Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 10 of 10
Full-Text Articles in Physics
Magnetoresistance In Boron Carbide Junctions, L. Bernard, J. Monson, Andrei Sokolov, Zong-Yuan Liu, C.S. Yang, Peter A. Dowben, Bermard Doudin, A. Harken, P. Welsch, B. W. Robertson
Magnetoresistance In Boron Carbide Junctions, L. Bernard, J. Monson, Andrei Sokolov, Zong-Yuan Liu, C.S. Yang, Peter A. Dowben, Bermard Doudin, A. Harken, P. Welsch, B. W. Robertson
Peter Dowben Publications
Photoemission and electric transport properties of ferromagnet–insulator–ferromagnet junctions with boron carbide (C2B10) dielectric barrier are presented. Using a non-oxide barrier confidence avoids oxidation of the interfaces with the ferromagnetic layers. Photoemission confirms chemical abruptness of the interface. Magnetoresistance ratios reaching 50% are observed at low temperatures, and large nonlinearity in the current–voltage curves show that impurities in the junctions play a key role. © 2003 American Institute of Physics.
Boron-Carbide And Boron Rich Rhobohedral Based Transistors And Tunnel Diodes, Peter A. Dowben
Boron-Carbide And Boron Rich Rhobohedral Based Transistors And Tunnel Diodes, Peter A. Dowben
Peter Dowben Publications
The present invention relates to the fabrication of a boron carbide/boron semiconductor devices. The results suggest that with respect to the approximately 2 eV band gap pure boron material, 0.9 eV band gap boron carbide (B5C) acts as a p-type material. Both boron and boron carbide (B5C) thin films were fabricated from single source borane cage molecules using plasma enhanced chemical vapor deposition (PECVD). Epitaxial growth does not appear to be a requirement. We have doped boron carbide grown by plasma enhanced chemical vapor deposition. The source gas close- 1,2-dicarbadecaborane (orthocarborane) was used to grow the …
Nanoscale Polarization Manipulation And Conductance Switching In Ultrathin Films Of A Ferroelectric Copolymer, Hongwei Qu, Wei Yao, T. Garcia, Jiandi Zhang, A.V. Sorokin, Stephen Ducharme, Peter A. Dowben, V.M. Fridkin
Nanoscale Polarization Manipulation And Conductance Switching In Ultrathin Films Of A Ferroelectric Copolymer, Hongwei Qu, Wei Yao, T. Garcia, Jiandi Zhang, A.V. Sorokin, Stephen Ducharme, Peter A. Dowben, V.M. Fridkin
Peter Dowben Publications
We report the direct observation of induced molecular reorientation on a ferroelectric copolymer with a scanning tunneling microscope (STM). Ultrathin copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%) revealed a quasihexagonal close-packing structure with long-range polymer chain ordering. By flipping the polarity of the STM tip bias voltage, a reversal of local polarization was observed through an apparent lattice shift and was accompanied by an asymmetric ‘‘diode-like’’ character in tunneling current I(V). These results clearly demonstrated conductance switching behavior on nanoscale with local polarization reversal. © 2003 American Institute of Physics.
Finite-Temperature Spin Polarization In Half-Metallic Ferromagnets, Peter A. Dowben, Ralph Skomski
Finite-Temperature Spin Polarization In Half-Metallic Ferromagnets, Peter A. Dowben, Ralph Skomski
Peter Dowben Publications
The temperature dependence of the spin polarization of half-metallic ferromagnets is investigated. A unitary spinor transformation shows that the corresponding spin mixing goes beyond finite-temperature smearing of the Fermi level, leading to a nonzero density of states in the gap of the insulating spin channel. As a consequence, the resistance ratio of the two spin channels changes from infinity to some finite value and, in a strict sense, half-metallic ferromagnetism is limited to zero temperature. Bloch-type spin waves and crystal imperfections contribute to the density of states in the gap but only partly explain the pronounced changes at about 0.2 …
Substrate Dependent Bonding Of Chemisorbed 1,1’-Biphenyl-4,4’-Dimethanethiol, A. N. Caruso, R. Rajesekaran, Jody G. Redepenning, Yaroslav B. Losovyj, Peter A. Dowben
Substrate Dependent Bonding Of Chemisorbed 1,1’-Biphenyl-4,4’-Dimethanethiol, A. N. Caruso, R. Rajesekaran, Jody G. Redepenning, Yaroslav B. Losovyj, Peter A. Dowben
Peter Dowben Publications
We compare the adsorption of 1,1’-biphenyl-4,4’-dimethanethiol (BPDMT) on gold and cobalt surfaces. The molecular orbitals, identified from combined photoemission and inverse photoemission studies, exhibit shifts in binding energies with different deposition methods and substrates. These shifts indicate that this potential molecular dielectric exhibits stronger bonding to cobalt surfaces than gold surfaces.
The Adsorption Of Orthocarborane On Cobalt, L. Bernard, A. N. Caruso, Bo Xu, Bernard Doudin, Peter A. Dowben
The Adsorption Of Orthocarborane On Cobalt, L. Bernard, A. N. Caruso, Bo Xu, Bernard Doudin, Peter A. Dowben
Peter Dowben Publications
The adsorption of closo-1,2 dicarbadodecaborane (orthocarborane) on evaporated cobalt thin films has been investigated by combined photoemission and inverse photoemission studies. The adsorption of these icosahedral molecules does not strongly perturb the electronic structure of the underlying cobalt. As was previously observed with adsorption on Cu(100), electron induced decomposition of adsorbed orthocarborane decreases the HOMO–LUMO gap. The X-ray photoemission spectra before and after orthocarborane adsorption confirm that the interface with cobalt is abrupt. These results suggest that chemical vapor deposition, via the decomposition of orthocarborane, may be an effective method for fabricating dielectric barrier layers, without utilizing oxides. This …
Consideration Of Possible Mass And Velocity Corrections To Magnetic Cluster Experiments, Z.Y. Liu, Peter A. Dowben, A.P. Popov, David P. Pappas
Consideration Of Possible Mass And Velocity Corrections To Magnetic Cluster Experiments, Z.Y. Liu, Peter A. Dowben, A.P. Popov, David P. Pappas
Peter Dowben Publications
Gadolinium occurs, in natural abundance, as several isotopes. The possible combinations of different gadolinium isotopes dictates that even for a fixed number of atoms in the cluster, clusters of gadolinium atoms will exhibit a range of masses. This and the expected consequence of the translation energy distributions are explored as possible corrections to Stern-Gerlach cluster beam-deflection experiments. Upon closer inspection of the experimental data, we find that the translation energy plus the vibrational temperature distribution may be inhomogeneous. This could be the origin of a long tail to high deflections in the experimental deflection profiles, at low cluster temperatures, in …
Magnetic Coupling In Co/Cr2O3/Cro2 "Trilayer" Films, Ruihau Cheng, A. N. Caruso, Lu Yuan, Sy_Hwang Liou, Peter A. Dowben
Magnetic Coupling In Co/Cr2O3/Cro2 "Trilayer" Films, Ruihau Cheng, A. N. Caruso, Lu Yuan, Sy_Hwang Liou, Peter A. Dowben
Peter Dowben Publications
The ferromagnetic coupling between Co and CrO2 , through an insulator (Cr2O3) was characterized by in situ magneto-optic Kerr effect. By evaporating 20–60 Å Co thin films on top of epitaxial CrO2 films, a Co/Cr2O3 /CrO2 trilayer system can be readily fabricated; this is possible because the native surface layer of CrO2 is Cr2O3 . In situ x-ray photoemission studies show that the Co is oxidized at the interface between Co and Cr2O3 , so that the system more resembles Co/CoO/Cr2O …
Electronic Structure Of Eras(100), Takashi Komesu, Hae-Kyung Jeong, Jaewu Choi, C.N. Borca, Peter A. Dowben, A.G. Petukhov, B.D. Schultz, C.J. Palmstrom
Electronic Structure Of Eras(100), Takashi Komesu, Hae-Kyung Jeong, Jaewu Choi, C.N. Borca, Peter A. Dowben, A.G. Petukhov, B.D. Schultz, C.J. Palmstrom
Peter Dowben Publications
The experimental band structure of the rare-earth pnictide erbium arsenide (ErAs), grown epitaxially on GaAs(100), has been mapped out using photoelectron spectroscopy and inverse photoemission spectroscopy. The electronic structure is dominated by bulk bands qualitatively consistent with the calculated band structure. A number of additional nondispersing 4 f multiplet levels can be identified in the valence-band structure as well as at least one surface resonance band. From symmetry selection rules, photoemission provides strong evidence that the Δ5 (or e) symmetry bands are a consequence of hybridization between Er and As, while the Δ 1 (or a1) symmetry …
Comparison Of The Theoretical And Experimental Band Structure Of Poly(Vinylidene Fluoride) Crystal, Chun-Gang Duan, Wai-Ning Mei, J.R. Hardy, Stephen Ducharme, Jaewu Choi, Peter A. Dowben
Comparison Of The Theoretical And Experimental Band Structure Of Poly(Vinylidene Fluoride) Crystal, Chun-Gang Duan, Wai-Ning Mei, J.R. Hardy, Stephen Ducharme, Jaewu Choi, Peter A. Dowben
Peter Dowben Publications
The electronic structure and band symmetries of the ferroelectric phase of poly (vinylidene fluoride) (PVDF) are studied by using the first-principles density-functional method. Our calculated results agree well with the angle-resolved photoemission experiments. We find that the PVDF crystal has an energy gap of about 6 eV at the Γ-point. Large dispersion of the valence band is found only along the chain direction, which is consistent with the quasi-one-dimensional nature of PVDF. In particular, the band symmetries of the valence states deduced theoretically are in good agreement with experiment. Finally, further investigations on the electronic structure of poly(trifluoroethylene) (PTrFE) reveal …