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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3389-3393 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple and economical microwave plasma-assisted chemical vapor deposition facility has been developed and used for synthesis of diamond thin films. The system is similar to those developed by others but includes several unique features that make it particularly economical and safe, yet capable of producing high quality diamond films. A 2.45-GHz magnetron from a commercial microwave oven is used as the microwave power source. A conventional mixture of 0.2% methane in hydrogen is ionized in a bell jar reaction chamber located within a simple microwave cavity. By using a small hydrogen reservoir adjacent to the gas supply, an empty hydrogen tank can be replaced without interrupting film synthesis or causing any drift in plasma characteristics. Hence films can be deposited continuously for arbitrarily long periods while storing only a 24-h supply of explosive gases. System interlocks provide safe start-up and shut-down and allow unsupervised operation. Here we describe the electrical, microwave, and mechanical aspects of the system, and summarize the performance of the facility as used to reproducibly synthesize high quality diamond thin films.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2386-2388 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the growth of high-quality diamond using a microwave plasma chemical vapor deposition (CVD) system in which the feed gas contains no hydrocarbons, but instead the source of carbon is a graphite piece which resides within the plasma volume. Results of experiments using this technique by itself and in combination with the normal methane feed gas method are described. The samples were analyzed by Raman spectroscopy and scanning electron microscopy. Diamond grown in this way was found to be particularly pure and of high crystallinity.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2015-02-03
    Description: Nanoprobe tips are key components in many applications such as scanning probe microscopes, nanoscale imaging, nanofabrication and sensing. This paper describes a dynamic chemical etching method for the fabrication of optical nanoprobes. The tips are produced by mechanically rotating and dipping a silica optical fibre in a chemical etching solution (aqueous hydrofluoric acid) covered with a protection layer. Using different dynamic regimes of the mechanical movements during the chemical etching process, it is possible to vary the cone angle, the shape, and the roughness of the nanoprobes. It is found that the tip profiles are determined by the nonlinear dynamic evolution of the meniscus of the etchant near the fibre. Computational fluid dynamic simulations have been performed, showing that different flow regimes correspond to different shear forces acting on the forming nanotip, in agreement with experimental results. With this method, a high yield of reproducible nanotips can be obtained, thus overcoming the drawbacks of conventional etching techniques. Typical tip features are short taper length (∼200  μ m), large cone angle (up to 40°), and small probe tip dimension (less than 30 nm).
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 4
    Publication Date: 2014-10-29
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 5
    Publication Date: 2015-03-25
    Description: We study the dependence of the electrical conductivity on the gold concentration of Au-implanted polymethylmethacrylate (PMMA) and alumina nanocomposite thin films. For Au contents larger than a critical concentration, the conductivity of Au-PMMA and Au-alumina is well described by percolation in two dimensions, indicating that the critical correlation length for percolation is larger than the thickness of the films. Below the critical loading, the conductivity is dominated by tunneling processes between isolated Au particles dispersed in PMMA or alumina continuous matrices. Using an effective medium analysis of the tunneling conductivity, we show that Au-PMMA behaves as a tunneling system in two dimensions, as the film thickness is comparable to the mean Au particle size. On the contrary, the conductivity of Au-alumina films is best described by tunneling in three dimensions, although the film thickness is only a few times larger than the particle size. We interpret the enhancement of the effective dimensionality of Au-alumina films in the tunneling regime as due to the larger film thickness as compared to the mean interparticle distances.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 6
    Publication Date: 2014-11-14
    Description: Composites of titanium nanoparticles in alumina were formed by ion implantation of titanium into alumina, and the surface electrical conductivity measured in situ as the implantation proceeded, thus generating curves of sheet conductivity as a function of dose. The implanted titanium self-conglomerates into nanoparticles, and the spatial dimensions of the buried nanocomposite layer can thus be estimated from the implantation depth profile. Rutherford backscattering spectrometry was performed to measure the implantation depth profile, and was in good agreement with the calculated profile. Transmission electron microscopy of the titanium-implanted alumina was used for direct visualization of the nanoparticles formed. The measured conductivity of the buried layer is explained by percolation theory. We determine that the saturation dose, φ 0 , the maximum implantation dose for which the nanocomposite material still remains a composite, is φ 0  = 2.2 × 10 16  cm −2 , and the corresponding saturation conductivity is σ 0  = 480 S/m. The percolation dose φ c , below which the nanocomposite still has basically the conductivity of the alumina matrix, was found to be φ c  = 0.84 × 10 16  cm −2 . The experimental results are discussed and compared with a percolation theory model.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 7
    Publication Date: 2014-08-07
    Description: We report on an experimental study of an ion source based on a Penning discharge with a cold hollow cathode in crossed electric and magnetic fields. The minimum vacuum chamber operating pressure was 3 × 10 −5 Torr for argon and 5 × 10 −5 Torr for hydrogen. The use of a hollow cathode allowed decreasing the discharge operating voltage down to 350 V at a discharge current of ∼100 mA. At a discharge current of 100 mA and beam accelerating voltage of 2 kV, the ion current was 2.5 mA for argon and 8 mA for hydrogen, and the ion beam on-axis current density 170 and 450 μA/cm 2 , respectively. The current-voltage characteristics of the discharge and the radial ion beam current density distribution were measured. The influence of pressure on the discharge parameters and their time stability was investigated.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 8
    Publication Date: 2016-04-13
    Description: Wrinkling of stiff thin films deposited on compliant substrates is an effect that has been broadly investigated. However, wrinkling consequent to metal ion implantation has been less studied. In the work described here, we have explored the sub-micron wrinkling phenomena that spontaneously occur when metal ions (Au and Cr) are implanted with energy of a few tens of electron volts (49 eV for Au and 72 eV for Cr) into a compliant material (PDMS). This very low energy ion implantation was performed using a Filtered Cathodic Vacuum Arc technique, a process often referred to as energetic deposition or energetic condensation. For comparison, Au and Cr depositions with similar doses were also done using a sputtering technique (with lower particle energy of approximately 2 eV), and no wrinkle formation was then observed. In this way, we can discuss the role of ion energy in wrinkle formation. Depth profiles of the implanted material were calculated using the Tridyn computer simulation code for each metal, for several implantation doses. UV-vis absorption spectroscopy analysis confirmed the presence of metal nanoparticles. Atomic Force Microscopy imaging with spectral processing was used to compare the wrinkle morphology for each case investigated.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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