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  • 1
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    Fabrication of an electron multiplier utilizing diamond films (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: High secondary electron yields (sigma=14-27) from polycrystalline diamond films on Mo substrates have been reported previously. We observed that continuous exposure to an electron beam degraded the secondary yield in vacuum as a function of fluence owing to a loss of surface hydrogen. However, the hydrogen partial pressure could be adjusted such that the high secondary yield remained stable during beam exposure. We have constructed a prototype electron multiplier using these diamond films for use in ultrahigh vacuum. A gain of 0.9 times 10(exp 5) has been measured in a d.c. mode. Palladium, titanium and aluminum nitride have been studied for possible dynode substrate materials which might eliminate the need for hydrogen during operation. Total secondary yields as high as 50 were measured from diamond on palladium and sigma was stable at 25 during heating at 700 K in vacuum. Raman spectroscopy and scanning electron microscopy showed that variations in sigma from diamond films on Pd were due to differing concentrations of non-diamond carbon.
    Keywords: SOLID-STATE PHYSICS
    Type: Thin Solid Films (ISSN 0040-6090); 253; 1-2; p. 151-156
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  • 2
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    GaAs MESFET with lateral non-uniform doping (1983)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An analytical model of the GaAs MESFET with arbitrary non-uniform doping is presented. Numerical results for linear lateral doping profile are given as a special case. Theoretical considerations predict that better device linearity and improved F(T) can be obtained by using linear lateral doping when doping density increases from source to drain.
    Keywords: SOLID-STATE PHYSICS
    Type: Commun. and Logic Systems at Millimeter Wave Freq.; 24 p
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  • 3
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    Leakage effects in n-GaAs MESFET with n-GaAs buffer layer (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Whereas improvement of the interface between the active layer and the buffer layer has been demonstrated, the leakage effects can be important if the buffer layer resistivity is not sufficiently high and/or the buffer layer thickness is not sufficiently small. It was found that two buffer leakage currents exist from the channel under the gate to the source and from drain to the channel in addition to the buffer leakage resistance between drain and source. It is shown that for a 1 micron gate-length n-GaAs MESFET, if the buffer layer resistivity is 12 OHM-CM and the buffer layer thickness h is 2 microns, the performance of the device degrades drastically. It is suggested that h should be below 2 microns.
    Keywords: SOLID-STATE PHYSICS
    Type: Commun. and Logic Systems at Millimeter Wave Freq.; 32 p
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  • 4
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    Velocity overshoot of electrons in GaAs with space charge and non-uniform field (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: SOLID-STATE PHYSICS
    Type: - Applied Research (ISSN 0031-8965); 75; 67-72
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  • 5
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    Effect of Ion Sputtering on the Interface Chemistry and Electrical Properties of Au/n-gaas (100) Schottky Contacts (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: Interface sputter damage effects were measured for Sn-doped (approximately 2x10 to the 17th power/cu cm) 100 oriented GaAs. The sputter surfaces were characterized by Auger and X-ray photoelectron spectroscopy. Gold contacts were then deposited in situ on these characterized surfaces. Results of I-V and C-V measurements are shown in graphs.
    Keywords: SOLID-STATE PHYSICS
    Type: Ohmic Contacts, Irradiation Effects, and Thin Film Growth of GaAs and Al sub 1-x Ga sub x As; 8 p
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  • 6
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    Effect of Ion Sputtering on Interface Chemistry and Electrical Properties of an Gaas (100) Schottky Contacts (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Auger and electron photoelectron spectroscopy were used to measure the extent of As depletion during 1 keV to 5 keV argon sputtering of GaAs surfaces. This depletion was correlated with a general decrease in the barrier height of the rectifying Au contact deposited in situ. However, nondestructive angle resolved XPS measurements showed As was depleted at the outer surface more by 1 keV than 3 keV argon. These effects are explained based on a combined work effective work function model and creation of a donor like surface damage layer. The donor layer was correlated with As depletion by sputtering. Deep level trap formation and annealing of sputtering effects were studied.
    Keywords: SOLID-STATE PHYSICS
    Type: Ohmic Contacts, Irradiation Effects, and Thin Film Growth of GaAs and Al sub 1-x Ga sub x As; 30 p
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  • 7
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    Ohmic Versus Rectifying Contacts of Au to N-gaas by Ion Sputtering (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Results of investigations of argon ion sputtering of heavily doped n-GaAs are compared with those obtained from studies of Au/low doping density n-GaAs contacts. The Au contact on Si-doped GaAs was nearly ohmic when the surface contamination (carbon and oxides) was reduced prior to deposition by chemical cleaning. However, when ion sputtering was used in situ to clean the surface, rectifying contact was produced whose barrier height varied with the energy of the sputtering ion. It was found that ion sputtering of GaAs doped to more than 3 x 10 to the 18th power/cu may be used to change ohmic contact to rectifying contacts. The barrier height may be changed by changing the ion energy. The behavior results from the sputter creation of deep level acceptor states at the GaAs surface. Annealing after sputtering can restore the contact to nearly an ohmic character.
    Keywords: SOLID-STATE PHYSICS
    Type: Ohmic Contacts, Irradiation Effects, and Thin Film Growth of GaAs and Al sub 1-x Ga sub x As; 10 p
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  • 8
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    Effect of ion sputtering on interface chemistry and electrical properties of Au GaAs(100) Schottky contacts (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effects of sputtering n-type (100)GaAs with 1 to 5 keV argon ions have been studied in ultrahigh vacuum. Auger electron and X-ray photoelectron spectroscopies have been used to characterize the surface before and after sputtering. Gold Schottky contacts were prepared in situ to avoid contamination at the metal/semiconductor interface. The data show that sputtering depletes the surface in As, and the extent of depletion increased as the ion energy was increased. However, angular-resolved photoelectron data showed As was enriched on the outer atom layer by 5 keV but depleted by 1 keV Ar(+) sputtering. Current and capacitance versus voltage data showed that sputtering always lowered the Schottky barrier height and generally increased the ideality factor. However, the barrier height after 3 keV sputtering was higher than after 1 keV sputtering. Those effects are explained based on a combined effective work function model and creation of a donorlike surface damage layer. The donor layer was correlated with As depletion by sputtering. Deep level trap formation and annealing of sputtering effects were studied.
    Keywords: SOLID-STATE PHYSICS
    Type: Journal of Vacuum Science and Technology B (ISSN 0734-211X); 2; 613-619
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  • 9
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    Superconductivity above 90 K in the square-planar compound system ABa2Cu3O(6 + x) with A = Y, La, Nd, Sm, Eu, Gd, Ho, Er, and Lu (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Superconductivity has been found in the 90-K range in ABa2Cu3O(6 + x) with A = La, Nd, Sm, Eu, Gd, Ho, Er, and Lu in addition to Y. The results suggest that the unique square-planar Cu atoms, each surrounded by four or six oxygen atoms, are crucial to the superconductivity of oxides in general. In particular, the high Tc of ABa2Cu3O(6 + x) is attributed mainly to the quasi-two-dimensional assembly of the CuO2-Ba-CuO(2 + x)Ba-CuO2 layers sandwiched between two A layers, with particular emphasis in the CuO(2 + x) layers. Higher-Tc oxides are predicted for compounds with bigger assemblies of CuO2 layers coupled by Ba layers.
    Keywords: SOLID-STATE PHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 58; 1891-189
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  • 10
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    High-pressure study of the new Y-Ba-Cu-O superconducting compound system (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Hydrostatic effects on the superconducting transition temperature of the Y-Ba-Cu-O compound system, resistively, up to 19 kbar are investigated. It is found that pressure has little effect on the superconducting state of Y-Ba-Cu-O, in marked contrast to the behavior of the K2NiF4-phase La-Ba-Cu-O and La-Sr-Cu-O systems. It is suggested that this effect may be due to chemical pressure associated with the smaller Y atoms already present in Y-Ba-Cu-O. X-ray powder-diffraction studies show that the high-temperature superconductivity in Y-Ba-Cu-O can only be attributed to one or more phases with structures different from the cubic perovskite or tetragonal layered ones.
    Keywords: SOLID-STATE PHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 58; 911
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