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ABSTRACT: To extract quantitative electronic structure information from electron energy-loss near-edge structure typically necessitates the separation of spectra into linearly independent components. For this to be accomplished, certain conditions need to be met concerning the localization of chemical bonding and the linear scaling of fine structure with density of states. The dependence of the processing parameters, such as window widths and positions, of the commonly used ‘two-window intensity-ratio’ method to determine the distribution of π and σ bonding of diamond-like carbon films is investigated. It is shown that, although the selection of the integration windows can lead to very large variations in the resultant bonding fractions, the placement of two small windows centred on the edge structures of interest does permit a robust and reliable estimate of bonding. It is demonstrated that the sp3 variations can be reproducibly monitored with a relative accuracy of about ± 5%, and an absolute concentration given with an accuracy of ± 13% for foils of thickness at least up to twice the inelastic mean free path.
Journal of Microscopy 08/2011; 180(1):22 - 32. · 1.63 Impact Factor
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ABSTRACT: Experiments characterizing both the physics of emission and the performance of Mo tips coated with ultrathin film of AlN were conducted. Ultrathin films of AlN with thicknesses ranging from 7 to 21 nm in 1.5 nm increments were deposited onto Mo tips by magnetron sputtering. In situ field emission measurements were performed after each deposition step. Tip radius, thickness, and morphology of AlN coating were characterized with the transmission electron microscopy. The effect of the thickness of AlN on emission was determined using a Fowler–Nordheim analysis. Various surface treatment effects were studied and measurements of maximum current and emission stability were performed, e.g., maximum current from a single Mo tip with 15 nm of AlN coating was 52 μA. © 2001 American Vacuum Society.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 02/2001; · 1.34 Impact Factor
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M. Park,
A. T. Sowers,
C. Lizzul Rinne,
R. Schlesser,
L. Bergman,
R. J. Nemanich,
Z. Sitar,
J. J. Hren, J. J. Cuomo,
V. V. Zhirnov,
W. B. Choi
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ABSTRACT: Two different types of the nitrogen-doped chemical vapor deposited (CVD) diamond films were synthesized with N <sub> 2 </sub> (nitrogen) and C <sub> 3 </sub> H <sub> 6 </sub> N <sub> 6 </sub> (melamine) as doping sources. The samples were analyzed by scanning electron microscopy, Raman scattering, photoluminescence spectroscopy, and field-emission measurements. More effective substitutional nitrogen doping was achieved with C <sub> 3 </sub> H <sub> 6 </sub> N <sub> 6 </sub> than with N <sub> 2 </sub>. The diamond film doped with N <sub> 2 </sub> contained a significant amount of nondiamond carbon phases. The sample produced with N <sub> 2 </sub> exhibited a lower field emission turn-on field than the sample produced with C <sub> 3 </sub> H <sub> 6 </sub> N <sub> 6 </sub>. It is believed that the presence of the graphitic phases (or amorphous sp<sup>2</sup> carbon) at the grain boundaries of the diamond and/or the nanocrystallinity (or microcrystallinity) of the diamond play a significant role in lowering the turn-on field of the film produced using N <sub> 2 </sub>. It is speculated that substitutional nitrogen doping plays only a minor role in changing the field emission characteristics of CVD diamond films. © 1999 American Vacuum Society.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 04/1999; · 1.34 Impact Factor
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ABSTRACT: Discontinuous diamond films were deposited on silicon by microwave plasma chemical vapor deposition (MPCVD). The diamond films were sharpened by argon ion etching. Field emission turn-on field was drastically lowered after sharpening. Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were used for structural characterization. Possible mechanisms of field emission from the etched field emitter are discussed
Vacuum Microelectronics Conference, 1998. Eleventh International; 08/1998
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ABSTRACT: Many attempts have been made to improve the electron emission characteristics of cold cathode field emitters. Field emitter arrays are very important for the application of flat panel displays. However, there have been some problems associated with metal field emitters including instability and low emission currents. There have been many attempts to solve these problems in order to make field emitter arrays more feasible. Thin films have previously been deposited on nanotips to lower the turn-on voltage and increase the electron emission. A cermet consisting of chromium silicide and silica has been deposited onto Mo and Cu tips to increase the emission current and improve the current stability
Vacuum Microelectronics Conference, 1998. Eleventh International; 08/1998
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ABSTRACT: Nitrogen-doped CVD diamond films with varying substitutional nitrogen content were prepared. Relatively large amounts of substitutional nitrogen were successfully incorporated into the growing diamond without degrading the quality of the diamond when melamine (C <sub>3</sub>H<sub>6</sub>N<sub>6</sub>) was used as a dopant precursor. It was found that substitutional nitrogen doping has a negligible effect on the electron emission properties of the CVD diamond films. Field emission characteristics from diamond powder coated emitters were also investigated. The effect of substitutional nitrogen incorporation on field emission from diamond is discussed
Vacuum Microelectronics Conference, 1998. Eleventh International; 08/1998
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Vacuum Microelectronics Conference, 1997. Technical Digest., 1997 10th International; 09/1997
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Vacuum Microelectronics Conference, 1997. Technical Digest., 1997 10th International; 09/1997
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Vacuum Microelectronics Conference, 1997. Technical Digest., 1997 10th International; 09/1997
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Vacuum Microelectronics Conference, 1997. Technical Digest., 1997 10th International; 09/1997
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Vacuum Microelectronics Conference, 1997. Technical Digest., 1997 10th International; 09/1997
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ABSTRACT: An analysis of wide band gap materials from the point of view of their application in cold emission devices is presented, and criteria of material choice for device application are discussed. Not only material but also technological parameters are taken into consideration. Among the material parameters, the following were found to be the most important; electron affinity, dielectric constant, thermal conductivity, melting point, chemical and physical robustness. The major technological parameter is compatibility of the material deposition process with commercially available facilities and other steps of cathode fabrication. It was shown that wide band gap materials are most effective for emission if deposited on sharp conductive tips. Experimental results from diamond, AlN, c -BN, and SiO <sub> 2 </sub> field emitters are presented and some possible mechanisms explaining their I–V characteristics are discussed. © 1997 American Vacuum Society.
Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 06/1997; · 1.25 Impact Factor
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ABSTRACT: Electron emission from a polycrystalline diamond coated silicon field emitter surface was studied using in situ exposure to various gas species during its operation. Significant enhancement of the electron emission was found after the emitting surface was exposed to hydrogen at pressures in the range 5×10<sup>-4</sup> to 10<sup>-3</sup> Torr. Introducing other gases such as Ne and He only suppressed the emission current. A continuous emission current was measured from such a hydrogen‐exposed surface even after the electric field was reduced to below the initial threshold for electron emission. No similar result was found for pure silicon surface when identical conditions applied. This phenomenon was interpreted as the formation of a dynamically vacuum‐stable layer by polarized hydrogen and the diamond surface. Such a surface layer may significantly lower the surface barrier and exhibit the negative electron affinity property. © 1996 American Institute of Physics.
Applied Physics Letters 01/1997; · 3.84 Impact Factor
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ABSTRACT: The field emission properties of molybdenum and silicon emitter coated with tetrahedral amorphous carbon (or amorphous diamond) were studied. The tetrahedral amorphous carbon was deposited by laser ablation and showed a uniformly coated columnar structure over the entire emitter. In general, current conditioning improved stability and increased the current density. Coatings of ta-C on Mo emitters with and without nitrogen incorporated both yielded significantly higher emissivity than uncoated emitters. Nitrogen incorporation reduced the effective workfunction and the sp3/sp2 ratio. However similar depositions on Si emitters reduced the emissivity, and may be attributable to the residual oxide at the ta-C/Si interface. Annealing in a hydrogen atmosphere enhanced emissivity from both ta-C/Mo and ta-C/Si emitters. In general, thick coatings lowered the emissivity and the slope of the I-V curves. A temperature dependence of emission was observed only in the low field regions.
MRS Proceedings. 12/1996; 498.
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ABSTRACT: The cathodic arc provides a method for depositing extremely hard thin carbon films. These films are potentially useful in a variety of tribological applications including protection of magnetic media and recording heads. Effective application of this technology requires an improved understanding of the influence of process parameters on the microstructure and hardness of the deposited films. In this work, we use a commercially available filtered cathodic arc to deposit tetrahedral amorphous carbon at several deposition angles.
MRS Proceedings. 12/1996; 498.
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ABSTRACT: Hard carbon films can be prepared by the condensation of energetic carbon species at or below room temperature. These amorphous films are primarily tetrahedrally coordinated and contain high fractions of sp3 bonds leading to the terminology amorphous diamond. These films have been successfully doped with phosphorus up to 1 at.%, by other researchers by using a phosphorus doped graphite target. We have also investigated evaporated phosphorus in conjuction with a filtered cathodic arc to incorporate phosphorus into the films and have successfully incorporated phosphorus up to 40 at.% into our films using this technique. XPS showed that some of the phosphorus was clustered. PEELS revealed that with an incorporation of 40 at.% of phosphorus, the sp3 content was approximately 20%.
MRS Proceedings. 12/1996; 498.
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ABSTRACT: Recent studies have shown that thin layers of wide band gap materials such as silicon carbide and diamond can improve electron emission from of sharp field emitters. Aluminum and boron nitrides possess characteristics similar to those of diamond, e.g. chemical and mechanical stability, a wide band gap (from 6-7 eV), a reported negative electron affinity, and the ability to be doped p-type. There is also the possibility of n-type doping. In this study we investigate the field emission properties of these III-V nitrides deposited onto silicon and molybdenum by both reactive magnetron sputtering and by dielectrophoresis. Emission properties for diamond, AlN, and c-BN are compared and are projected to other wide band gap materials
Vacuum Microelectronics Conference, 1996. IVMC'96., 9th International; 08/1996
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ABSTRACT: To improve the performance of molybdenum and silicon field emitters, thin diamond layers were deposited on needles by dielectrophoresis. Field emission characteristics were investigated before and after diamond deposition. SEM and TEM observation demonstrated that a significant amount of diamond was deposited. The emissivity depended upon the thickness deposited, the thermal treatment of the diamond after deposition. The influence of the emitter/diamond interface and the surface treatment of the diamond, are reported here, along with a discussion of the possible mechanisms
Vacuum Microelectronics Conference, 1996. IVMC'96., 9th International; 08/1996
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ABSTRACT: Amorphous carbon was deposited on needle‐shaped Si field emitters by filtered cathodic arc. Electron emission was obtained from these coated cathodes, but was reduced compared to emission from uncoated Si cathodes. Electron energy loss spectroscopy indicated that the coating was a high sp<sup>2</sup> content amorphous carbon. Au particles were found to have precipitated out of the Si emitters, which were grown by a vapor–liquid–solid technique utilizing the Au–Si eutectic during the oxidation and chemical etch sharpening of the emitters. High resolution transmission electron microscopy and selected area electron diffraction confirmed the amorphous nature of the coating and the presence of the Au particles at the Si surface. The field emission, electron energy loss spectroscopy, high resolution transmission electron microscopy, and selected area electron diffraction results are presented and discussed. © 1996 American Vacuum Society
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 06/1996; · 1.34 Impact Factor
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ABSTRACT: Diamond deposition onto single Mo field emitters was accomplished by two methods: microwave plasma chemical vapor deposition and a dielectrophoresis of diamond powder. Observation by transmission electron microscopy and scanning electron microscopy revealed a significant amount of deposition at the tips. The field emission characteristics were measured before and after diamond deposition on the same emitters. Field emission from diamond coated emitters yielded significant increases in emission current and lower Fowler–Nordheim slopes. We discuss a possible mechanism to explain current enhancement that depends primarily upon the Mo‐diamond interface. © 1996 American Vacuum Society
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 06/1996; · 1.34 Impact Factor
