scholarly journals Electronic Energy Distribution Function at High Electron Swarm Energies in Neon

1995 ◽  
Vol 48 (3) ◽  
pp. 479
Author(s):  
KL Brown ◽  
J Fletcher
Keyword(s):  
Parallel Plate ◽  
Pressure Range ◽  
Sudden Change ◽  
Electronic Energy ◽  
Vacuum System ◽  
High Electron ◽  
Number Density ◽  
High Energies ◽  
Initial Results ◽  
Electrostatic Analyser

Electron swarms moving through a gas under the influence of an applied electric field have been extensively investigated. Swarms at high energies, as measured by the ratio of the applieq field to the gas number density, E/N, which are predominant in many applications have, in general, been neglected. Discharges at E/N in the range 300 < E/N < 2500 Td have been investigated in neon gas in the pressure range 6 < po < 133 Pa using a differentially pumped vacuum system in which the swarm electrons are extracted from the discharge and energy analysed in both a parallel plate retarded potential analyser and a cylindrical electrostatic analyser. Both pre-breakdown and post-breakdown discharges have been studied. Initial results indicate that as the discharge traverses breakdown no sudden change in the nature of the discharge occurs and that the discharge can be described by both a Monte Carlo simulation and by a Boltzmann treatment given by Phelps et al. (1987).

MOVPE Growth of High Electron Mobility AlGaN/GaN Heterostructures

1995 ◽  
Vol 395 ◽  
Author(s):  
J.M. Redwing ◽  
J.S. Flynn ◽  
M.A. Tischler ◽  
W. Mitchel ◽  
A. Saxler
Keyword(s):  
Electrical Properties ◽  
Electron Gas ◽  
Spatial Separation ◽  
High Electron ◽  
Compositional Dependence ◽  
Dimensional Electron ◽  
Varying Thickness ◽  
Spacer Layer ◽  
Dimensional Electron Gas ◽  
Initial Results

ABSTRACTWe have fabricated AlxGa1−xN/GaN heterostructures with high two-dimensional electron gas (2DEG) mobilities and high sheet carrier densities by metalorganic vapor phase epitaxy (MOVPE). The 2DEG sheet density and mobility exhibit a compositional dependence on the Al fraction of the electron donor layer. The highest mobility (5750 cm2/Vs at 16K) was measured in a sample with x=0.15 that had a sheet carrier density of 8.5×1012 cm−2. The undoped AlxGa1−xN layers have low background carrier concentrations and can be intentionally doped n-type using SiH4. The effect of intentional n-type doping of the AlxGa1−xN donor layer on the electrical properties of the 2DEG was studied in structures that included an undoped AlxGa1−xN spacer layer of varying thickness. Higher 2DEG mobilities were obtained when a 100Å thick undoped layer was included in the structure due to spatial separation of the 2DEG from ionized impurities in the doped AlxGa1−xN. These initial results demonstrate that the electrical properties of AlxGa1−xN/GaN heterostructures can be controlled by intentional doping and appropriate layer design.

Microscopic Analysis of Track Etched Polymeric Membranes

2009 ◽  
Vol 155 ◽  
pp. 107-112 ◽  
Author(s):  
N.K. Acharya
Keyword(s):  
Microscopic Analysis ◽  
Electronic Energy ◽  
Polymeric Membranes ◽  
Energetic Ions ◽  
Force Microscopy ◽  
High Energies ◽  
Atomic Force ◽  
Solution Cast ◽  
Wet Chemical ◽  
Solution Cast Method

The bombardment of energetic ions on polymer membranes will produce the loosely bound passage in the membrane structure due to the energy loss. The Swift Heavy Ions (SHI) creates the latent tracks of several nm surrounded by several tens of nm track halo. The tracks can be visualized under Atomic Force Microscope after wet chemical etching. In present study the polymeric membranes of 30 μm was prepared by solution cast method and irradiated by 60 MeV C+5 energetic ions. The electronic energy losses are predominant at high energies. The membranes were etched chemically to convert the tracks in to suitable pores. The Atomic Force Microscopy (AFM) gives the size and distribution of the pores. The pore size is observed in nano regime. The pore density was found to depend on the irradiation dose.

OPERATION OF AN INVERTED-MAGNETRON GAUGE IN THE PRESSURE RANGE 10−3 TO 10−12 MM. Hg

1958 ◽  
Vol 36 (3) ◽  
pp. 271-288 ◽  
Author(s):  
J. P. Hobson ◽  
P. A. Redhead
Keyword(s):  
Field Emission ◽  
Pressure Range ◽  
Axial Magnetic Field ◽  
Radial Electric Field ◽  
Vacuum System ◽  
Initial Field ◽  
Dynamic Vacuum ◽  
Ionization Gauge ◽  
Field Emission Current ◽  
Positive Ion

A cold-cathode ionization gauge with axial magnetic field and radial electric field is described which is useful in the pressure range 10−3 to 10−12 mm. Hg and has a sensitivity of about 1 amp./mm. Hg. This gauge has the structure of an inverted magnetron with an auxiliary cathode which provides the initial field emission and allows the positive-ion current to be measured independently of the field-emission current. The operation and calibration of the gauge in a dynamic vacuum system is described for the pressure range 10−3 to 5 × 10−9 mm. Hg. Pressures ranging from 10−8 to 10−12 mm. Hg were obtained in sealed-off systems. Liquid-helium trapping was used for pressures below 10−10 mm. Hg. It is shown that the gauge gives a reliable indication of pressure below 10−10 mm. Hg when the pressure is determined by helium diffusion through the envelope.

Epitaxial CeO2 on Silicon Substrates and the Potential of Si/CeO2/Si for SOI Structures

1997 ◽  
Vol 474 ◽  
Author(s):  
A. H. Morshed ◽  
S. X. Liu ◽  
R. Leonard ◽  
F. G. Mcintosh ◽  
N. A. El-Masry ◽  
...  
Keyword(s):  
Optical Properties ◽  
Single Crystal ◽  
High Vacuum ◽  
Silicon On Insulator ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Silicon Substrates ◽  
Cubic Structure ◽  
Lattice Matched ◽  
Initial Results

ABSTRACTCeO2 is nearly lattice matched to Si and has the CaF2 cubic structure thus it offers the potential for the epitaxial growth of an insulating film on Si. Laser ablation of a CeO2 target in an ultra high vacuum system was used for the deposition of single crystal CeO2. The effect of post growth thermal and rapid thermal annealing in O2, N2 and Ar atmosphere was found to have pronounced effects on the electrical properties measured by C-V and the optical properties measured by photoluminescence.We report on our initial results for the growth of epitaxial Si on the deposited CeO2 using low pressure CVD. Both RHEED and TEM studies showed that single crystal epitaxial Si was deposited on CeO2. The details of the Si deposition on CeO2 films for potential of SOI (silicon on insulator) structures will be discussed.

Multiplicity and pseudorapidity distribution in high-energy neutrino-emulsion collisions

1999 ◽  
Vol 77 (1) ◽  
pp. 77-83 ◽  
Author(s):  
F H Liu ◽  
J F Sun
Keyword(s):  
Charged Particles ◽  
High Energy ◽  
Pseudorapidity Distribution ◽  
Number Density ◽  
High Energy Neutrino ◽  
High Energies ◽  
Energy Neutrino ◽  
Pseudorapidity Distributions

The multiplicity and pseudorapidity distributions inneutrino-emulsion collisions at high energies are investigated. Themultiplicity distribution of charged particles, the pseudorapiditydistributions of shower particles, as well as the correlation between amean maximum number density of shower particles and multiplicity, are given.PACS No.: 13.85.Hd

Replication of Wet Objects and Cells

1974 ◽  
Vol 32 ◽  
pp. 102-103
Author(s):  
S. Basu ◽  
D. F. Parsons
Keyword(s):  
Water Vapor Pressure ◽  
High Vacuum ◽  
Polystyrene Latex ◽  
Vacuum System ◽  
Saturated Water Vapor ◽  
Replication Method ◽  
New Methods ◽  
Saturated Water ◽  
Water Vapors ◽  
Intermediate Chamber

We are approaching the invasiveness of cancer cells from the studies of their wet surface morphology which should distinguish them from their normal counterparts. In this report attempts have been made to provide physical basis and background work to a wet replication method with a differentially pumped hydration chamber (Fig. 1) (1,2), to apply this knowledge for obtaining replica of some specimens of known features (e.g. polystyrene latex) and finally to realize more specific problems and to improvize new methods and instrumentation for their rectification. In principle, the evaporant molecules penetrate through a pair of apertures (250, 350μ), through water vapors and is, then, deposited on the specimen. An intermediate chamber between the apertures is pumped independently of the high vacuum system. The size of the apertures is sufficiently small so that full saturated water vapor pressure is maintained near the specimen.

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