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1

Digitale Medien

The interaction of atomic oxygen with thin copper films (1992)

Gibson, B. C. ; Williams, J. R. ; Fromhold, A. T. ; [weitere]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 96 (1992), S. 2318-2323

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: A source of thermal, ground-state atomic oxygen has been used to expose thin copper films at a flux of 1.4×1017 atoms/cm2 s for times up to 50 min for each of five temperatures between 140 and 200 °C. Rutherford backscattering spectroscopy was used to characterize the oxide formed during exposure. The observations are consistent with the oxide phase Cu2O. The time dependence and the temperature dependence of the oxide layer thickness can be described using oxide film growth theory based on rate limitation by diffusion. Within the time and temperature ranges of this study, the growth of the oxide layers is well described by the equation L(T,t)=3.6×108 exp(−1.1/2kBT)t12, where L, T, and t are measured in angstroms, degrees Kelvin, and minutes, respectively. The deduced activation energy is 1.10±0.15 eV, with the attendant oxidation rate being greater than that for the corresponding reaction in molecular oxygen.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.462028

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2

Digitale Medien

The use of porous ceramic cup water samplers to measure solute leaching on chalk soils (1997)

Williams, J. R. ; Lord, E. I.

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 13 (1997), S. 0

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ISSN: 1475-2743

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract. This paper reports results from a four year study to investigate the suitability of porous ceramic cups to measure solute leaching on shallow chalk soils. Measurements were carried out in one field following surface applications of nitrate and bromide tracers and in two fields after only bromide was applied. Soil water samples were collected from porous cups at 30,60 and 90cm depth after every 25 mm of drainage, and soil samples from 0–30, 30–60 and 60–90 cm were collected monthly eachwinter. Soil matric suctions andvolumetric moisture content were measured in one winter. Leaching losses, measured with ceramic cups were compared with those measured by soil analysis. Porous cups installed in chalk at 60 and 90 cm depth were only able to collect samples regularly when soil matric suctions were less than 15 kPa. Water held at such low suctions is likely to move quickly through relatively large fissures in the chalk. The slow rate of equilibration between solute concentrations in water moving in macrofissures and those in water moving through micropores of the chalk matrix, means that porous cups may not provide good estimates of leaching losses if they are installed in chalk rock.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1475-2743.1997.tb00578.x

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3

Digitale Medien

Field and modelling studies to assess the risk to UK groundwater from earth-based stores for livestock manure (2001)

Gooddy, D. C. ; Hughes, A. G. ; Williams, A. T. ; [weitere]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 17 (2001), S. 0

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ISSN: 1475-2743

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract. Boreholes have been constructed at eight sites on the Permo-Triassic Sandstone and Chalk aquifers to assess the extent of chemical and microbiological contamination emanating from unlined farm manure stores. Slurry along fracture faces in the Chalk was found on cores taken from beneath two stores. Porewaters from the Chalk sites and one of the Sandstone sites were discoloured and showed high concentrations of nitrate, ammonium and organic carbon to depths in excess of 10 m. Although Cryptosporidia and Escherichia coli O157 were found in many of the cattle slurry lagoons, neither were found in the aquifer material beneath. The self-sealing of unlined slurry stores is seen as a crucial step in minimizing leakage. A simple mass balance shows farm boreholes near to contaminant sources are at greater risk than public supply wells. Contaminant modelling shows discontinuing use of an unlined farm manure store will lead to little difference in solute concentrations over the short to medium term. Groundwater is most at risk where the water table is shallow since direct hydraulic connection between the lagoon base and the water table considerably increases the rate of vertical migration. This is of greatest significance for pathogens that are thought to be relatively short lived in the subsurface. Under the majority of situations minimal threat is posed to potable groundwater drinking supplies.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1475-2743.2001.tb00018.x

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4

Digitale Medien

High-temperature ohmic contact to n-type 6H-SiC using nickel (1995)

Crofton, J. ; McMullin, P. G. ; Williams, J. R. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 77 (1995), S. 1317-1319

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Specific contact resistances measured at elevated temperatures for Ni ohmic contacts to 6H-SiC were reported. The specific contact resistances were measured with the linear transmission line method at both room temperature and at 500 °C and yielded values 〈5×10−6 Ω cm2 at both temperatures. The trend shows a decreasing contact resistance at higher temperatures. The annealed metal film is a nickel silicide with substantial mixing of C throughout the silicide layer. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.358936

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5

Digitale Medien

Contact resistance measurements on p-type 6H-SiC (1993)

Crofton, J. ; Barnes, P. A. ; Williams, J. R. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 62 (1993), S. 384-386

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Specific contact resistance measurements are reported for Al-Ti ohmic contacts to epitaxial p-type 6H-SiC as a function of epitaxial doping. The circular transmission line method was used to measure the specific contact resistance including the sheet resistance of the epitaxial layer and the modified sheet resistance under the contact. Epitaxial layers with Al doping between 5.5×1015 and 2×1019 cm−3 yielded specific contact resistances between 2.9×10−2 and 1.5×10−5 Ω cm2. A good theoretical fit to the contact resistance data was obtained by assuming the metal-6H-SiC barrier height to equal 0.37 eV.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.108964

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6

Digitale Medien

Effect of nitric oxide annealing on the interface trap densities near the band edges in the 4H polytype of silicon carbide (2000)

Chung, G. Y. ; Tin, C. C. ; Williams, J. R.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 76 (2000), S. 1713-1715

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Results of capacitance–voltage measurements are reported for metal–oxide–semiconductor capacitors fabricated using the 4H polytype of silicon carbide doped with either nitrogen (n) or aluminum (p). Annealing in nitric oxide after a standard oxidation/reoxidation process results in a slight increase in the defect state density in the lower portion of the band gap for p-SiC and a significant decrease in the density of states in the upper half of the gap for n-SiC. Theoretical calculations provide an explanation for these results in terms of N passivating C and C clusters at the oxide–semiconductor interface. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.126167

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7

Digitale Medien

SPNM, A MODEL FOR PREDICTING SEDIMENT, PHOSPHORUS, AND NITROGEN YIELDS FROM AGRICULTURAL BASINS (1980)

Williams, J. R.

Oxford, UK : Blackwell Publishing Ltd

Journal of the American Water Resources Association 16 (1980), S. 0

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ISSN: 1752-1688

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie

Notizen: : A model called SPNM from the words “sediment-phosphorus-nitrogen model” was developed for simulating agricultural contributions to water pollution. SPNM is designed to predict sediment, P, and N yields for individual storms on small basins and to route these yields through streams and valleys of large basins. Users need no computer programming experience because the model is a problem-oriented computer language. SPNM is useful in planning water resources projects and in research. Tests of the model on a watershed provided realistic results.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1752-1688.1980.tb02497.x

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8

Digitale Medien

Phase determination and spatial distribution of an ion-beam mixed internal interface: Fe/Sn (1990)

Sanders, J. H. ; Edwards, D. L. ; Williams, J. R. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 67 (1990), S. 3121-3131

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Ion-beam mixing of tin on iron provides corrosion protection against high-temperature oxidation. Previous studies have been inconclusive as to the exact composition and distribution of alloys produced at the Fe/Sn interface. This study provides a detailed diagram of Fe-Sn specimens after ion-beam mixing with Ar+ at 40 keV and a dose of 5×1016 ions/cm2 . The interface was isotopically labeled with 7.5 nm of 57 Fe and 119 Sn so that dual perspective conversion electron Mössbauer spectroscopy could be performed. Analyses in this manner allowed comparison of 119 Sn conversion electron Mössbauer spectroscopy (CEMS) and 57 Fe CEMS spectra to accurately assign spectral components which could not be conclusively assigned using a single CEMS perspective. Information from Rutherford backscattering spectrometry confirmed the layered nature of specimens prior to implantation and was used for depth determination of the mixed region after implantation. X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and scanning electron microscopy also provided information after implantation. Data indicate the formation of a uniform amorphous surface during implantation resulting in a heterogeneous mixture of components consisting mainly of dilute tin in iron (approximately 8-at. % Sn) and FeSnx (x≈1). About 80% of the 37.5-nm tin overlayer was removed by sputtering. The components identified are somewhat more iron rich than previous assignments and illustrate the difference in surface structures resulting from various implantation parameters.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.345389

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9

Digitale Medien

Capacitance-voltage studies of InP metal-oxide-semiconductor devices irradiated with 4He+ ions (1989)

Tin, C. C. ; Barnes, P. A. ; Williams, J. R. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 66 (1989), S. 4201-4205

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Capacitance-voltage (C-V) measurements have been made on n-InP metal-oxide-semiconductor (MOS) devices damaged by 2-MeV 4 He+ ion bombardment. The C-V curves for samples with thin oxide layer (∼100 A(ring)) show the presence of a depletion layer during both forward and reverse bias. This behavior is significantly different from those of normal, undamaged MOS devices. Measurements made on n-InP MOS samples with different oxide thicknesses show that the C-V curves gradually approach that of a MOS device on a p-type substrate. The anomalous behavior of the C-V curves for the irradiated samples can be explained by the presence of an n-p-n structure under the oxide layer.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.343984

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10

Digitale Medien

FIELD SPRAYS FOR CONTROL OF BEAN AND CABBAGE APHIDS (1963)

Williams, J. R. Parry

Oxford, UK : Blackwell Publishing Ltd

Plant pathology 12 (1963), S. 0

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ISSN: 1365-3059

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1365-3059.1963.tb00225.x

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