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  • 1
    Electronic Resource
    Electronic Resource
    Defect dominated charge transport in amorphous Ta2O5 thin films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 850-862 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ta2O5 is a candidate for use in metal–oxide–metal (MOM) capacitors in several areas of silicon device technology. Understanding and controlling leakage current is critical for successful implementation of this material. We have studied thermal and photoconductive charge transport processes in Ta2O5 MOM capacitors fabricated by anodization, reactive sputtering, and chemical vapor deposition. We find that the results from each of these three methods are similar if one compares films that have the same thickness and electrodes. Two types of leakage current are identified: (a) a transient current that charges the bulk states of the films and (b) a steady state activated process involving electron transport via a defect band. The transient process involves either tunneling conductivity into states near the Fermi energy or ion motion. The steady state process, seen most commonly in films 〈300 Å thick, is dominated by a large number of defects, ∼1019–1020 cm−3, located near the metal–oxide interfaces. The interior of thick Ta2O5 films has a substantially reduced number of defects. Modest heating (300–400 °C) of Ta2O5 in contact with a reactive metal electrode such as Al, Ti, or Ta results in interfacial reactions and the diffusion of defects across the thickness of the film. These experiments show that successful integration of Ta2O5 into semiconductor processing requires a better understanding of the impact of defects on the electrical characteristics and a better control of the metal–Ta2O5 interface. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373747
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  • 2
    Electronic Resource
    Electronic Resource
    Asymmetrically cut crystals as optical elements for highly collimated x-ray beams : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1506-1509 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Asymmetrically cut perfect crystals, in both the Laue and Bragg geometries, are examined as single crystal monochromators for x-ray beams that are collimated to a small fraction of the Darwin width, as is typical in experiments with coherent x rays. Both the Laue and asymmetric Bragg geometries are plagued by an inherent chromatic aberration that increases the beam divergence much beyond that of the symmetric Bragg geometry. Measurements from a recent experiment at the ESRF are presented to compare Si(220) (symmetric Bragg), diamond(111) (asymmetric Laue), and diamond(111) (symmetric Bragg inclined) geometries. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145892
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  • 3
    Electronic Resource
    Electronic Resource
    Deposition and properties of NiFe2O4 thin films (abstract) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6124-6124 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the properties of NiFe2O4 thin films prepared by laser ablation of a stoichiometric NiFe2O4 target. Textured polycrystalline films were obtained on a-SiO2 as well as on various substrates with Au, Ag, Pt, and MgF2 buffer layers. Epitaxially oriented films were obtained on MgO, (11¯02)-oriented Al2O3, (112¯0)-oriented Al2O3, Y-stabilized ZrO2 (YSZ), and SrTiO3, although the crystalline quality of the films varied. Contamination by diffusion from the substrate and strains induced by both lattice constant mismatch and differential thermal expansion degraded the magnetic properties of the films, and in some cases decreased the electrical resistivity as well. By choosing the right substrate (YSZ), temperature (600 °C), and PO2 (0.01 mT), we are able to prepare epitaxial films with bulk saturation magnetization (Ms=270 G) and fairly low anisotropy (K∼105 erg/cm3) as inferred by torque magnetometry. These films and bilayers are expected to be useful in a variety of fundamental investigations as well as having the potential for technological applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355481
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  • 4
    Electronic Resource
    Electronic Resource
    Nitrogen plasma annealing for low temperature Ta2O5 films (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1308-1310 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A low temperature oxygen/nitrogen plasma process is reported that substantially reduces leakage currents in chemical vapor deposited (CVD) and physical vapor deposited (PVD) films of tantalum oxide. We show that a combination of nitrogen and oxygen in a remote downstream microwave plasma source reduces leakage currents in CVD films of tantalum oxide and also reduces trap densities as measured by charge pumping. The as deposited CVD films show a high level of photoluminescence that is substantially lowered by the plasma anneal due to a reduction in the density of midgap states. For films deposited by PVD in the thickness range of 100 nm we find low leakage currents with a substantial improvement from the introduction of nitrogen into the plasma. However, PVD films in the thickness range of 20 nm show larger relative leakage currents and less of an improvement from the addition of nitrogen. The role of nitrogen in lowering leakage currents and charge trapping is thought to occur from a reduction in the density of bulk trap states in the oxide due to partial incorporation of nitrogen in the oxide. Both of these low temperature deposition and annealing processes are compatible with integration into the upper levels of metallization for high density circuits.© 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120569
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  • 5
    Electronic Resource
    Electronic Resource
    In situ epitaxial growth of Y1Ba2Cu3O7−x films by molecular beam epitaxy with an activated oxygen source (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2683-2685 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Highly oriented, epitaxial Y1Ba2Cu3O7−x thin films were prepared on MgO(100) by molecular beam epitaxy at a substrate temperature of 550–600 °C. The in situ growth was achieved by incorporating reactive oxygen species produced by a remote microwave plasma in a flow-tube reactor. The epitaxial (001) orientation is demonstrated by x-ray diffraction and ion channeling. In situ reflection high-energy electron diffraction showed that a layer-by-layer growth has produced a well-ordered, atomically smooth surface in the as-grown tetragonal phase of an oxygen stoichiometry of 6.2–6.3. A 500 °C anneal in 1 atm of O2 converted the oxygen content to 6.7 to 6.8. Typical superconducting transport properties of an Y1Ba2Cu3O7−x film 1000 A(ring) thick are ρ(300 K)=325 μΩ cm, ρ(300 K)/ρ(100 K)=2.4, Tc(onset)=92 K, and Tc(R=0)=82 K. The transport Jc at 75 K is 1×105 A/cm2, and increases to 1×106 A/cm2 at 70 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100545
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  • 6
    Electronic Resource
    Electronic Resource
    Preparation of high Tc and Jc films of Ba2YCu3O7 using laser evaporation of a composite target containing BaF2 (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1995-1997 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High Tc and Jc superconducting films of Ba2YCu3O7 are prepared on SrTiO3 〈100〉 substrates using pulsed excimer laser evaporation of a composite target containing BaF2, Y2O3, and CuO, followed by annealing in wet oxygen. High transition temperatures (R=0 from 89.5 to 91 K) and high critical current densities (Jc≥7×105 A cm−2) are obtained. The electrical transport properties of these films are significantly better than films previously grown via laser ablation of Ba-Y-Cu-O targets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99745
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxy of superconducting (Rb,Ba)BiO3 (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2120-2122 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The simple cubic perovskite (Rb,Ba)BiO3 can be grown at temperatures below 350 °C by molecular beam epitaxy using a rf plasma atomic oxygen source. Films with superconducting onsets in resistivity as high as 27 K are obtained without annealing. The epitaxy proceeds in the normal (100) orientation on {100} SrTiO3, despite a 10% lattice mismatch. (110) epitaxy and spotty reflection high-energy electron diffraction (RHEED) patterns are obtained on {100} MgO substrates, despite the good lattice match for (100) growth. Streaked and spotty RHEED patterns have been obtained on either substrate. Sticking coefficients for bismuth depend on the growth conditions, indicating that the epitaxy is partially controlled by desorption kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102343
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  • 8
    Electronic Resource
    Electronic Resource
    Observation of a halide (F/Cl) stabilized, new perovskite phase in superconducting Y2Ba5Cu7Ox films (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1625-1627 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new, ordered perovskite structure was stabilized as a majority phase in superconducting Y2Ba5Cu7O20−δ'(F/Cl)δ‘ films epitaxially grown on SrTiO3(100). The new phase was formed via fluorination or chlorination introduced during the post-deposition O2 furnace anneal for recrystallization. The structure is determined by x-ray diffraction to be an orthorhombic unit cell [a∼b=3.86(1) A(ring), c=27.24(6) A(ring)] with reflection conditions consistent with a fully twinned A-centered cell. Films containing primarily the new phase show a lower resistivity ρ(300 K)∼177 μΩ cm, a comparable ratio of ρ(300 K)/ρ(100 K)∼3.0, and a lower superconducting temperature of 78–74 K when compared to Y1Ba2Cu3O7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99704
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  • 9
    Electronic Resource
    Electronic Resource
    Anisotropic critical current density in superconducting Bi2Sr2CaCu2O8 crystals (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 72-74 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Critical current densities and resistivities were measured in a single crystal of the high Tc superconductor Bi2Sr2CaCu2O8 within the ab basal plane ((parallel)) and along the c direction (⊥). A large anisotropy in critical current density is found, Jc(parallel)/Jc⊥≈103, in quantitative agreement with the large normal-state resistivity anisotropy near Tc. The data provide strong evidence for a two-dimensional layered structure of metallic planes separated by semi-insulating barriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101437
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  • 10
    Electronic Resource
    Electronic Resource
    Ion beam thinning and polishing of YBa2Cu3O7 films (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1915-1917 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Successive ion beam milling at grazing angles of a 2400-A(ring)-thick, c-axis-oriented YBa2Cu3O7 film is shown to give smooth films which superconduct at thicknesses on the order of tens of angstroms. The thinning and polishing process is characterized at successive milling stages using resistance transitions, x-ray analysis, scanning electron microscopy, and Rutherford backscattering and channeling analysis of composition and surface quality. As thinning proceeds, scanning electron microscopy and diffraction features associated with a-axis texture are removed and crystalline quality, as measured by x rays and channeling, markedly improves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102331
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