads to a splitting of the conduction band into two nonparabolic subbands. The splitting can be described in terms of an anticrossing interaction between a narrow band of localized nitrogen states and the extended conduction-band states of the semiconductor matrix. The downward shift of the lower subband edge accounts for the N-induced reduction of the fundamental band-gap energy. An analysis of the relationship between the subband splitting and the band-gap reduction demonstrates that the energetic location of the valence band is nearly independent of the N content in Ga1−xInxNyAs1−y alloys. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.371148
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  • 8
    Digitale Medien
    Digitale Medien
    Formation of diluted III–V nitride thin films by N ion implantation (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2227-2234 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Diluted III–Nx–V1−x alloys were successfully synthesized by nitrogen implantation into GaAs, InP, and AlyGa1−yAs. In all three cases the fundamental band-gap energy for the ion beam synthesized III–Nx–V1−x alloys was found to decrease with increasing N implantation dose in a manner similar to that observed in epitaxially grown GaNxAs1−x and InNxP1−x alloys. In GaNxAs1−x the highest value of x (fraction of "active" substitutional N on As sublattice) achieved was 0.006. It was observed that NAs is thermally unstable at temperatures higher than 850 °C. The highest value of x achieved in InNxP1−x was higher, 0.012, and the NP was found to be stable to at least 850 °C. In addition, the N activation efficiency in implanted InNxP1−x was at least a factor of 2 higher than that in GaNxAs1−x under similar processing conditions. AlyGa1−yNxAs1−x had not been made previously by epitaxial techniques. N implantation was successful in producing AlyGa1−yNxAs1−x alloys. Notably, the band gap of these alloys remains direct, even above the value of y (y〉0.44) where the band gap of the host material is indirect. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1388860
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  • 9
    Digitale Medien
    Digitale Medien
    Guanidines Derived from N-Cyanotetrahydroquinolines (1952)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 74 (1952), S. 3176-3177 
    Details
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ja01132a508
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  • 10
    Digitale Medien
    Digitale Medien
    High dose Cl implantation in ZnSe: Impurity incorporation and radiation damage (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1378-1383 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The structural characteristics of ZnSe thin films grown by organometallic vapor phase epitaxy and implanted heavily with Cl ions (5×1015 and 1×1016/cm2) were investigated using ion beam techniques, x-ray diffraction, and Raman spectroscopy. We have found that although the as-implanted ZnSe layers were severely damaged, no amorphous layer was formed with an implant dose as high as 1×1016 Cl ions/cm2. Crystalline damage in the ZnSe layers was not fully removed even after annealing at 700 °C for 10 s. Ion channeling reveals that after annealing over 50% of the Cl atoms sit substitutionally in the lattice and they are preferentially located in the Se site. However, a significant fraction of the substitutional Cl are found to be slightly displaced from the normal Se sites. The projected displacement was found to be ≈0.2 A(ring). Electrical measurements and Raman spectroscopy results suggest that a large concentration of Zn vacancies (VZn) are present in the annealed samples. We believe that the Cl displacement and the low conductivity in these samples are due to the formation of (ClSe−VZn) complexes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.356417
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