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  • 1
    Electronic Resource
    Electronic Resource
    Metal Schottky barrier contacts to alpha 6H-SiC (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4757-4760 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation of Schottky barrier contacts to n-type 6H-SiC for a number of metals chosen to include a variety of physical and chemical properties has been investigated. The metals (Pd, Au, Ag, Tb, Er, Mn, Al, and Mg) were deposited onto room temperature surfaces terminated with a submonolayer coverage of oxygen. The metal/6H-SiC interface chemistry and Schottky barrier height φB during contact formation were obtained with x-ray photoemission spectroscopy; the electrical properties of subsequently formed thick contacts were characterized by current-voltage and capacitance-voltage techniques. The øB values for these metals extend over a wide 1.3 eV range. To a varying degree φB depends on the 6H-SiC crystal face (Si vs C). Mg and Al (Si face of latter) have φB=0.3 eV, a value which is suitable for nonalloyed ohmic contacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352086
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  • 2
    Electronic Resource
    Electronic Resource
    The role of geometric considerations in the diamond-cubic boron nitride heteroepitaxial system (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2679-2681 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the methods and results of a theoretical study of the diamond-cubic boron nitride [BNcub] heteroepitaxial system. We introduce a general, geometric reciprocal space technique for evaluating candidate epitaxial configurations, and a novel system of essentially geometric criteria to order them from most to least likely to occur. In the diamond- BNcub system, it is found that low index like planes require a relatively small strain of 1.37% from bulk parameters. The unlike epitaxial configuration which pairs diamond{100} with BNcub{221} and yields two-dimensional coincidence with the same strain is favored above other low index mixed configurations. The essentially geometric nature of this epitaxial system is highlighted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348663
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  • 3
    Electronic Resource
    Electronic Resource
    A high-energy spherical grating monochromator for soft x rays at the Daresbury SRS (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4349-4353 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A vertically dispersing high-energy spherical grating monochromator (HESGM) has been installed on the synchrotron radiation source (SRS) at the Daresbury Laboratory. The instrument has no entrance slit and provides a high intensity source of x rays of energy 250–1400 eV focused into a small spot suitable for surface spectroscopy. Photoabsorption features of 240 meV have been resolved, but the resolution of the instrument is dependent on the SRS stored beam current. The degree of linear polarization has been measured at the carbon K edge to be 0.80.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143735
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of ionization energies of the nitrogen donors in 6H-SiC by admittance spectroscopy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1956-1958 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nitrogen donor levels have been studied by admittance spectroscopy between 20 and 200 K in Schottky barriers made on lightly n-type epitaxial 6H-SiC layers. Measurements at different frequencies yield different freezeout temperatures which in turn are used to determine the donor level energies. Two electron traps at Ec−0.082 eV and at Ec−0.140 eV were detected. These levels are associated with nitrogen, respectively, at the hexagonal sites for the former and at the cubic sites for the latter level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357655
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  • 5
    Electronic Resource
    Electronic Resource
    New rare-earth intermetallic phases R3(Fe,M)29Xn: (R=Ce, Pr, Nd, Sm, Gd; M=Ti, V, Cr, Mn; and X=H, N, C) (invited) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6138-6143 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: New rare-earth (R), iron-rich ternary intermetallic compounds of the form R3(Fe,M)29 with the monoclinic Nd3(Fe,Ti)29 structure (space group P21/c, #14, Z=2) have recently been shown to form with R=Ce, Nd, Pr, Sm, and Gd, and M=Ti, V, Cr, and Mn. This novel structure is derived from the alternate stacking of Th2Zn17 and ThMn12-type segments and contains two R sites and fifteen Fe(M) sites. Reported Curie temperatures of the 3:29 compounds range from 296 K (R=Ce, M=Cr) to 524 K (R=Sm, M=V). The 3:29 compounds all show improved magnetic properties after interstitial modification with H or N; in particular, room-temperature coercivity has been reported in Sm3(Fe,Ti)29N5, making this compound a candidate for possible permanent-magnet applications. In this article we will review the work carried out to date on the 3:29 compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358333
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  • 6
    Electronic Resource
    Electronic Resource
    Low energy ion-assisted deposition of titanium nitride ohmic contacts on alpha (6H)-silicon carbide (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2868-2870 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low energy (100 eV) ion-assisted reactive evaporation was used to deposit titanium nitride (TiN) onto single crystal α(6H)-silicon carbide (SiC) wafers to investigate the potential of the former for electrical contacts. Theoretical considerations indicate that TiN (work function of 3.74 eV) should form an ohmic contact with SiC [work function of 4.8 eV for the (0001) face] provided an oxide-free interface can be obtained. Activated nitrogen was used to clean the SiC surface prior to deposition, while Auger spectroscopy and current-voltage (I-V) measurements were used to assess oxygen concentration at the interface and contact character, respectively. The contacts were ohmic after deposition. Little change was observed after annealing at 450 and 550 °C for 15 min.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105836
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  • 7
    Electronic Resource
    Electronic Resource
    Observation of a negative electron affinity for heteroepitaxial AlN on α(6H)-SiC(0001) (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3288-3290 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This study demonstrates the presence of a negative electron affinity (NEA) surface on AlN was grown on α(6H)-SiC. Heteroepitaxial AlN was grown on α(6H)-SiC(0001) substrates by molecular beam epitaxy techniques. The surface electronic states were characterized by ultraviolet photoemission obtained at surface normal. The observation of a sharp spectral feature at the lowest energy of the emitted electrons is an indication of a surface with a negative electron affinity. In addition, the trend of the NEA feature was examined as a function of annealing. The surface Fermi level is found to be near the middle of the AlN gap, and a possible band alignment between the AlN and SiC is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111312
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  • 8
    Electronic Resource
    Electronic Resource
    Spin-up in a rectangular container (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 150-159 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spin-up from rest of (i) a homogeneous and (ii) a linearly stratified fluid in a rectangular container has been examined in the laboratory. In the spin-up process leading to the ultimate state of rigid-body rotation, three main stages can be discerned, these being (1) the starting flow, characterized by zero absolute vorticity, (2) flow separation due to cyclonic vorticity generation at the lateral tank walls, and (3) a subsequent organization of the flow into a regular array of alternately cyclonic and anticyclonic cells. During the final stage the flow in these cells gradually decays due to the spin-down/spin-up mechanism provided by the Ekman boundary layer present at the bottom of each cell. Experiments have been performed with free-surface and rigid-lid upper boundary conditions, and the organization of the flow in these cases was observed to be essentially different. In particular, it was noted that the central cell in the free-surface case is always cyclonic. A model for this behavior is advanced, in terms of the tendency of cyclonic vortices to move toward the rotation axis in the free-surface configuration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857764
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  • 9
    Electronic Resource
    Electronic Resource
    The high energy spherical grating monochromator−A new source of soft x rays at Daresbury (abstract) : Proceedings of the 4th international conference on synchrotron radiation instrumentation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 1341-1341 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article we report the characteristics of the new High Energy Spherical Grating Monochromator beam line on the SRS. The instrument, which has no entrance slit, was designed to provide high photon flux with small spot size, in the energy range covering the 1s binding energies of carbon, nitrogen, oxygen, and fluorine. Radiation from a bending magnet is horizontally focused onto the exit slit by a long, Pt-coated meridian cylinder (R=299 m, 2 mrad horiz. aperture, 2° glancing angle). The light is vertically diffracted and focused by one of three interchangeable spherical gratings (1050, 1500, and 1800 lines mm−1) operating in negative order. Finally, the light is refocused by an ellipsoidal mirror. The photon flux, determined with copper and carbon photocathodes, is presented for the three gratings. Useful flux is obtained in the range 250–1200 eV, with intensity maxima for each grating at 600, 700, and 800 eV of 11, 9, and 5×1010 photons s−1 per 100-mA stored beam into a band pass of 0.05%. The influence of contaminants which are present on the optical elements is discussed, together with details of beam line operating conditions which minimize the build up of such contaminants. Photoabsorption and photoemission measurements indicate a high (up to 30%) second order and some third order light content. Resolution determinations obtained from photoabsorption measurements are presented. Although features as narrow as 250 meV have been resolved, the resolving power of the instrument is found to depend strongly on stored beam current. We suggest this may be due to electron beam (i.e., source) blow-up. We critically discuss the suitability of the new facility for surface EXAFS of low Z adsorbates, in particular above the carbon, nitrogen, and oxygen 1s edges, using examples from recent studies which have been undertaken on the beamline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143064
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  • 10
    Electronic Resource
    Electronic Resource
    Design and performance of an electron cyclotron resonance plasma source for standard molecular beam epitaxy equipment (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2407-2411 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electron cyclotron resonance plasma source which can be inserted into a 2.25-in.-diam. sleeve designed for standard molecular beam epitaxy effusion cells has been designed and commissioned. This source uses a coaxial microwave line structure, with an external tuner and small electromagnets for the production of the resonance and extraction magnetic fields. It also provides the same source-to-substrate distance as other sources which eliminates wall collisions and resulting recombination of active species. The source exhibits stable and continuous operation over four decades of pressure and gridless plasma beam extraction. The low-pressure characteristics of the plasma beam for nitrogen (hydrogen) include an ion current density of 0.2 (1.0) mA/cm2, an ion density of 4×109 (5×1010) cm−3, an electron temperature of 120 000 (70 000) K over a 3-in. wafer located 20 cm from the source. This source has been successfully used to grow thin films of GaN and AlN and layered structures of these two materials on SiC and sapphire substrates at temperatures as low as 400 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141371
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