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Artificial diamond is an ideal material for high power, high voltage electronic devices, and for engineering use in extreme environments. Diamond process development requires parallel development in characterization techniques suc...
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Artificial diamond is an ideal material for high power, high voltage electronic devices, and for engineering use in extreme environments. Diamond process development requires parallel development in characterization techniques such as ultra low energy SIMS (uleSIMS), especially in the ability to depth profile for impurities and dopants at high depth resolution.
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We have formed and characterized polycrystalline diamond films with surfaces having hydrogen terminations, oxygen terminations, or fluorine terminations, using a small, simple and novel plasma gun to bombard the diamond surface, f...
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We have formed and characterized polycrystalline diamond films with surfaces having hydrogen terminations, oxygen terminations, or fluorine terminations, using a small, simple and novel plasma gun to bombard the diamond surface, formed by plasma assisted CVD in a prior step, with ions of the wanted terminating species. The potential differences between surface regions with different terminations were measured by Kelvin Force Microscopy (KFM). The highest potential occurred for oxygen termination regions and the lowest for fluorine. The potential difference between regions with oxygen terminations and hydrogen terminations was about 80 mV, and between regions with hydrogen terminations and fluorine terminations about 150mV. Regions with different terminations were identified and imaged using the secondary electron signal provided by scanning electron microscopy (SEM), since this signal presents contrast for surfaces with different electrical properties. The wettability of the surfaces with different terminations was evaluated, measuring contact angles. The sample with oxygen termination was the most hydrophilic, with a contact angle of 75°; hydrogen-terminated regions with 83°, and fluorine regions 93°, the most hydrophobic sample.
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Microparticle bombardment technology has evolved as a method for delivering exogenous nucleic acids into plant cells and is a commonly employed technique in plant science. Desired genetic material is precipitated onto micron-sized...
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Microparticle bombardment technology has evolved as a method for delivering exogenous nucleic acids into plant cells and is a commonly employed technique in plant science. Desired genetic material is precipitated onto micron-sized metal particles and placed within one of a variety of devices designed to accelerate these "microcarriers" to velocities required to penetrate the plant cell wall. In this manner, transgenes can be delivered into the cell's genome or plastome. Since the late 1980s microparticle bombardment has become a powerful tool for the study of gene expression and production of stably transformed tissues and whole transgenic plants for experimental purposes and agricultural applications. This paper reviews development and application of the technology, including the protocols and mechanical systems employed as delivery systems, and the types of plant cells and culture systems employed to generate effective "targets" for receiving the incoming genetic material. Current understanding of how the exogenous DNA becomes integrated into the plant's native genetic background are assessed as are methods for improving the efficiency of this process. Pros and cons of particle bombardment technologies compared to alternative direct gene transfer methods and Agrobacterium based transformation systems are discussed.
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The building up of the space charge induced by electron bombardment in an insulating target is due to the stabilization of self-trapped electrons and holes in polaronic traps. For the energies considered, the target charges positi...
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The building up of the space charge induced by electron bombardment in an insulating target is due to the stabilization of self-trapped electrons and holes in polaronic traps. For the energies considered, the target charges positively and the secondary electrons emitted at low energies can be attracted back to the surface. This results in a self-regulation effect where the total secondary yield tends to unity and the surface potential stabilizes at a low positive value. This conclusion is checked for various experimental conditions. The electrons landing on the target form a ring of negative charges that progressively spread out on the surface of the sample. [References: 21]
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Investigations on the electron plasma parameters and ion energy distributions (IEDs) at the grounded electrode (anode) of an asymmetrical capacitively coupled rf discharge in argon are presented. These are compared with studies fr...
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Investigations on the electron plasma parameters and ion energy distributions (IEDs) at the grounded electrode (anode) of an asymmetrical capacitively coupled rf discharge in argon are presented. These are compared with studies from previous papers related to the sheath formed in front of the powered electrode. The I-V characteristics provided by a self-compensated Langmuir probe show the existence of a bi-Maxwellian distribution with a bulk cold election group and a hot electron group. From mass spectrometric investigations, the IEDs exhibit a double peak shape. The theoretical model for transport of the ions and electrons in the sheath of a capacitively coupled, asymmetric rf discharge was considered. Combination of two effects, the rf modulation of the sheath potential and charge exchange as a dominant inelastic interaction process in the sheath, leads to pronounced and characteristic additional structures in the IEDs. [References: 15]
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Electrical, photoelectric, and magnetic properties of CdS single crystals undoped and doped with copper (N-Cu approximate to 10(18) cm(-3)) and irradiated with electrons (E = 1.2 MeV, Phi = 2 x 10(17) cm(-2)) and neutrons (E = 2 M...
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Electrical, photoelectric, and magnetic properties of CdS single crystals undoped and doped with copper (N-Cu approximate to 10(18) cm(-3)) and irradiated with electrons (E = 1.2 MeV, Phi = 2 x 10(17) cm(-2)) and neutrons (E = 2 MeV, Phi = 10(18) cm(-2)) are studied. It is shown that the donor-acceptor pairs are responsible for extrinsic photoconductivity and paramagnetic properties; in particular, these pairs are represented by Cu-Cd(-) -D+ complexes that are destroyed during irradiation and are formed again with time (as secondary radiation defects) in irradiated samples. It is established that the majority of paramagnetic centers and donor-acceptor pairs are located in the near-surface region of the crystal. It is confirmed that large structural defects (defect clusters) formed by irradiation with neutrons are efficient sinks for copper atoms. Specific features of isochronous annealing of paramagnetic centers and donor-acceptor pairs responsible for the variation in magnetic parameters and in the photoconductivity spectra of irradiated undoped and Cu-doped CdS samples are studied.
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In recent weeks,we have seen the European Parliament's Environment Committee suggesting that the proposed 'F-gas regulation' - designed to restrict the use of fluorine-containing gases - be handled only under the environmental leg...
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In recent weeks,we have seen the European Parliament's Environment Committee suggesting that the proposed 'F-gas regulation' - designed to restrict the use of fluorine-containing gases - be handled only under the environmental legal framework of the Treaty of Rome (Article 175).
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Magnetic properties of [Co(0.4 nm)/Pt(0.7 nm)](5) multilayers are tailored by controlling the sputtering voltage during growth of cobalt layers by a facing target cathode. It is shown that increasing sputtering voltage up to 150 V...
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Magnetic properties of [Co(0.4 nm)/Pt(0.7 nm)](5) multilayers are tailored by controlling the sputtering voltage during growth of cobalt layers by a facing target cathode. It is shown that increasing sputtering voltage up to 150 V leads to an improved crystalline texture and this results in larger magnetic anisotropies together with increased out-of-plane coercive fields. At a higher cathode voltage of 540 V, however, crystalline texture quality slightly worsens and this is accompanied by a decrease in the effective anisotropy. Using facing target cathode sputtering, the crystalline structure of the multilayers can be controlled without applying any heat treatment and this can be utilized to optimize the magnetic properties of Co/Pt multilayers for specific applications. (C) 2021 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc.
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High heat flux experiments using a helium beam have been carried out on powder metallurgy tungsten. The energy of He is 19keV. He beam flux and heat flux at the beam center is 2.0 x 10(21) He/m(2)s and 6.0 MW/m(2), respectively. B...
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High heat flux experiments using a helium beam have been carried out on powder metallurgy tungsten. The energy of He is 19keV. He beam flux and heat flux at the beam center is 2.0 x 10(21) He/m(2)s and 6.0 MW/m(2), respectively. Beam duration is 3.0-3.9s and interval of beam shot start is 30s. The samples are irradiated up to a fluence of 10(22)-10(24) He/m(2) by the repeated irradiation pulses. In addition to the He beam irradiation, high heat flux experiments using hydrogen and electron beams have also been carried out on the samples. After the irradiation, surface modification by the irradiation has been investigated. Surface modification by helium and hydrogen beams is completely different from results of electron beam heating. In particular, helium beam heating causes remarkably surface modification such as a fine-scale rough surface at a peak temperature above 2400degreesC. (C) 2004 Elsevier B.V. All rights reserved.
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The dynamic Monte Carlo computer simulation has been used to estimate the mean sputter depth and the surface composition gradient of binary component materials during prolonged ion bombardment. Calculation results indicate that fo...
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The dynamic Monte Carlo computer simulation has been used to estimate the mean sputter depth and the surface composition gradient of binary component materials during prolonged ion bombardment. Calculation results indicate that for Pt0.5Cu0.5 sputtering, the Pt mean sputter depth is much larger than for Cu at high fluence, but the Pt mean sputter depth approximates Cu at the zero fluence (in the low fluence limit). For B-10(0.2) B-11(0.8) sputtering the B-10 mean sputter depth approximates the B-11 one, not only at the zero fluence but also at high fluence. The calculation results also indicate that the mean sputter depth depends on the surface composition gradient during prolonged ion bombardment. This dependence should be deeply concerned in high fluence sputtering and high fluence implantation areas. [References: 13]
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