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Comparison Of The Temperature-Dependent Electronic Structure Of The Perovskites La0.65Ca0.35Mno3 (A=Ca, Ba), D.N. Mcilroy, C. Waldfried, Jiandi Zhang, Jaewu Choi, F. Foong, Sy_Hwang Liou, Peter A. Dowben
Comparison Of The Temperature-Dependent Electronic Structure Of The Perovskites La0.65Ca0.35Mno3 (A=Ca, Ba), D.N. Mcilroy, C. Waldfried, Jiandi Zhang, Jaewu Choi, F. Foong, Sy_Hwang Liou, Peter A. Dowben
Peter Dowben Publications
The electronic band structure and the local screening effects of the transition-metal perovskites La0.65A0.35MnO3 (A=Ba and Ca ) have been examined across the coupled magnetic-metallic phase transition using the techniques of angle-resolved photoemission, resonance photoemission, and inverse photoemission. Temperature-dependent band shifts of the eg and t2g bands of La0.65Ca0.35MnO3 have been observed. These changes in the observed electronic structure correlate with the phase transition, and are in qualitatively agreement with the predicted behavior associated with double exchange coupled with a dynamic Jahn-Teller distortion. Similar shifts were not observed …
Strain-Induced Distortion Of The Bulk Bands Of Gadolinium, Carlo Waldfried, D.N. Mcilroy, C.W. Hutchings, Peter A. Dowben
Strain-Induced Distortion Of The Bulk Bands Of Gadolinium, Carlo Waldfried, D.N. Mcilroy, C.W. Hutchings, Peter A. Dowben
Peter Dowben Publications
Thin films of gadolinium, approximately 8 ML thick, have been grown on the corrugated (112) surface of molybdenum and the electronic structure has been investigated with angle-resolved photoelectron spectroscopy. The unfavorable lattice match between the ‘‘steplike’’ Mo(112) substrate and the preferred hexagonally ordered Gd film results in an incommensurate Gd structure that appears to be ordered, but strained along the direction of the corrugations. The hexagonal Gd lattice is expanded by more than 20% along the ‘‘step’’ lines of the substrate, as determined from the reduced Brillouin-zone size along the ΓΣM high-symmetry line and low-energy electron diffraction. The induced strain …
Fabrication Of N-Type Nickel Doped B5 C1+Δ Homojunction And Heterojunction Diodes, Seong-Don Hwang, Ken Yang, Peter A. Dowben, Ahmad A. Ahmad, N.J. Ianno, J.Z. Li, J.Y. Lin, H.X. Jiang, D.N. Mcilroy
Fabrication Of N-Type Nickel Doped B5 C1+Δ Homojunction And Heterojunction Diodes, Seong-Don Hwang, Ken Yang, Peter A. Dowben, Ahmad A. Ahmad, N.J. Ianno, J.Z. Li, J.Y. Lin, H.X. Jiang, D.N. Mcilroy
Peter Dowben Publications
We have successfully nickel doped a boron carbide (B5C) alloy film. The nickel doped boron-carbide (Ni-B5C1+δ) thin films were fabricated from a single source carborane cage molecule and nickelocene [Ni(C5H5)2] using plasma enhanced chemical vapor deposition. Nickel doping transforms the highly resistive undoped film from a p-type material to an n-type material. This has been verified from the characteristics of diodes constructed of Ni-B5C1+δ on both n-type silicon and p-type B5C. The homojunction diodes exhibit excellent rectifying properties over a wide range of temperatures. ©1997 …
Auger Electron Spectroscopy Of Free Argon Clusters, A. Knop, D. N. Mcilroy, Peter A. Dowben, E. Rühl
Auger Electron Spectroscopy Of Free Argon Clusters, A. Knop, D. N. Mcilroy, Peter A. Dowben, E. Rühl
Peter Dowben Publications
Auger electron spectra and Auger yields of free argon clusm in the Ar(2p) excitation regime are reported. The Auger yield spectra show characteristic changes as a function of cluster size. The results indicate that the Auger yield signal originates primarily from the surface of the cluster. The results are compared to bulk-sensitive experimental techniques, such as total electron yields (TEY), zero kinetic energy electron (ZEKE) spectra for variable size clusters, as well as Auger yield spectra of condensed argon multilayers.
Experimental Evidence For The Dynamic Jahn-Teller Effect In La0.65Ca0.35Mno3, P. Dai, Jiandi Zhang, H.A. Mook, Sy_Hwang Liou, Peter A. Dowben, E. Ward Plummer
Experimental Evidence For The Dynamic Jahn-Teller Effect In La0.65Ca0.35Mno3, P. Dai, Jiandi Zhang, H.A. Mook, Sy_Hwang Liou, Peter A. Dowben, E. Ward Plummer
Peter Dowben Publications
Recently, it has been argued that a strong electron-phonon interaction arising from the Jahn-Teller splitting of the outer Mn d level plays a crucial role in understanding the nonmetal-to-metal transition observed in the La1-xAxMnO3 (A=Ca, Sr, Ba) system. We show, by neutron powder diffraction, that La0.65Ca0.35MnO3 exhibits an anomalous volume and oxygen/manganese displacement change around Tc, in qualitative agreement with the theoretical prediction.
Reduced Diameter Retractable Cylindrical Mirror Analyzer, Peter A. Dowben, David N. Mcilroy
Reduced Diameter Retractable Cylindrical Mirror Analyzer, Peter A. Dowben, David N. Mcilroy
Peter Dowben Publications
A single pass cylindrical mirror analyzer for use in charged particle analysis has reduced size for mounting on a simple manipulator. The reduced size of the analyzer allows for placement of the analyzer on a linear motion feedtrough mounted on a conflat flange for insertion into and retraction from the analysis position. The reduced size of the cylindrical mirror analyzer in combination with good instrument resolution results in a versatile charged particle analyzer.
Nickel Doping Of Boron Carbide Grown By Plasma Enhanced Chemical Vapor Deposition, Seong-Don Hwang, N.B. Remmes, Peter A. Dowben, D.N. Mcilroy
Nickel Doping Of Boron Carbide Grown By Plasma Enhanced Chemical Vapor Deposition, Seong-Don Hwang, N.B. Remmes, Peter A. Dowben, D.N. Mcilroy
Peter Dowben Publications
We have nickel doped boron carbide grown by plasma enhanced chemical vapor deposition. The source gas closo-1,2-dicarbadodecaborane (ortho-carborane) was used to grow the boron carbide, while nickelocene [Ni(C5H5)2] was used to introduce nickel into the growing film. The doping of nickel transformed a p-type, B5C material, relative to lightly doped n-type silicon, to an n-type material. Both n-n heterojunction diodes and n-p heterojunction diodes were constructed, using as substrates n- and p-type Si(111), respectively. With sufficient partial pressures of nickelocene in the plasma reactor, …
Optical Properties Of Boron Carbide (B5C) Thin Films Fabricated By Plasma-Enhanced Chemical-Vapor Deposition, Ahmad A. Ahmad, N.J. Ianno, P.G. Snyder, D. Welipitiya, D. Byun, Peter A. Dowben
Optical Properties Of Boron Carbide (B5C) Thin Films Fabricated By Plasma-Enhanced Chemical-Vapor Deposition, Ahmad A. Ahmad, N.J. Ianno, P.G. Snyder, D. Welipitiya, D. Byun, Peter A. Dowben
Peter Dowben Publications
Variable angle of incidence spectroscopic ellipsometry was used to determine the optical constants near the band edge of boron carbide (B5C) thin films deposited on glass and n-type Si(111) via plasma-enhanced chemical-vapor deposition. The index of refraction n, the extinction coefficient k, and the absorption coefficient are reported in the photon energy spectrum between 1.24 and 4 eV. Ellipsometry analysis of B5C films on silicon indicates a graded material, while the optical constants of B5C on glass are homogeneous. Line shape analyses of absorption data for the films on glass indicate …
Auger Electron Spectroscopy Of Free Argon Clusters, A. Knop, D.N. Mcilroy, Peter A. Dowben, E. Ruhl
Auger Electron Spectroscopy Of Free Argon Clusters, A. Knop, D.N. Mcilroy, Peter A. Dowben, E. Ruhl
Peter Dowben Publications
Auger electron spectra and Auger yields of free argon clusters in the Ar(2p) excitation regime are reported. The Auger yield spectra show characteristic changes as a function of cluster size. The results indicate that the Auger yield signal originates primarily from the surface of the clusters. The results are compared to bulk-sensitive experimental techniques, such as total electron yields (TEY), zero kinetic energy electron (ZEKE) spectra for variable size clusters, as well as Auger yield spectra of condensed argon multilayers.
Fabrication Of Large Arrays Of Micron-Scale Magnetic Features By Selective Area Organometallic Chemical Vapor Deposition, D. Welipitiya, Y.L. He, Jiandi Zhang, P.I. Oden, T. Thundat, R.J. Warmack, Ismail Gobulukoglu, Z.S. Shan, David J. Sellmyer, Peter A. Dowben
Fabrication Of Large Arrays Of Micron-Scale Magnetic Features By Selective Area Organometallic Chemical Vapor Deposition, D. Welipitiya, Y.L. He, Jiandi Zhang, P.I. Oden, T. Thundat, R.J. Warmack, Ismail Gobulukoglu, Z.S. Shan, David J. Sellmyer, Peter A. Dowben
Peter Dowben Publications
We demonstrate that it is possible to deposit a wide range of magnetic features, using photoassisted selective area organometallic chemical vapor deposition. Large arrays of identical micron-scale Ni features were deposited on a Si(111) wafer by this method. Their magnetic properties were studied by alternating gradient force magnetometry as well as magnetic force microscopy. Our morphological and magnetic measurements show that the structures are spatially well defined, and the magnetic properties are related to the structural shapes of the features. This method can be adapted to the fabrication of smaller-scale magnetic and electronic devices. ©1996 American Institute of Physics.
Spin Polarization Of The Conduction Bands And Secondary Electrons Of Gd(0001), Dongqi Li, J. Pearson, S.D. Bader, D.N. Mcilroy, C. Waldfried, Peter A. Dowben
Spin Polarization Of The Conduction Bands And Secondary Electrons Of Gd(0001), Dongqi Li, J. Pearson, S.D. Bader, D.N. Mcilroy, C. Waldfried, Peter A. Dowben
Peter Dowben Publications
Angle- and spin-resolved photoemission was utilized to investigate the 5d bulk bands and the surface state of Gd(0001) in the temperature range of 130–350 K. The bulk bands at 1–2 eV below the Fermi energy EF show Stoner-like behavior, while the temperature dependence of the surface state near EF indicates spin-mixing behavior due to fluctuating local 5d moments. The secondary electron spectra of the Gd surfaces both before and after initial oxygen adsorption show a polarization dip at low kinetic energies due to the extra scattering channel for minority electrons via the unoccupied 4f level. The temperature dependencies …
Oxygen Induced Suppression Of The Surface Magnetization Of Gd(0001), D.N. Mcilroy, C. Waldfried, Dongqi Li, J. Pearson, S.D. Bader, D.-J. Huang, P.D. Johnson, R.F. Sabiryanov, Sitaram Jaswal, Peter A. Dowben
Oxygen Induced Suppression Of The Surface Magnetization Of Gd(0001), D.N. Mcilroy, C. Waldfried, Dongqi Li, J. Pearson, S.D. Bader, D.-J. Huang, P.D. Johnson, R.F. Sabiryanov, Sitaram Jaswal, Peter A. Dowben
Peter Dowben Publications
The effects of oxygen adsorption on the surface magnetization of Gd(0001) have been determined by measuring the polarization of the Gd 4f core levels and the oxygen induced states with spin-resolved photoemission. Calculations of the partial density of states of O/Gd(0001) using the LMTO-ASA method support the photoemission measurements, which indicate that oxidation occurs at low coverages. The loss of surface magnetic order with oxygen exposure is explained in terms of decreasing indirect coupling.
Ultraviolet And Electron Radiation Induced Fragmentation Of Adsorbed Ferrocene, Dulip Welipitiya, A. Green, J.P. Woods, Peter A. Dowben, Brian W. Robertson, Dongjin Byun, Jiandi Zhang
Ultraviolet And Electron Radiation Induced Fragmentation Of Adsorbed Ferrocene, Dulip Welipitiya, A. Green, J.P. Woods, Peter A. Dowben, Brian W. Robertson, Dongjin Byun, Jiandi Zhang
Peter Dowben Publications
From thermal desorption spectroscopy we find that ferrocene, Fe(C5H5)2, adsorbs and desorbs associatively on Ag(100). Photoemission results indicate that the initially adsorbed surface species closely resembles that of molecular ferrocene. The shift in photoemission binding energies relative to the gas phase is largely independent of the molecular orbital. We find that ultraviolet light does lead to partial fragmentation of the ferrocene and that the molecular fragments are much more strongly bound to the surface than the associatively adsorbed ferrocene. Since fragmentation occurs only in the presence of incident radiation, selective area deposition from this …
Fabrication Of Boron-Carbide Boron Heterojunction Devices, Seong-Don Hwang, Dongjin Byun, N.J. Ianno, Peter A. Dowben, H.R. Kim
Fabrication Of Boron-Carbide Boron Heterojunction Devices, Seong-Don Hwang, Dongjin Byun, N.J. Ianno, Peter A. Dowben, H.R. Kim
Peter Dowben Publications
We have succeeded in the fabrication of a boron–carbide/boron diode on an aluminum substrate, and a boron–carbide/boron junction field effect transistor. Our 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. ©1996 American Institute of Physics.