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Full-Text Articles in Physics
Characterization Of The Native Cr2O3 Oxide Surface Of Cro2, Ruihua Cheng, B. Xu, C.N. Borca, Andrei Sokolov, C.S. Yang, Lu Yuan, Sy_Hwang Liou, Bernard Doudin, Peter A. Dowben
Characterization Of The Native Cr2O3 Oxide Surface Of Cro2, Ruihua Cheng, B. Xu, C.N. Borca, Andrei Sokolov, C.S. Yang, Lu Yuan, Sy_Hwang Liou, Bernard Doudin, Peter A. Dowben
Peter Dowben Publications
Using photoemission and inverse photoemission, we have been able to characterize the Cr2O3 oxide surface of CrO2 thin films. The Cr2O3 surface oxide exhibits a band gap of about 3 eV, although the bulk CrO2 is conducting. The thickness of this insulating Cr2O3 layer is twice the photoelectron escape depth which is about 2 nm thick. The effective Cr2O3 surface layer Debye temperature, describing motion normal to the surface, is about 370 K. From a comparison of CrO2 films grown by different techniques, with different …
Evidence For Temperature Dependent Moments Ordering In Ferromagnetic Nimnsb(100), C.N. Borca, Takashi Komesu, Hae-Kyung Jeong, Peter A. Dowben, Delia Ristoiu, Ch. Hordequin, J. P. Nozie`Res, J. Pierre, Shane Stadler, Y. U. Idzerda
Evidence For Temperature Dependent Moments Ordering In Ferromagnetic Nimnsb(100), C.N. Borca, Takashi Komesu, Hae-Kyung Jeong, Peter A. Dowben, Delia Ristoiu, Ch. Hordequin, J. P. Nozie`Res, J. Pierre, Shane Stadler, Y. U. Idzerda
Peter Dowben Publications
From magnetic circular dichroism measurements of the Heusler alloy NiMnSb, in combination with other techniques, we show that a dramatic increase in the Mn and Ni moments occurs below a ‘‘crossover’’ transition temperature of about 80–100 K. This phase transition is well below the Curie temperature of NiMnSb (~730 K). While the spin polarization near the Fermi level, from spin-polarized inverse photoemission, remains very high for kII50, it is unlikely that NiMnSb is a half-metallic ferromagnet near room temperature.
Layer-Resolved Spin Polarization In Sb Overlayers On Nimnsb, Ralph Skomski, T. Komesu, C.N. Borca, H.-K. Jeong, Peter A. Dowben, D. Ristoiu, J.P. Nozie´Res
Layer-Resolved Spin Polarization In Sb Overlayers On Nimnsb, Ralph Skomski, T. Komesu, C.N. Borca, H.-K. Jeong, Peter A. Dowben, D. Ristoiu, J.P. Nozie´Res
Peter Dowben Publications
The magnetism of antimony overlayers on a ferromagnetic substrate is investigated by spin-polarized inverse photoemission and explained in terms of a spin-dependent envelope-function approximation (SDEFA). The atomic structure of the films, which were deposited by sputtering Sb onto a NiMnSb(001) substrate, is characterized by a unique combination of three features: (i) NiMnSb is a highly spin-polarized semi-Heusler alloy predicted to be halfmetallic, (ii) antimony is a semimetal, exhibiting a band structure reminiscent of indirect-gap semiconductors, and (iii) the small lattice mismatch ensures a well-controlled interface. Combined x-ray absorption spectroscopy and spin-polarized inverse photoemission yield a layer-resolved spin polarization decaying on …
A Surface Insulator-To-Conductor Phase Transition In Colossal Magnetoresistive Manganese Perovskites Thin Films, C.N. Borca, Bo Xu, Takashi Komesu, Hae-Kyung Jeong, Sy-Hwang Liou, Peter A. Dowben
A Surface Insulator-To-Conductor Phase Transition In Colossal Magnetoresistive Manganese Perovskites Thin Films, C.N. Borca, Bo Xu, Takashi Komesu, Hae-Kyung Jeong, Sy-Hwang Liou, Peter A. Dowben
Peter Dowben Publications
We have observed a distinct surface phase transition for an important class of colossal magnetoresistive materials, La0.65D0.35MnO3 (with D = Sr, Pb) occurring in a surface layer compositionally different from the bulk. The surface phase transition occurs around 240 K compared to 350 K for the bulk and is fundamentally different. In the bulk, a ferromagnetic metal to paramagnetic ‘bad metal’ occurs, while the lower-temperature surface transition is from an n-type (in case of La0.65Sr0.35MnO3) or a p-type (in case of La0.65Pb0.35MnO3 …
A Landau-Ginzburg Description Of Sb Overlayers, Ralph Skomski, T. Komesu, H.-K. Jeong, C.N. Borca, Peter A. Dowben, D. Ristoiu, J.P. Nozieres
A Landau-Ginzburg Description Of Sb Overlayers, Ralph Skomski, T. Komesu, H.-K. Jeong, C.N. Borca, Peter A. Dowben, D. Ristoiu, J.P. Nozieres
Peter Dowben Publications
The spin polarization of Sb overlayers on the semi-Heusler alloy NiMnSb is investigated in terms of the Landau-Ginzburg approach. The half-metallic semi-Heusler alloy NiMnSb acts as a ferromagnetic perturbation and induces a spin polarization in the semimetallic Sb overlayer. Using a Gaussian approximation, the propagation of the spin perturbation in the overlayer is calculated. The results are compared with spin-polarized inverse photoemission spectroscopy (SPIPES) results and with recent spin-dependent envelope-function approximation (SDEFA) predictions. The Landau-Ginzburg parameters are both band-structure and temperature dependent, and it is argued that thermal spin excitations lead to an injection depth decreasing as 1//T law at …
Interplay Between Plasmons And The Band Structure For The Mo(112) Surface, I. N. Yakovkin, Jiandi Zhang, Peter A. Dowben
Interplay Between Plasmons And The Band Structure For The Mo(112) Surface, I. N. Yakovkin, Jiandi Zhang, Peter A. Dowben
Peter Dowben Publications
Recent photoemission and inverse photoemission results for the Mo(112) surface are discussed in the framework of the calculated band structure. For the Mo(112) surface, the main photoemission features combine contributions from both the surface and the bulk. Except for those photon energies near to excitations of the bulk and multipole surface plasmons, the comparison of the bulk band structure, along the k points normal to the surface, shows a good agreement with photoemission spectra in the position of the critical points. The dominant surface states at Г̅̅̅ are found to have the a1 symmetry, while the band along Г̅̅̅ …
High Resolution Charged Particle-Energy Detecting, Multiple Sequential Stage, Compact, Small Diameter, Retractable Cylindrical Mirror Analyzer System, And Method Of Use, Peter A. Dowben, Carlo Waldfried, Tara J. Mcavoy, David N. Mcilroy
High Resolution Charged Particle-Energy Detecting, Multiple Sequential Stage, Compact, Small Diameter, Retractable Cylindrical Mirror Analyzer System, And Method Of Use, Peter A. Dowben, Carlo Waldfried, Tara J. Mcavoy, David N. Mcilroy
Peter Dowben Publications
Disclosed is a compact, small diameter, high resolution charged particle-energy detecting, retractable cylindrical mirror analyzer system. Multiple sequential stages enable charged particle-energy detection with an improved resolution as compared to that possible where only a single stage is utilized. The relatively small size allows for positioning, via a manipulator of the cylindrical mirror analyzer system, which is attached to a linear motion feedthrough mounted on a conflat flange of a vacuum system.
Self-Assembled Fe Nanowires Using Organometallic Chemical Vapor Deposition And Caf2 Masks On Stepped Si(111), J.-L. Lin, D.Y. Petrovykh, A. Kirakosian, H. Rauscher, F.J. Himpsel, Peter A. Dowben
Self-Assembled Fe Nanowires Using Organometallic Chemical Vapor Deposition And Caf2 Masks On Stepped Si(111), J.-L. Lin, D.Y. Petrovykh, A. Kirakosian, H. Rauscher, F.J. Himpsel, Peter A. Dowben
Peter Dowben Publications
Linear arrays of 3 nm wide Fe stripes with 15 nm spacing are fabricated by self-assembly. They are formed by photolysis of ferrocene that is selectively adsorbed between CaF2 stripes. An ultraviolet nitrogen laser removes the organic ligands from ferrocene. Arrays of CaF2 stripes serve as masks, which are self-assembled on a stepped Si(111) surface. Scanning tunneling microscopy is used to investigate the surface morphology during growth. A generalization of this method to other wire materials is discussed.
Potential Phase Control Of Chromium Oxide Thin Films Prepared By Laser-Initiated Organometallic Chemical Vapor Deposition, Ruihua Cheng, C.N. Borca, Peter A. Dowben, Shane Stadler, Y.U. Idzerda
Potential Phase Control Of Chromium Oxide Thin Films Prepared By Laser-Initiated Organometallic Chemical Vapor Deposition, Ruihua Cheng, C.N. Borca, Peter A. Dowben, Shane Stadler, Y.U. Idzerda
Peter Dowben Publications
We have used laser-initiated chemical vapor deposition to grow the chromium oxide thin films through the oxidation of Cr(CO)6 in an oxygen environment. While both Cr2O3 and CrO2 are present in the film, the relative weight of each phase depends on the oxygen partial pressure. The Curie temperature of the film increases and approaches the bulk TC of CrO2 (397 K) as the partial oxygen pressure is increased. © 2001 American Institute of Physics. [DOI: 10.1063/1.1343846]
Comparison Of Aluminum And Sodium Doped Poly(Vinylidene Fluoride-Trifluoroethylene) Copolymers By X-Ray Photoemission Spectroscopy, B. Xu, Jaewu Choi, C.N. Borca, Peter A. Dowben, A.V. Sorokin, S.P. Palto, N.N. Petukhova, S.G. Yudin
Comparison Of Aluminum And Sodium Doped Poly(Vinylidene Fluoride-Trifluoroethylene) Copolymers By X-Ray Photoemission Spectroscopy, B. Xu, Jaewu Choi, C.N. Borca, Peter A. Dowben, A.V. Sorokin, S.P. Palto, N.N. Petukhova, S.G. Yudin
Peter Dowben Publications
The chemical interaction between the simple metals, aluminum and sodium, and crystalline copolymer thin films of vinylidene fluoride (70%) with trifluoroethylene (30%), has been studied using x-ray photoemission spectroscopy. Aluminum and sodium metalize the polymer differently and different binding sites for the two metals can be inferred from the corresponding core level shifts. Aluminum leads to enhanced screening of final photoemission states associated with the polymer, while sodium doping strongly influences the fluorine, but perturbs the carbon backbone only slightly. © 2001 American Institute of Physics. [DOI: 10.1063/1.1340858]
Aluminum Doping Of Poly(Vinylidene Fluoride With Trifluoroethylene) Copolymer, B. Xu, C.N. Borca, Stephen Ducharme, A.V. Sorokin, Peter A. Dowben, V.M. Fridkin, S.P. Palto, N.N. Petukhova, S.G. Yudin
Aluminum Doping Of Poly(Vinylidene Fluoride With Trifluoroethylene) Copolymer, B. Xu, C.N. Borca, Stephen Ducharme, A.V. Sorokin, Peter A. Dowben, V.M. Fridkin, S.P. Palto, N.N. Petukhova, S.G. Yudin
Peter Dowben Publications
The interface between aluminum and crystalline copolymer thin film of vinylidene fluoride (70%) with trifluoroethylene (30%) [PVDF-TrFE] has been studied. The ratio of carbon 1s and aluminum 2p core level photoemission peak intensities changes little with increasing emission angle after deposition of 5 Å aluminum on the surface of PVDF-TrFE. This indicates that the distribution of aluminum atoms in the copolymer film is quite uniform in the near surface region and that the interface between PVDF-TrFE and aluminum is not abrupt. There is evidence for changes in photohole screening with aluminum doping within the polymer film.
Changes In Electron-Phonon Coupling Across A Bulk Phase Transition In Copolymer Films Of Vinylidene Fluoride (70%) With Trifluoroethylene (30%), C.N. Borca, Shireen Adenwalla, Jaewu Choi, Lee Robertson, H. You, V.M. Fridkin, S.P. Palto, N. Petukhova, Peter A. Dowben
Changes In Electron-Phonon Coupling Across A Bulk Phase Transition In Copolymer Films Of Vinylidene Fluoride (70%) With Trifluoroethylene (30%), C.N. Borca, Shireen Adenwalla, Jaewu Choi, Lee Robertson, H. You, V.M. Fridkin, S.P. Palto, N. Petukhova, Peter A. Dowben
Peter Dowben Publications
We present evidence for a change in electron-phonon coupling across a bulk phase transition. Below the lattice stiffening transition at around 160 K, there is a change in the diffracted peak width observed by neutron and X-ray scattering techniques. Also, the electronic band structure of the copolymer is shifting in binding energy below 160 K, decreasing the density of states near the Fermi level. The value of the effective Debye temperature above the transition temperature is approximately 50 K, while below 160 K, the value of the Debye parameter is 245 K. We postulate that the coupling between electrons and …