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  • 1
    Electronic Resource
    Electronic Resource
    Electrical characteristics of hydrogen implanted silicon Schottky diodes having large difference in metal work function (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5040-5043 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogen ion implantation was carried out on Schottky diodes having large difference in metal work function, Ti/p-Si and PtSi/p-Si diodes. Current-voltage (I-V) measurements showed that, following ion implantation, Ti/p-Si diodes exhibited rectifying characteristics; in contrast, no significant rectifying behavior was observed in the PtSi/p-Si diodes. These results showed a dependence of the implantation effects upon metal overlayer work functions. Consequently, the observations did not seem to indicate the occurrence of Fermi level pinning due to a highly damaged near-surface region after ion implantation, as previously suggested. Capacitance-voltage (C-V) measurements revealed a decrease in the diode capacitances along with a significant reduction of acceptor concentration following the implantation. In general, the results suggest that ion implantation alters the electrical characteristic of the diodes mainly by creating defects in the semiconductor depletion region. All such defects act as recombination centers giving rise to a deviation of the electrical characteristics from the normal behavior. They do not play a role in producing a Fermi level pinning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340400
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of phosphorus liquid-metal ion source as a dopant source in focused ion beam systems (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 603-610 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Characteristics of a phosphorus liquid-metal ion source (LMIS) for use in focused ion beam systems was investigated because of its potential as an n-type dopant for integrated circuit device fabrication. A continuous lifetime of more than 33 h was recorded as a part of the source stability measurement. Short-term stability measurements indicated a very stable beam emission during its operation. Three different emitter tip radii of 2.5, 5.0, and 10 μm were selected to examine phosphorus beam emission characteristics. Mass spectrum measurements were used to examine phosphorus ion content and beam stability by repeat scanning. Steep current-voltage characteristics were observed for 5.0- and 10-μm emitter tip radii. The beam purity was characterized with Auger electron spectroscopy and a scanning electron microprobe by analysis of the deposited beam on a flat silicon substrate. Microstructure analysis by optical metallography indicated no liquid-metal corrosion on the emitter tip. A thorough analysis was carried out on beam purity and metallurgical aspects of LMIS in order to develop a more reliable phosphorus liquid-metal ion source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340099
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  • 3
    Electronic Resource
    Electronic Resource
    Characteristics and surface analysis of ion beam deposition from binary boron platinum (Pt58B42) liquid-metal ion source (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 878-886 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Characteristics of a eutectic boron platinum (Pt58B42) liquid-metal ion source (LMIS) were analyzed and investigated with a quadrupole mass spectrometer (QMS), Auger electron spectroscopy (AES), and Rutherford backscattering spectroscopy (RBS). The source characteristics can be explained by the hydrodynamic model, particularly for needle geometry LMIS. Surface analysis with RBS and AES indicated that more boron is produced in the ion beam than left in the liquid alloy reservoir and more droplets are produced with a 10-μm emitter tip radius, which reduced boron current in the beam. The source instability was associated with droplet formation. AES results show that substantial neutral ions were produced which was not detected by QMS. RBS results on the depleted residual alloy remaining on the carbon ribbon heater indicated that the cause of the alloy system's short lifetime (33 h) is due to a change in alloy stoichiometry to a higher platinum content. Three different emitter tip radii (2.5, 5, and 10 μm) made of graphite were used in the present investigation. Higher boron current and high stability during ion emission was recorded with 2.5-μm graphite emitter tip radius than with the 5- or 10-μm tip radii.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340029
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  • 4
    Electronic Resource
    Electronic Resource
    High current Cu3P liquid metal ion source using a novel extractor configuration (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 2170-2172 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It has been found that by utilizing a sharp needle for the extractor electrode in close proximity to the source tip wetted with Cu3P liquid alloy, a large increase (factor ∼300) in ion current is observed in comparison to standard liquid metal ion sources (LMIS's). In standard previously used LMIS's the extractor electrode was a flat plane with a circular hole centered on the source needle tip. This new high current source has important applications in focused and broad ion beam deposition systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98931
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  • 5
    Electronic Resource
    Electronic Resource
    Radiation-induced molecular changes inEscherichia coli B and its S-30 and DNA-plus-membrane fractions (1983)
    Springer
    Journal of biological physics 11 (1983), S. 69-74 
    Details
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Oxygenated aqueous suspensions ofEscherichia coli B cells in the resting state were irradiated with 0.8-MeV electrons. Dried films of whole cells, the S-30 fraction, and the DNA-plus-membrane fraction were studied by using infrared spectroscopy in conjunction with the technique of attenuated total reflectance (ATR) in the range from 4000 cm−1 to 800 cm−1. Cells irradiated in the oxygenated or the anoxic state yield the same kind of molecular damage, the main difference being the lower doses (by a factor 4 or 5) required in well oxygenated systems. Results show that some bonds are more sensitive to radiation than others. Decreases in the PO2 bands (1225 and 1084 cm−1) indicate radiation-induced degradation of the DNA-RNA backbone. The increase in absorption between 1700 cm−1 and 1750 cm−1 indicates formation of C=O bonds upon exposure to ionizing radiation. Most of the radiation damage occurs in cells that have undergone lysis during irradiation, but the process of cell lysis, by itself, does not cause appreciable molecular bond damage as measured by ATR. Doses ranged from 0.1 Mrad to 1.1. Mrad.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01873185
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  • 6
    Electronic Resource
    Electronic Resource
    An infrared spectroscopy study of the molecular structure changes of DNA after electron and ultraviolet irradiation (1975)
    Springer
    Journal of biological physics 3 (1975), S. 155-171 
    Details
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Samples of calf thymus DNA and two different leukemic leukocyte DNA's in the solid state have been irradiated (at 300°K) with 800 keV electrons and 4.9 eV (2537Å) ultraviolet rays. The subsequent effects on the DNA's have been studied using infrared spectroscopy as the probe for radiation-produced molecular alterations. The region of the infrared spectrum studied covered the wave number range from 4000 cm−1 to 300 cm−1. Our results indicate that under electron and ultraviolet irradiation, the prominent infrared active absorption peaks of all three DNA's are altered. The infrared results of our ultraviolet irradiation of DNA indicate that similar molecular bonds are broken as for the case of DNA irradiated with 800 keV electrons. The results indicate that up to high doses, calf thymus DNA is more sensitive to electron irradiation than the leukemic leukocyte DNA's. The infrared active absorption peaks of the two leukemic leukocyte DNA's respond similarly to electrons. The ultraviolet results indicate some difference between calf thymus DNA and the two leukocyte DNA's in their response to 4.9 eV light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02309002
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  • 7
    Electronic Resource
    Electronic Resource
    Flow properties of various irradiated resins of PTFE (teflon)Based on the Ph.D. thesis of W. Keith Fisher at Rensselaer Polytechnic Institute, May 1981. (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3769-3786 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Changes in the melt viscosity of PTFE exposed to various radiation doses in air were measured using a capillary rheometer. The melt viscosity decreases dramatically after exposure to 2.5 MRad, but between 2.5 and 5 MRad there is an increase in viscosity which is attributed to the formation of branches and crosslinks. Above 5 MRad, the melt viscosity decreases with dose. Plots of log apparent melt viscosity vs. log apparent shear rate are given for PTFE exposed to various radiation doses. The data in each of these plots can be fit by a straight line (power law), and changes in the slopes of these lines are interpreted to indicate changes in the molecular weight distribution. It is postulated that the observed decrease in the slopes of these lines after irradiation is caused by a narrowing of the molecular weight distribution because of the decrease in the number of molecules at the high molecular weight end of the distribution. The melt viscosity of a PTFE sample irradiated to a given dose was less for a sample of low preirradiation crystallinity than for an otherwise identical sample of higher crystallinity. This crystallinity dependence of viscosity is related to differences in oxygen diffusion properties of crystalline and amorphous PTFE.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1982.070271013
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of ionizing radiation on the chemical composition, crystalline content and structure, and flow properties of polytetrafluoroethylene (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2465-2493 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article describes a study of ionizing radiation-induced changes in the chemical composition, crystalline content and structure, and flow properties in polytetrafluoroethylene (PTFE). Irradiatins conducted in the presence of oxygen cause acid fluoride end groups to be formed, which on exposure to water vapor hydrolyze to form carboxylic acid end groups. Analyses by infrared (IR) spectroscopy indicate that when irradiated in a vacuum PTFE exhibits defect absorption bands which have been attributed to branch and crosslink formation. The crystalline content of PTFE which increases after exposure to radiation was monitored by IR spectroscopy, density, x-ray diffraction on unoriented samples, and differential scanning calorimetry (DSC) as the measurement probes. The melt viscosity of PTFE exposed to various radiation doses in air decreases dramatically after irradiation. Between 2.5 and 5 Mrd an increase in viscosity is attributed to the formation of branches and crosslinks. The effects of preirradiation crystallinity and postirradiation heat treatment were studied. A model is presented to explain the mechanism of the observed radiation effects.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170191010
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