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  • 1
    Electronic Resource
    Electronic Resource
    Effect of pretreatment process parameters on diamond nucleation on unscratched silicon substrates coated with amorphous carbon films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 485-492 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Diamond nucleation on unscratched silicon substrates was investigated using a conventional microwave plasma-enhanced chemical vapor deposition system. Silicon substrates were coated with thin films of amorphous carbon using a vacuum arc technique. The carbon-coated silicon substrates were pretreated with a methane-rich plasma at relatively low temperatures and were subsequently exposed to the diamond nucleation conditions. The significance of the pretreatment on the diamond nucleation density was examined by varying the methane concentration, chamber pressure, and exposure time. Scanning electron microscopy demonstrated that densely packed spherical nanoparticles on the pretreated surfaces played the role of diamond nucleation seeds. Raman spectroscopy analysis showed that the nucleation seeds consisted of nonhydrogenated carbon and that their structure was influenced by the pretreatment conditions. Transmission electron microscopy revealed that the nucleation seeds comprised disordered graphitic carbon and ultrafine diamond crystallites. Submicrometer films of good quality diamond possessing significantly higher nucleation densities (∼5×1010 cm−2) were grown from nanoparticles produced under optimum pretreatment conditions. The enhancement of the diamond nucleation density is mainly attributed to the formation of a large number of nanoparticles, which provided sufficient high-surface free-energy sites for diamond nucleation, in conjunction with their high etching resistance to atomic hydrogen stemming from the significant percentage of sp3 atomic carbon configurations, as evidenced by the presence of nanocrystalline diamond in the nanoparticle structure. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360855
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  • 2
    Electronic Resource
    Electronic Resource
    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
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356417
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  • 3
    Electronic Resource
    Electronic Resource
    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
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1388860
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  • 4
    Electronic Resource
    Electronic Resource
    Annealing of nonhydrogenated amorphous carbon films prepared by filtered cathodic arc deposition (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 2395-2399 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of postdeposition annealing to 600 °C in vacuum on the hardness, modulus, film stress, and sp3 content of nonhydrogenated amorphous carbon was studied. The films were deposited using a filtered cathodic arc source and the film properties were varied by controlling the substrate bias. In films with an initial sp3 content of greater than 80% a significant decrease (from 10.5 GPa to less than 2 GPa) in the level of compressive stress was observed without deterioration of the mechanical properties. In films with an initial sp3 content of 50%, the stress and hardness remained constant. Films with lower sp3 content showed a significant increase in the level of stresses and only a marginal decrease in hardness. The evolution of stresses and hardness with annealing is discussed in light of a proposed microstructure of these amorphous films. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288221
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  • 5
    Electronic Resource
    Electronic Resource
    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
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371148
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  • 6
    Electronic Resource
    Electronic Resource
    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
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354957
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  • 7
    Electronic Resource
    Electronic Resource
    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
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351122
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  • 8
    Electronic Resource
    Electronic Resource
    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
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347909
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  • 9
    Electronic Resource
    Electronic Resource
    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
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355027
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  • 10
    Electronic Resource
    Electronic Resource
    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
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353018
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