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Full-Text Articles in Physics
A Handheld Neutron-Detection Sensor System Utilizing A New Class Of Boron Carbide Diode, Kevin Osberg, Nathan Schemm, M. Susan Hallbeck, Sina Balkir, Peter A. Dowben, Jennifer I. Brand, Michael W. Hoffman
A Handheld Neutron-Detection Sensor System Utilizing A New Class Of Boron Carbide Diode, Kevin Osberg, Nathan Schemm, M. Susan Hallbeck, Sina Balkir, Peter A. Dowben, Jennifer I. Brand, Michael W. Hoffman
Peter Dowben Publications
A handheld neutron-detection sensor application is described in this paper. The sensor system utilizes a new class of boron carbide diode that interacts with incoming neutrons. To interface with the boron carbide diode, an integrated front end is designed in a 1.5-μm standard CMOS technology. With the diode and front-end microchip, a handheld neutron-detection system was realized with an embedded microcontroller for real-time processing. The handheld detector operation was then tested with a plutonium–beryllium neutron source. Test and measurement results confirm the validity of the approach and the functionality of the design.
The All Boron Carbide Diode Neutron Detector: Comparison With Theory, A. N. Caruso, Peter A. Dowben, S. Balkir, Nathan Schemm, Kevin Osberg, R.W. Fairchild, Oscar Barrios Flores, Snjezana Balaz, A.D. Harken, Brian W. Robertson, Jennifer I. Brand
The All Boron Carbide Diode Neutron Detector: Comparison With Theory, A. N. Caruso, Peter A. Dowben, S. Balkir, Nathan Schemm, Kevin Osberg, R.W. Fairchild, Oscar Barrios Flores, Snjezana Balaz, A.D. Harken, Brian W. Robertson, Jennifer I. Brand
Peter Dowben Publications
A boron carbide diode detector, fabricated from two different polytypes of semiconducting boron carbide, will detect neutrons in reasonable agreement with theory. Small deviations from the model calculations occur due to the detection efficiencies of the 10B capture products Li plus α sum signal differing somewhat from expectation in the thin diodes. The performance of the all boron carbide neutron detector does depart from the behavior of devices where a boron rich neutron capture layer is distinct from the diode charge collection region (i.e. a conversion layer solid state detector), as is expected.
Electronic Structure And Polymerization Of A Self-Assembled Monolayer With Multiple Arene Rings, D.Q. Feng, David Wisbey, Yaroslav B. Losovyj, Y. Tai, M. Zharnikov, Peter A. Dowben
Electronic Structure And Polymerization Of A Self-Assembled Monolayer With Multiple Arene Rings, D.Q. Feng, David Wisbey, Yaroslav B. Losovyj, Y. Tai, M. Zharnikov, Peter A. Dowben
Peter Dowben Publications
We find evidence of intermolecular interactions for a self-assembled monolayer (SAM) formed from a large molecular adsorbate, [1,1′;4′,1′′-terphenyl]-4,4′′-dimethanethiol, from the dispersion of the molecular orbitals with changing wave vector k. With the formation self-assembled molecular (SAM) layer, the molecular orbitals hybridize to electronic bands, with indications of significant band dispersion of the unoccupied molecular orbitals. The electronic structure is also seen to be dependent upon temperature, and cross linking between the neighbor molecules, indicating that the electronic structure may be subtly altered by changes in molecular conformation and packing.
Surface Segregation In Multicomponent Clusters, Peter A. Dowben, Ning Wu, Natalie Palina, R. Müller, J. Hormes, Yaroslav B. Losovyj
Surface Segregation In Multicomponent Clusters, Peter A. Dowben, Ning Wu, Natalie Palina, R. Müller, J. Hormes, Yaroslav B. Losovyj
Peter Dowben Publications
Nanostructured materials are not immune from surface segregation, as can be shown for solid samples made from nanosized BaFe12–2xCoxTixO19 barium ferrite particles and a variety of free clusters. Both theory and experiment provide ample demonstration that very limited dimensions of very small clusters does not necessarily impart stability against surface and grain boundary segregation. In fact, with the larger surface to volume ratio in small clusters and lower average atomic coordination, we anticipate that compositional instabilities in small clusters will readily occur.
A Hand-Held Neutron Detection Sensor Systems, K. Osberg, N. Schemm, S. Balkir, Jennifer I. Brand, M. Susan Hallbeck, Peter A. Dowben
A Hand-Held Neutron Detection Sensor Systems, K. Osberg, N. Schemm, S. Balkir, Jennifer I. Brand, M. Susan Hallbeck, Peter A. Dowben
Peter Dowben Publications
In this paper, a hand-held neutron radiation sensor application is described. The sensor system utilizes a new class of boron-carbide diode that interacts with incoming neutrons. To interface with the boron-carbide diode an integrated front-end is designed in a 1.5/spl mu/m standard CMOS technology. With the diode and front-end microchip, a hand-held neutron detection system was realized with an embedded microcontroller for realtime processing. The hand-held detector operation was then tested with a plutonium-beryllium neutron source. Testing results confirm the validity of the approach and the functionality of the design.
Cobaltocene Adsorption And Dissociation On Cu(1 1 1), Jaewu Choi, Peter A. Dowben
Cobaltocene Adsorption And Dissociation On Cu(1 1 1), Jaewu Choi, Peter A. Dowben
Peter Dowben Publications
Photoemission results indicate that the initial adsorption of cobaltocene on Cu(1 1 1) at 150 K leads to molecular fragmentation, but with subsequent cobaltocene exposures, molecular absorption occurs. The molecularly adsorbed species is either adsorbed with only a fraction of molecules adopting a preferential orientation along the surface normal or adsorbed with the molecular axis away from the surface normal. This adsorption behavior is compared to nickelocene and ferrocene adsorption.
Polyvinylidene Fluoride–Trifluoroethylene As A Reservoir For Absorbed Water, P.A. Jacobson, Luis G. Rosa, Kristin Kraemer, Stephen Ducharme, Peter A. Dowben
Polyvinylidene Fluoride–Trifluoroethylene As A Reservoir For Absorbed Water, P.A. Jacobson, Luis G. Rosa, Kristin Kraemer, Stephen Ducharme, Peter A. Dowben
Peter Dowben Publications
The absorption of water in Langmuir–Blodgett films of ferroelectric copolymers of polyvinylidene fluoride with trifluoroethylene is shown to depend upon the film thickness. This water absorption can have a profound effect on the dielectric properties of the copolymer films.
The Interface Electronic Structure Of Thiol Terminated Molecules On Cobalt And Gold Surfaces, A. N. Caruso, Ligen Wang, Sitaram Jaswal, Evgeny Y. Tsymbal, Peter A. Dowben
The Interface Electronic Structure Of Thiol Terminated Molecules On Cobalt And Gold Surfaces, A. N. Caruso, Ligen Wang, Sitaram Jaswal, Evgeny Y. Tsymbal, Peter A. Dowben
Peter Dowben Publications
The bonding strength and interfacial electronic properties of biphenyldimethyldithiol (HS– CH2–C6H4–C6H4–CH2–SH) adsorbed on Au(111) and polycrystalline cobalt are identified from combined photoemission and inverse photoemission. In order to develop a better understanding of the thiol functional group to metal surface interaction, the stable orientation, bonding site, bonding strength and interfacial electronic properties of methylthiol (S–CH3) adsorbed on Au(111) and Co(0001) have been determined by ab initio density functional calculations. Both experiment and theory suggest that thiol bonding to cobalt surfaces is stronger compared to gold surfaces. …
The Electronic Structure Of 1,2-Pcb10H11 Molecular Films: A Precursor To A Novel Semiconductor, Snjezana Balaz, D.I. Dimov, N.M. Boag, K. Nelson, B. Montag, Jennifer I. Brand, Peter A. Dowben
The Electronic Structure Of 1,2-Pcb10H11 Molecular Films: A Precursor To A Novel Semiconductor, Snjezana Balaz, D.I. Dimov, N.M. Boag, K. Nelson, B. Montag, Jennifer I. Brand, Peter A. Dowben
Peter Dowben Publications
The band gaps and electronic structure of un doped films of molecular icosahedra of closo-1-phospha-2 carbadodecaborane (1,2-PCB10H11) are reported. 1,2-PCB10H11 adsorbs on Au and Ag substrates to generate molecular thin films with the Fermi level(chemical potential) placed closer to the lowest unoccupied molecular orbital than has been observed with closo-1,2-dicarbadodecaborane (1,2-C2B10H12, orthocarborane) adsorbed on Co, Cu or Ag. Both 1,2-PCB10H11 and 1,2-C2B10H12 molecular films exhibit an unoccupied molecular defect state above the Fermi level. The vibrational modes, observed in …
Erratum: Strain Induced Half-Metal To Semiconductor Transition In Gdn, Chun-Gang Duan, R.F. Sabiryanov, Jianjun Liu, Wai-Ning Mei, Peter A. Dowben, J.R. Hardy
Erratum: Strain Induced Half-Metal To Semiconductor Transition In Gdn, Chun-Gang Duan, R.F. Sabiryanov, Jianjun Liu, Wai-Ning Mei, Peter A. Dowben, J.R. Hardy
Peter Dowben Publications
The minus sign of the Heisenberg Hamiltonian on p. 3 should be removed since in this Letter we use the negative value to represent ferromagnetic interaction.
Magnetic Ordering In Gd Monopnictides: Indirect Exchange Versus Superexchange Interaction, Chun-Gang Duan, Renat F. Sabiryanov, Wai-Ning Mei, Peter A. Dowben, Sitaram Jaswal, Evgeny Y. Tsymbal
Magnetic Ordering In Gd Monopnictides: Indirect Exchange Versus Superexchange Interaction, Chun-Gang Duan, Renat F. Sabiryanov, Wai-Ning Mei, Peter A. Dowben, Sitaram Jaswal, Evgeny Y. Tsymbal
Peter Dowben Publications
The exchange interaction parameters of Gd monopnictides are deduced from fitting the total energies of different magnetic configurations to those computed within the Heisenberg model. The magnetic structures predicted by first-principles calculations as well as the Curie (Néel) temperatures obtained from Monte Carlo simulations are both in good agreement with experiments. A detailed analysis of the exchange parameters suggests that the Ruderman-Kittel-Kasuya-Yosida-type indirect exchange interactions and antiferromagnetic superexchange interactions coexist in these compounds. The magnetic order changes from ferromagnetic in GdN to antiferromagnetic in other Gd pnictides as a result of the increased ionic radius of a pnictide in the …
Defect Contributions To Conductivity In Poly(3-Hexylthiophene)?, A. N. Caruso, D.-Q. Feng, Yaroslav B. Losovyj, D. L. Schulz, Snjezana Balaz, Luis G. Rosa, Andrei Sokolov, Bernard Doudin, Peter A. Dowben
Defect Contributions To Conductivity In Poly(3-Hexylthiophene)?, A. N. Caruso, D.-Q. Feng, Yaroslav B. Losovyj, D. L. Schulz, Snjezana Balaz, Luis G. Rosa, Andrei Sokolov, Bernard Doudin, Peter A. Dowben
Peter Dowben Publications
We find evidence for a gradual change in the electronic properties of spin coated poly(3-hexylthiophene) thin films with temperature. The conduction properties appears to be mediated by hopping conduction dominated by a low density of defects states within the highest occupied molecular orbital to lowest unoccupied molecular orbital gap, not by a change in band gap. The photoemission and transport measurements indicate a loss of charge mobility or carrier concentration occurs with decreasing temperature, while the molecular configuration (through chain conjugation) also changes with temperature. The defects states identified by photoemission (–1.7 eV) as well as others contributing to the …