Open Access. Powered by Scholars. Published by Universities.®

Physics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Peter Dowben Publications

Articles 271 - 284 of 284

Full-Text Articles in Physics

Chemical Vapor Deposition Of Boron And Boron Nitride From Decaborane(L4) A), Yoon Gi Kim, Peter A. Dowben, J.T. Spencer, G.O. Ramseyer Jul 1989

Chemical Vapor Deposition Of Boron And Boron Nitride From Decaborane(L4) A), Yoon Gi Kim, Peter A. Dowben, J.T. Spencer, G.O. Ramseyer

Peter Dowben Publications

We have investigated photoassisted, plasma enhanced chemical vapor deposition and pyrolytic deposition of boron from decaborane (B10H14) and boron nitride from decaborane combined with nitrogen or ammonia. The use of decaborane for depositing boron and boron nitride thin films is seen as a viable alternative to diborane or boron halides.

Go to article

The Decomposition Of [Mn(Co)5]2(Μ-Sih2), G.T. Stauf, Peter A. Dowben, K. Emrich, W. Hirschwald, N.M. Boag May 1989

The Decomposition Of [Mn(Co)5]2(Μ-Sih2), G.T. Stauf, Peter A. Dowben, K. Emrich, W. Hirschwald, N.M. Boag

Peter Dowben Publications

The prospect of using chemical vapor deposition to deposit mixed metals and silicides from a single source compound is attractive but largely uninvestigated. Studies of decomposition energies of such compounds are nearly nonexistent. One such compound which has successfully been used to make a silicide coating is [Mn(CO)5 12 (μ-SiH2). We have used electron impact mass spectroscopy, photoionization mass spectroscopy, and photoabsorption to determine bond energies within this compound. The combination of methods allows a high degree of confidence in the resultant ionization and fragment appearance potentials. Some possible mechanisms of decomposition are discussed. A complete …

Go to article

The Influence Of Crystallographic Order Upon The Electronic Structure Of Thin Mercury Overlayers, Peter A. Dowben, M. Onellion, Shikha Varma, Y.J. Kime, J.L. Erskine May 1989

The Influence Of Crystallographic Order Upon The Electronic Structure Of Thin Mercury Overlayers, Peter A. Dowben, M. Onellion, Shikha Varma, Y.J. Kime, J.L. Erskine

Peter Dowben Publications

Thin ( 1-7 monolayer) well-ordered, disordered, and liquid Hg overlayers on Ag(100) have been investigated with angle resolved photoemission and low-energy electron diffraction. The well-ordered overlayers exhibit new electronic states as a result of the strained, cubic, overlayer crystallographic structure. The new electronic states depend upon the long-range crystallographic order of the overlayer, not simply the local crystallographic symmetry. The photoemission cross section and branching ratio of the 5d mercury states depends on the overlayer long-range crystallographic order and cannot be explained by photoelectron diffraction.

Go to article

Summary Abstract: Formation Of Cr2N Overlayers On A Fe/Cr{110} Crystal, H. Ruppender, M. Grunze, Peter A. Dowben May 1988

Summary Abstract: Formation Of Cr2N Overlayers On A Fe/Cr{110} Crystal, H. Ruppender, M. Grunze, Peter A. Dowben

Peter Dowben Publications

In this communication we summarize our experiments related to the formation of chromium surface nitride layers on a Fe72Cr28{110} surface. These surface nitrides were produced by (i) exposure to molecular nitrogen, (ii) exposure to ammonia, and (iii) segregation of nitrogen to the crystal surface. It was found in all cases that the nitrogen concentration in the selvedge scales linearly with the chromium concentration and that chromium segregation is the rate determining step for the formation of a surface nitride.

Go to article

Interaction Of Hg Overlayers With An Ag(100) Surface, Peter A. Dowben, Y.J. Kime, Shikha Varma, M. Onellion, J.L. Erskine Aug 1987

Interaction Of Hg Overlayers With An Ag(100) Surface, Peter A. Dowben, Y.J. Kime, Shikha Varma, M. Onellion, J.L. Erskine

Peter Dowben Publications

The electronic band structure of one, two, and five monolayers of Hg on Ag(100) has been investigated by angle-resolved photoemission. Hg overlayers on Ag(100) form metastable structures that develop via Frank–van der Merwe growth modes. Hg-Hg hybridization results in the formation of a two-dimensional band structure while hybridization of Hg with the underlying Ag(100) substrate results in the adoption of bulklike characteristics for some Hg-induced bands. The Hg-Hg as well as Hg-Ag interactions are discussed.

Go to article

The Stability And Decomposition Of Gaseous Chloroferrocenes, S. Barfuss, M. Grade, W. Hirschwalde, W. Rosinger, N.M. Boag, D.C. Driscoll, Peter A. Dowben Jul 1987

The Stability And Decomposition Of Gaseous Chloroferrocenes, S. Barfuss, M. Grade, W. Hirschwalde, W. Rosinger, N.M. Boag, D.C. Driscoll, Peter A. Dowben

Peter Dowben Publications

The ionic and neutral decomposition of gaseous ferrocene, 1, 1'-dichloroferrocene and 1, 1', 2,2'- tetrachloroferrocene, has been investigated via photon and electron induced ionization mass spectroscopy. The thermodynamic cycle incorporating the ionic and neutral fragments of ferrocene has been constructed. Elimination reactions in the decomposition of the dichloroferrocene and tetrachloroferrocenes have been identified.

Go to article

Structure-Induced Electronic States For Hg Overlayers On Ag(100), M. Onellion, J.L. Erskine, Y.J. Kime, Shikha Varma, Peter A. Dowben Jun 1986

Structure-Induced Electronic States For Hg Overlayers On Ag(100), M. Onellion, J.L. Erskine, Y.J. Kime, Shikha Varma, Peter A. Dowben

Peter Dowben Publications

Angle-resolved photoemission was used to observe the electronic band structure of one and two monolayers of Hg on Ag(100). Evidence for new Hg electronic states and band structure arising from the hybridization of the atomic 5d5/2 orbitals is presented. Low-energy electron diffraction results indicate that the Hg overlayers assume the face-centered-cubic (fcc) structure of the Ag(100) substrate, which is not the natural (rhombohedral) structure of bulk Hg. The new electronic states are induced as a result of the bonding of Hg atoms with adjacent metal atoms.

Go to article

Surface Segregation In Binary Alloys, Uresh Vahalia, Peter A. Dowben, Allen Miller May 1986

Surface Segregation In Binary Alloys, Uresh Vahalia, Peter A. Dowben, Allen Miller

Peter Dowben Publications

A semiempirical calculation is outlined that allows analysis of experimental results for the apparent surface concentration of binary alloys, obtained by x-ray photoelectron spectroscopy, (XPS). A segregation profile giving the enrichment of the segregating element at and near the surface is obtained from the analysis. Using previously published data for Cu 17 Ni 83 ( 100) and Cu 17 Ni 83 ( 111 ), it is shown that copper segregation is not restricted to the first few layers, but instead extends significantly into the selvedge (near-surface) region. This occurrence is not explainable by the use of present ideal solution models. …

Go to article

Ionic And Neutral Decompssition Of Gaseous Bromochloromethanes, D.C. Driscoll, J.A. Bishop, B.J. Sturm, Peter A. Dowben, C.G. Olsen May 1986

Ionic And Neutral Decompssition Of Gaseous Bromochloromethanes, D.C. Driscoll, J.A. Bishop, B.J. Sturm, Peter A. Dowben, C.G. Olsen

Peter Dowben Publications

The ionization potentials for CCl 4, CCl 3Br, CBr 2Cl 2, CBr 4, CCl 3, and CBr 3 have been measured using electron impact techniques. These numbers have been combined with previously published thermodynamic values in order to construct thermodynamic cycles for ionic and neutral decomposition of the bromochloromethanes. The n to σ*, n to s, and n to p electronic transition energies have also been determined on the basis of photoabsorption spectra.

Go to article

Epitaxial Growth Of Iron Iodide Films On Fe(L10), D.R. Mueller, T.N. Rhodin, Peter A. Dowben May 1986

Epitaxial Growth Of Iron Iodide Films On Fe(L10), D.R. Mueller, T.N. Rhodin, Peter A. Dowben

Peter Dowben Publications

The interaction of iodine vapor on an Fe(110) single crystal surface at room temperature has been investigated primarily through the use of LEED and UPS. Both a series of chemisorbed overlayers and an epitaxial iodide layer are observed. Iodide formation proceeds through an island growth mechanism with the iodide basal plane parallel to the Fe(110) surface. Evidence is presented that the defects introduced on the surface during argon ion sputtering may be important as nucleation sites for iodide growth. The results are compared with the results of previous studies.

Go to article

Angle-Resolved Photoemission From Bromine Chemisorbed On Ni(100), Peter A. Dowben, Y. Sakisaka, T.N. Rhodin Jul 1985

Angle-Resolved Photoemission From Bromine Chemisorbed On Ni(100), Peter A. Dowben, Y. Sakisaka, T.N. Rhodin

Peter Dowben Publications

Molecular bromine dissociatively adsorbs to form a chemisorbed overlayer on Ni(100). The bromine induced 4px,y and 4pz orbitals have been identified at Γ̅ with binding energies of 6.6 ± 0.2 eV and 5.3 ± 0.2 eV below the Fermi energy, respectively. The relative ionization cross-section variations of the two bromine levels 4px and 4pz are observed to differ with changing photon energy.

Go to article

Segregation Of Copper To The Surface Of Copper-Nickel Alloys, Peter A. Dowben Dec 1984

Segregation Of Copper To The Surface Of Copper-Nickel Alloys, Peter A. Dowben

Peter Dowben Publications

Copper segregation profiles at the surfaces of Cu17Ni83(111) and Cu17Ni83(100) have been calculated by a semiempirical procedure based upon previously published data. These profiles indicate that surface enrichment of copper is not limited only to the topmost layer but occurs for several layers away from the surface as well. A comparison of the calculated segregation profiles based upon the experimental results for the (100) and (111) surfaces of Cu17Ni83 do not agree with predictions based upon thermodynamic models of segregation.

Go to article

Surface-Wave-Induced Interference Effects In Angle-Resolved Photoemission, Peter A. Dowben, D. Heskett, E.W. Plummer, Y. Sakisaka, T.N. Rhodin, Cyrus Umrigar Oct 1984

Surface-Wave-Induced Interference Effects In Angle-Resolved Photoemission, Peter A. Dowben, D. Heskett, E.W. Plummer, Y. Sakisaka, T.N. Rhodin, Cyrus Umrigar

Peter Dowben Publications

New features are observed in normal-emission photoelectron spectra from Ni(100) in a narrow range of photon energies around 25 eV. These features are inconsistent with either direct transitions from the bulk or emission from occupied surface states or resonances. We suggest that they are a consequence of interference between the ordinary direct transition emitting an electron in the normal direction and the excitation from the same initial state into a final state that would normally be emitted from the surface at Γ― in the second surface Brillouin zone, but at this energy is trapped in a surface wave.

Go to article

Ammonia Adsorption And Decomposition On A Ni(Ll0) Surface, M. Grunze, M. Golze, R.K. Driscoll, Peter A. Dowben Mar 1981

Ammonia Adsorption And Decomposition On A Ni(Ll0) Surface, M. Grunze, M. Golze, R.K. Driscoll, Peter A. Dowben

Peter Dowben Publications

We report UPS/XPS results for ammonia adsorption and decomposition on a Ni(1 10)-surface. At T < 130 K molecular adsorption of NH 3 is observed to proceed with an initial sticking coefficient of s 0-0.1. Increasing the temperature of the nickel surface above 150 K results in partial dissociation of the adsorbed NH 3 molecules. The intermediate species are tentatively identified by their photoelectron spectra as NH-fragments. At temperatures above 350 K only atomic nitrogen is observed to populate the surface after NH 3-exposures. Our data show a similar reactivity of the Ni(ll0) surface in the NH 3-decomposition reaction as found on iron-single crystal …

Go to article

First Prev