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  • 1
    Digitale Medien
    Digitale Medien
    Microstructure of ultrananocrystalline diamond films grown by microwave Ar–CH4 plasma chemical vapor deposition with or without added H2 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 118-122 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ultrananocrystalline diamond (UNCD) films, grown using microwave plasma-enhanced chemical vapor deposition with gas mixtures of Ar–1%CH4 or Ar–1%CH4–5%H2, have been examined with transmission electron microscopy (TEM). The films consist of equiaxed nanograins (2–10 nm in diameter) and elongated twinned dendritic grains. The area occupied by dendritic grains increases with the addition of H2. High resolution electron microscopy shows no evidence of an amorphous phase at grain boundaries, which are typically one or two atomic layer thick (0.2–0.4 nm). Cross-section TEM reveals a noncolumnar structure of the films. The initial nucleation of diamond occurs directly on the Si substrate when H2 is present in the plasma. For the case of UNCD growth from a plasma without addition of H2, the initial nucleation occurs on an amorphous carbon layer about 10–15 nm thick directly grown on the Si substrate. This result indicates that hydrogen plays a critical role in determining the nucleation interface between the UNCD films and the Si substrate. The relation between diamond nuclei and Si is primarily random and occasionally epitaxial. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1377301
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  • 2
    Digitale Medien
    Digitale Medien
    Electron field emission for ultrananocrystalline diamond films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2958-2967 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ultrananocrystalline diamond (UNCD) films 0.1–2.4 μm thick were conformally deposited on sharp single Si microtip emitters, using microwave CH4–Ar plasma-enhanced chemical vapor deposition in combination with a dielectrophoretic seeding process. Field-emission studies exhibited stable, extremely high (60–100 μA/tip) emission current, with little variation in threshold fields as a function of film thickness or Si tip radius. The electron emission properties of high aspect ratio Si microtips, coated with diamond using the hot filament chemical vapor deposition (HFCVD) process were found to be very different from those of the UNCD-coated tips. For the HFCVD process, there is a strong dependence of the emission threshold on both the diamond coating thickness and Si tip radius. Quantum photoyield measurements of the UNCD films revealed that these films have an enhanced density of states within the bulk diamond band gap that is correlated with a reduction in the threshold field for electron emission. In addition, scanning tunneling microscopy studies indicate that the emission sites from UNCD films are related to minima or inflection points in the surface topography, and not to surface asperities. These data, in conjunction with tight binding pseudopotential calculations, indicate that grain boundaries play a critical role in the electron emission properties of UNCD films, such that these boundaries: (a) provide a conducting path from the substrate to the diamond–vacuum interface, (b) produce a geometric enhancement in the local electric field via internal structures, rather than surface topography, and (c) produce an enhancement in the local density of states within the bulk diamond band gap. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1320009
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  • 3
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of Pb (ZrxTi1−x)O3 thin films produced by an automated laser ablation deposition technique (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5197-5207 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ferroelectric lead zirconium titanate [Pb (ZrxTi1−x)O3] (PZT) thin films have been synthesized by using an automated laser ablation deposition technique with a capability for layer-by-layer or simultaneous deposition of elemental film constituents. The technique is suitable for producing multicomponent and/or multilayered thin films with controlled stoichiometry, such as high-temperature superconductor, ferroelectric, and electro-optic thin films. PZT films were synthesized on MgO (100) by either sequential deposition of layers of ZrO2, TiO2, and PbO, produced by laser ablation of ZrO2, TiO2, and PbO targets, or by simultaneous deposition of all species from ablation of stoichiometric or PbO-rich PZT targets. Films were deposited at 200 °C and subsequently annealed at 600 °C for different periods of time. The orientation, microstructure, surface topography, and composition of the films were characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Rutherford backscattering spectrometry, respectively. As-deposited layer films consists of highly oriented (001) PbO layers, from which highly oriented (110) PZT films are produced after postdeposition annealing. On the other hand, laser ablation of bulk PZT targets yields amorphous as-deposited films, which evolve into highly oriented (100) PZT films after postdeposition annealing. Preliminary electrical characterization of the PZT films included polarization hysteresis, fatigue, conductivity (ac and dc), and capacitance versus voltage measurements. From the initial electrical measurements, it appears that the remnant polarization of the layered PZT films is similar to that of the films produced by laser ablation of bulk PZT targets.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353746
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  • 4
    Digitale Medien
    Digitale Medien
    YBa2Cu3O7−δ films deposited by a novel ion beam sputtering technique (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 301-303 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Superconducting films of YBa2Cu3O7−δ have been synthesized in a novel ion beam sputter deposition system which features a rotating target holder with BaO2, CuO, and Y2O3 as the sputtering targets. The dwell time of the ion beam on each oxide target is determined by a computer-controlled feedback loop using the signal from a programmable quartz crystal resonator. The sputtered fluxes of all film components originate from the same spatial location, ensuring homogeneous film composition. The results presented demonstrate for the first time an automated ion beam sputter deposition system with the capability of producing high Tc superconducting films by controlled sputtering of either elemental metallic components or oxide precursors. The concept may be extended to include processes such as patterning, production of layered structures (junctions), and film encapsulation necessary for microcircuit manufacturing based on high Tc superconducting films.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101568
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  • 5
    Digitale Medien
    Digitale Medien
    Surface compositional and topographical changes resulting from excimer laser impacting on YBa2Cu3O7 single phase superconductors (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 239-241 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Superconducting pressed pellets of YBa2Cu3O7 (Tc=90 K), which were used as ablation targets for laser-induced vapor deposition of high Tc(85 K) superconducting thin films, have been analyzed by secondary electron microscopy, scanning Auger microscopy, energy dispersive x-ray analysis, and x-ray diffractometry. The elemental distribution of Y, Ba, and Cu appears reasonably uniform at depths corresponding to that probed by energy dispersive x-ray analysis (∼1 μm). However, scanning Auger microscopy analysis of the laser-impacted area shows a significant depletion of Cu and spatial redistribution of Y, Ba, Cu, and O on the target surface. X-ray diffractometry of the laser-impacted area shows the appearance of a new broad peak at a diffraction angle 2θ=29.7°, characteristic of BaY2O4 and a poorly defined peak at 2θ=29.3°, that can be attributed to BaCuO2. A possible influence of the laser-induced bulk superconductor compositional changes on the film composition is discussed in relation to recently reported experimental results on laser vapor deposition of high Tc films.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99508
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  • 6
    Digitale Medien
    Digitale Medien
    Low voltage electron emission from calcium carbonate whiskers coated with a thin layer of gold (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4051-4054 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Cold cathode electron field emission from aragonite CaCO3 whiskers coated with 10-nm-thick gold has been observed. The microstructure of the whiskers grown on a Ni substrate by electrochemical deposition has been examined by scanning electron microscope, energy dispersive x-ray spectrometer, x-ray diffraction spectrometer, and Raman spectroscopy. For a 220 μm anode-cathode gap, emission current densities in excess of ∼2×10−6 A/cm2 are observed for applied voltages of 660 V or greater. Although it is believed that the electric field is locally enhanced by the geometry of the whiskers, the voltage required increases roughly linearly with the anode-cathode spacing, corresponding to a turn-on field of approximately 3 V/μm, and an emission current density of 0.4 mA/cm2 has been obtained for an applied field of 5.5 V/μm. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.365714
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  • 7
    Digitale Medien
    Digitale Medien
    Synthesis and electron field emission of nanocrystalline diamond thin films grown from N2/CH4 microwave plasmas (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4546-4550 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Nanocrystalline diamond films have been synthesized by microwave plasma enhanced chemical vapor deposition using N2/CH4 as the reactant gas without additional H2. The nanocrystalline diamond phase has been identified by x-ray diffraction and transmission electron microscopy analyses. High resolution secondary ion mass spectroscopy has been employed to measure incorporated nitrogen concentrations up to 8×1020 atoms/cm3. Electron field emission measurements give an onset field as low as 3.2 V/μm. The effect of the incorporated nitrogen on the field emission characteristics of the nanocrystalline films is discussed. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.366190
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  • 8
    Digitale Medien
    Digitale Medien
    Control of diamond film microstructure by Ar additions to CH4/H2 microwave plasmas (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1981-1989 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The transition from microcrystalline to nanocrystalline diamond films grown from Ar/H2/CH4 microwave plasmas has been investigated. Both the cross-section and plan-view micrographs of scanning electron microscopy reveal that the surface morphology, the grain size, and the growth mechanism of the diamond films depend strongly on the ratio of Ar to H2 in the reactant gases. Microcrystalline grain size and columnar growth have been observed from films produced from Ar/H2/CH4 microwave discharges with low concentrations of Ar in the reactant gases. By contrast, the films grown from Ar/H2/CH4 microwave plasmas with a high concentration of Ar in the reactant gases consist of phase pure nanocrystalline diamond, which has been characterized by transmission electron microscopy, selected area electron diffraction, and electron energy loss spectroscopy. X-ray diffraction and Raman spectroscopy reveal that the width of the diffraction peaks and the Raman bands of the as-grown films depends on the ratio of Ar to H2 in the plasmas and are attributed to the transition from micron to nanometer size crystallites. It has been demonstrated that the microstructure of diamond films deposited from Ar/H2/CH4 plasmas can be controlled by varying the ratio of Ar to H2 in the reactant gas. The transition becomes pronounced at an Ar/H2 volume ratio of 4, and the microcrystalline diamond films are totally transformed to nanocrystalline diamond at an Ar/H2 volume ratio of 9. The transition in microstructure is presumably due to a change in growth mechanism from CH3⋅ in high hydrogen content to C2 as a growth species in low hydrogen content plasmas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.368331
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  • 9
    Digitale Medien
    Digitale Medien
    Synthesis of nanocrystalline diamond thin films from an Ar–CH4 microwave plasma (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 540-543 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Nanocrystalline diamond thin films have been synthesized in an Ar–CH4 microwave discharge, without the addition of molecular hydrogen. X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy characterizations show that the films consist of a pure crystalline diamond phase with very small grain sizes ranging from 3 to 20 nm. Atomic force microscopy analysis demonstrates that the surfaces of the nanocrystalline diamond films remain smooth independent of the film thicknesses. Furthermore, the reactant gas pressure, which strongly affects the concentration of C2 dimer in the Ar–CH4 plasma as well as the growth rate of the films, has been found to be a key parameter for the nanocrystalline diamond thin film depositions. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.366668
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  • 10
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of highly-conducting nitrogen-doped ultrananocrystalline diamond films (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1441-1443 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ultrananocrystalline diamond (UNCD) films with up to 0.2% total nitrogen content were synthesized by a microwave plasma-enhanced chemical-vapor-deposition method using a CH4(1%)/Ar gas mixture and 1%–20% nitrogen gas added. The electrical conductivity of the nitrogen-doped UNCD films increases by five orders of magnitude (up to 143 Ω−1 cm−1) with increasing nitrogen content. Conductivity and Hall measurements made as a function of film temperature down to 4.2 K indicate that these films have the highest n-type conductivity and carrier concentration demonstrated for phase-pure diamond thin films. Grain-boundary conduction is proposed to explain the remarkable transport properties of these films. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1400761
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