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University of Nebraska - Lincoln

Peter Dowben Publications

Articles 241 - 270 of 284

Full-Text Articles in Physics

Multiplet Fine Structure In The Photoemission Of The Gadolinium And Terbium 5p Levels, B.T. Thole, X.D. Wang, B.N. Harmon, Dongqi Li, Peter A. Dowben Apr 1993

Multiplet Fine Structure In The Photoemission Of The Gadolinium And Terbium 5p Levels, B.T. Thole, X.D. Wang, B.N. Harmon, Dongqi Li, Peter A. Dowben

Peter Dowben Publications

Fine structure is observed in the photoemission of the gadolinium and terbium 5p levels. The 5p levels are split into multiplets due to spin-orbit splitting and to Coulomb and exchange interactions with the f shell. The calculated theoretical spectra are in good agreement with the experimental results.

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Characterization Of Boron Carbide Thin Films Fabricated By Plasma Enhanced Chemical Vapor Deposition From Boranes, Sunwoo Lee, John Mazurowski, G. Ramseyer, Peter A. Dowben Nov 1992

Characterization Of Boron Carbide Thin Films Fabricated By Plasma Enhanced Chemical Vapor Deposition From Boranes, Sunwoo Lee, John Mazurowski, G. Ramseyer, Peter A. Dowben

Peter Dowben Publications

We have fabricated boron carbide thin films on Si(111) and other substrates by plasma-enhanced chemical-vapor deposition (PECVD). The PECVD of boron carbides from nido-cage boranes, specially nido-pentaborane(9) (B5H9), and methane ( CH4) is demonstrated. The band gap is closely correlated with the boron to carbon ratio and can range from 0.77 to 1.80 eV and is consistent with the thermal activation barrier of 1.25 eV for conductivity. We have made boron carbide by PECVD from pentaborane and methane that is sufficiently isotropic to obtain resistivities as large as 1010 Ω cm …

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Structures Of Selected Boranes And Carboranes, Sunwoo Lee, Peter A. Dowben, A.T. Wen, A.P. Hitchcock, John A. Glass Jr., James T. Spencer Jul 1992

Structures Of Selected Boranes And Carboranes, Sunwoo Lee, Peter A. Dowben, A.T. Wen, A.P. Hitchcock, John A. Glass Jr., James T. Spencer

Peter Dowben Publications

Nido-pentaborane(9) (B5H9), 1, nido-2,3-diethyl-2,3-dicarbahexaborane(8)[( C2H5)2C2B4H6], 2, nido-decaborane (14) (B10H14), 3, closo- 1,2-dicarbadodecaborane(12) (H2C2B10H10), 4, can be used as possible source compounds for boron and boron carbide thin film deposition. Inner shell electron energy-loss spectroscopy (ISEELS) studies of the boron Is and carbon Is core excitations of gas phase species have been undertaken so as to characterize these molecular precursors at solid surfaces. The near edge structure of ISEELS provides a good "fingerprint" …

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Electronic Structure Of Borane Cage Molecules Adsorbed On Si(111), Sunwoo Lee, Dongqi Li, Sophie M. Cendrowski-Guillaume, Peter A. Dowben, F. Keith Perkins, S.P. Frigo, R.A. Rosenberg Jul 1992

Electronic Structure Of Borane Cage Molecules Adsorbed On Si(111), Sunwoo Lee, Dongqi Li, Sophie M. Cendrowski-Guillaume, Peter A. Dowben, F. Keith Perkins, S.P. Frigo, R.A. Rosenberg

Peter Dowben Publications

We compare the valence band photoemission resulting from molecular adsorption of nido-decaborane(14) (B10H14) and nido-2,3-diethyl-2,3-dicarbahexaborane on Si(111) at 100 K. The relative shift of the apparent valence band edge with increasing molecular coverage is consistent with the relative energy difference in the highest occupied molecular orbital for these two molecules as inferred from modified neglect of differential overlap calculations. The results suggest that the screening is very similar, despite the very different molecular structures of these two nido cage molecules.

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Evidence For The Formation Of Metallic Mercury Overlayers On Si(111), Dongqi Li, Jiandi Zhang, Sunwoo Lee, Peter A. Dowben May 1992

Evidence For The Formation Of Metallic Mercury Overlayers On Si(111), Dongqi Li, Jiandi Zhang, Sunwoo Lee, Peter A. Dowben

Peter Dowben Publications

A strongly chemisorbed Hg species is observed following the adsorption of Hg on Si(111) at 110 K. This strongly chemisorbed Hg species and subsequently weakly chemisorbed Hg species are observed to be metallic in the photoemission final state as determined by resonant photoemission and the reduction of photovoltaic charging. We postulate that the strongly chemisorbed Hg species on Si(111) is more metallic at dilute coverages than Hg adsorbed on Cu(100).

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Selective Area, Synchrotron Radiation Induced, Delta Doping Of Silicon, R.A. Rosenberg, S.P. Frigo, Sunwoo Lee, Peter A. Dowben May 1992

Selective Area, Synchrotron Radiation Induced, Delta Doping Of Silicon, R.A. Rosenberg, S.P. Frigo, Sunwoo Lee, Peter A. Dowben

Peter Dowben Publications

We have used broadband synchrotron radiation to induce selective area surface doping of boron into silicon. The source of the boron was nido-decaborane (B10H14) adsorbed on Si(111) at 100 K. Irradiation caused decomposition of the adsorbed molecule which lead to an enhanced concentration of free boron in the irradiated area. Using Si 2p core level photoelectron spectroscopy, the surface chemical composition and Fermi level position in both the irradiated and unirradiated regions were determined. The downward movement of the Fermi level was greater in the irradiated region than in the unirradiated region, and greater …

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Multiplet Fine Structure Of The Gd And Tb 5p Levels, Dongqi Li, Peter A. Dowben, M. Onellion May 1992

Multiplet Fine Structure Of The Gd And Tb 5p Levels, Dongqi Li, Peter A. Dowben, M. Onellion

Peter Dowben Publications

Fine structure is observed in the photoemission of Gd and Tb 5p levels as a result of multiplet splitting. These splittings are the consequence of different J final states that occur as a result of interactions with partly filled 4f and/or 5d levels.

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Demonstrating The Utility Of Boron Based Precursor Molecules For Selective Area Deposition In A Scanning Tunneling Microscope, F. Keith Perkins, M. Onellion, Sunwoo Lee, Peter A. Dowben May 1992

Demonstrating The Utility Of Boron Based Precursor Molecules For Selective Area Deposition In A Scanning Tunneling Microscope, F. Keith Perkins, M. Onellion, Sunwoo Lee, Peter A. Dowben

Peter Dowben Publications

The scanning tunneling microscope (STM) can be used to selectively deposit material from a gaseous precursor compound. Ultra-small (less than a 100 nm across) spatial dimensions for selective area deposition may be achieved by this means. In this paper we outline a scheme for selecting and designing main group cluster compounds and organometallics for this type of selective area deposition using nido-decaborane(l4) as an example.

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Temperature-Dependent Electronic Structure In A Localized-Magnetic-Moment System: Gadolinium, Dongqi Li, Jiandi Zhang, Peter A. Dowben, M. Onellion Apr 1992

Temperature-Dependent Electronic Structure In A Localized-Magnetic-Moment System: Gadolinium, Dongqi Li, Jiandi Zhang, Peter A. Dowben, M. Onellion

Peter Dowben Publications

At normal emission, the bulklike band in gadolinium overlayers on W(110) shifts toward EF from 1.64 eV at 310 K to 1.43 eV at 230 K in photoemission. This is accompanied by an increase of the feature width from 0.8 eV at 320 K to 1.1 eV at 230 K. The surface-state binding energy remains unchanged, though the width increases significantly with increasing temperature. The different effects of temperature upon the photoemission results obtained for the bulklike and surface states are interpreted as magnetic-order-induced band movement and spin mixing, respectively, and are discussed in the light of a quasiparticle theory. …

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Three-Dimensional Structure Of The Ordered Phases Of Hg On Cu(001), Wei Li, Jingsu Lin, M. Karimi, Peter A. Dowben, G. Vidali Feb 1992

Three-Dimensional Structure Of The Ordered Phases Of Hg On Cu(001), Wei Li, Jingsu Lin, M. Karimi, Peter A. Dowben, G. Vidali

Peter Dowben Publications

The structures of ordered phases following adsorption of mercury on Cu(001) have been identified using helium-beam scattering and low-energy electron diffraction. We found that three of the four observed ordered submonolayer phases are high-order commensurate phases. The three-dimensional structure of these phases brought about by a periodic variation of the height of the Hg atoms above the Cu(001) plane has been measured. Furthermore, from a combined analysis of helium-beam scattering and angle-resolved photoemission data for a low-density Hg ordered overlayer, we deduce and quantify the departure from the atomic electron distribution of Hg due to adsorption. A model to analyze …

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Development Of The Gd(0001) Band Structure With Film Thickness, Dongqi Li, W. Hutchings, Peter A. Dowben, Rong-Tzong Wu, C. Hwang, M. Onellion, A.B. Andrews, J.L. Erskine Nov 1991

Development Of The Gd(0001) Band Structure With Film Thickness, Dongqi Li, W. Hutchings, Peter A. Dowben, Rong-Tzong Wu, C. Hwang, M. Onellion, A.B. Andrews, J.L. Erskine

Peter Dowben Publications

By growing gadolinium films on W(110), it has been possible to observe the development of the Gd(0001) band structure with increasing film thickness. The changes in the 5d bands as a result of exposure to oxygen or the development of the valence-band structure with increasing film thickness lead to changes in the 5p multiplet oscillator strengths. These changes are a result of the influence of the band structure upon the final-state effects that give rise to such multiplet structures. This study provides conclusive evidence that there is a 5d contribution to the shallow 5p multiplet photoemission …

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Fabricating Magnetic Co-Ni-C Thin-Film Alloys By Organometallic Chemical Vapor Deposition, Yoon-Gi Kim, Dongjin Byun, C. Hutchings, Peter A. Dowben, H. Hejase, K. Schröder Nov 1991

Fabricating Magnetic Co-Ni-C Thin-Film Alloys By Organometallic Chemical Vapor Deposition, Yoon-Gi Kim, Dongjin Byun, C. Hutchings, Peter A. Dowben, H. Hejase, K. Schröder

Peter Dowben Publications

We have deposited CoxNiy-C films with a variety of compositions to verify dependence of the saturation magnetization on the composition. These experiments suggest that we can produce CoxNiy-C films with a variety of magnetic properties. The CoxNiy-C films were fabricated by ultraviolet decomposition of cobaltocene and nickelocene. We demonstrated that the photolytic decomposition of these metallocenes produces cyclopentadienyl (C5H5) species, consistent with recent studies of the energetics of the ligand metal bonds.

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Probing The Metal-Nonmetal Transition In Thin Metal Overlayers Using Resonant Photoemission, Peter A. Dowben, D. Lagraffe, Dongqi Li, G. Vidali, L. Zhang, L. Dottl, M. Onellion May 1991

Probing The Metal-Nonmetal Transition In Thin Metal Overlayers Using Resonant Photoemission, Peter A. Dowben, D. Lagraffe, Dongqi Li, G. Vidali, L. Zhang, L. Dottl, M. Onellion

Peter Dowben Publications

We have studied one and two monolayers of barium on Ni(111) and of mercury on Cu(100). Using resonant photoemission, we have found core excited electrons become delocalized with increasing barium coverage. Similarly, upon formation of the mercury bilayer (as determined by low-energy electron diffraction and by atom-beam scattering), there is a substantial increase in the screening of the photohole. A transition of the electronic structure akin to a metal-nonmetal (metal-insulator) transition is apparent in these final-state effects. The band structure for Hg is similar to the band structure expected for a free-standing film with a free-electron sd band. The delocalization …

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Novel Methods For Deposition Of Boron Carbide Films, J. Mazurowski, S. Baral-Tosh, G. Ramseyer, J.T. Spencer, Yoon-Gi Kim, Peter A. Dowben May 1991

Novel Methods For Deposition Of Boron Carbide Films, J. Mazurowski, S. Baral-Tosh, G. Ramseyer, J.T. Spencer, Yoon-Gi Kim, Peter A. Dowben

Peter Dowben Publications

By combining pentaborane (B5H9) and decarborane (B10H14) with methane in a plasma reactor, a variety of boron-carbides can be made over a wide range of compositions. The resulting thin films have uniform composition and appear to be polycrystalline.

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The Deposition Of Nickel Boride Thin Films By Borane And Metallaborane Cluster Compounds, John A. Glass Jr., Shreyas Kher, Yoon-Gi Kim, Peter A. Dowben, James T. Spencer May 1991

The Deposition Of Nickel Boride Thin Films By Borane And Metallaborane Cluster Compounds, John A. Glass Jr., Shreyas Kher, Yoon-Gi Kim, Peter A. Dowben, James T. Spencer

Peter Dowben Publications

The deposition of high purity and controlled stoichiometry metal boride thin-film materials has recently received considerable interest. Borane clusters and their corresponding metal complexes are currently Wig investigated in our laboratories for their utility as unique source materials for the formation of metallic boride thin films by MOCVD. Variable composition nickel boride thin films ranging from 0.1 micron to several microns have been prepared. These new materials have been characterized by SEM, AES and XES. The magnetic properties of these new films have been investigated with torque magnetometry and magneto-optic Kerr effect magnetometry.

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Thermal Desorption Of Hg Monolayers From Cu(100), Y.J. Kime, Jiandi Zhang, Peter A. Dowben May 1991

Thermal Desorption Of Hg Monolayers From Cu(100), Y.J. Kime, Jiandi Zhang, Peter A. Dowben

Peter Dowben Publications

A two dimensional phase transition from one adlayer structure to another is an inherent part of the thermal desorption of one monolayer of Hg on Cu(100). The energetics of this phase transition have been studied using thermal desorption spectroscopy (TDS). The TDS spectra reflect the coexistence of the two structural phases for a range of Hg exposures. The TDS spectra have been analyzed within a Polanyi-Wigner framework modified to account for the phase transition.

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Synchrotron-Radiation-Induced Deposition Of Boron And Boron Carbide Films From Boranes And Carboranes: Decaborane, F. Keith Perkins, R.A. Rosenberg, Sunwoo Lee, Peter A. Dowben Apr 1991

Synchrotron-Radiation-Induced Deposition Of Boron And Boron Carbide Films From Boranes And Carboranes: Decaborane, F. Keith Perkins, R.A. Rosenberg, Sunwoo Lee, Peter A. Dowben

Peter Dowben Publications

Boron has been deposited successfully on Si(111) from the synchrotron-radiation-induced decomposition of decaborane (14), i.e., B10H14. The rate of deposition is limited by the adsorption rate of decaborane (14) on the surface. In addition there is some indication that there is an activation barrier to dissociative adsorption. The synchrotron-radiation- induced growth rate of boron thin films from decaborane (14) is linear with coverage for a large range of thickness, suggesting a constant sticking coefficient for decaborane adsorption at room temperature.

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Selective Area Deposition Of Boron On Si(111) Induced By Synchrotron Radiation, R.A. Rosenberg, F.K. Perkins, D.C. Mancini, G.R. Harp, B.P. Tonner, S. Lee, Peter A. Dowben Feb 1991

Selective Area Deposition Of Boron On Si(111) Induced By Synchrotron Radiation, R.A. Rosenberg, F.K. Perkins, D.C. Mancini, G.R. Harp, B.P. Tonner, S. Lee, Peter A. Dowben

Peter Dowben Publications

We have performed the first deposition of boron on Si(111) induced by broadband synchrotron radiation (SR). Contamination-free thin films were grown at room temperature using decaborane (B10H14) as the source gas. After deposition the films were examined using photoelectron microscopy, which showed that film growth was limited to the region illuminated by SR. The temperature of the substrate rose less than 10 K. These results indicate that gas-phase excitations are not important and that the films are deposited by a nonthermal, photoinduced mechanism. Masked exposures demonstrate the potential of this technique for patterned deposition.

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Substrate-Induced Magnetic Ordering Of Rare-Earth Overlayers, Peter A. Dowben, D. Lagraffe, Dongqi Li, A. Miller, Ling Zhang, L. Dottl, M. Onellion Feb 1991

Substrate-Induced Magnetic Ordering Of Rare-Earth Overlayers, Peter A. Dowben, D. Lagraffe, Dongqi Li, A. Miller, Ling Zhang, L. Dottl, M. Onellion

Peter Dowben Publications

We have studied the magnetic ordering of terbium overlayers on Cu(100) and Ni(111), using angle-resolved photoemission. The 5p3/2 to 5p1/2 shallow-core-level branching ratios in different photoemission geometries provide a measure of the magnetic ordering in rare-earth-metal overlayers as a result of final-state effects in photoemission. We find that ferromagnetic substrates order paramagnetic terbium overlayers. This induced magnetic ordering is not a crystal-field effect and can be modeled by Ginzburg-Landau theory. Application of Ginzburg-Landau theory to our results suggests that the correlation length of paramagnetic terbium κ-1 is between 2.5 and 3.5 Å. Reversible increases in …

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Laser Cvd And Plasma Cvd Of Cro2 Films And Cobalt Doped Cro2 Films Using Organometallic Precursors, Peter A. Dowben, Marshall Onellion Dec 1990

Laser Cvd And Plasma Cvd Of Cro2 Films And Cobalt Doped Cro2 Films Using Organometallic Precursors, Peter A. Dowben, Marshall Onellion

Peter Dowben Publications

Chromium dioxide is deposited as a ferromagnetic layer onto selected portions of a substrate or over the entire substrate. Chromium hexacarbonyl vapor is introduced into a vacuum deposition chamber at e.g. 10 milliTorr and oxygen is introduced at e.g. 15 to 100 milliTorr. A UV laser beam is focused onto the substrate to form the CrO2 layer photolytically. The CrO2 layer can also be deposited by RF plasma deposition. This technique can also be employed for depositing MoC2, WC2, Mo2φ3, MoO2 or WO2. Magnetic recording or memory devices are …

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Synchrotron Radiation Induced Chemical Vapor Deposition Of Thin Films From Metal Hexacarbonyls*, Derrick C. Mancini, Shikha Varma, John K. Simons, Richard A. Rosenberg, Peter A. Dowben Nov 1990

Synchrotron Radiation Induced Chemical Vapor Deposition Of Thin Films From Metal Hexacarbonyls*, Derrick C. Mancini, Shikha Varma, John K. Simons, Richard A. Rosenberg, Peter A. Dowben

Peter Dowben Publications

We have studied the initial stages of synchrotron radiation [SR] induced chemical vapor deposition [CVD] of metal-containing thin films from metal hexacarbonyl gases. We have measured the dependence of the initial deposition rate upon gas pressure at room temperature. Substrates were exposed to SR for single fills of the electron storage ring at constant pressure of Mo(CO)6, Cr(CO)6, or W(CO) 6 gas. Deposition was monitored in situ by Auger electron spectroscopy using the SW as the excitation source. The presence of metal, carbon, and oxygen in the deposited films was observed, and the results are consistent …

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Deposition Of Boron-Containing Films From Decaborane, James T. Spencer, Peter A. Dowben, Yoon G. Kim Sep 1990

Deposition Of Boron-Containing Films From Decaborane, James T. Spencer, Peter A. Dowben, Yoon G. Kim

Peter Dowben Publications

Depopsition of a boron nitride film is carried out by introducing decaborane and dry nitrogen or ammonia into a plasma-assisted chemical vapor deposition chamber. The nitrogen or ammonia partial pressure should provide an excess over the decarborane pressures for example 200 milliTorr of N2 or NH3 and 50 MilliTorr of B10H14. Other film layers can also be produced starting from decaborane.

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Fabrication Of Ferromagnetic And Antiferromagnetic Chromium Oxides By Organometallic Chemical Vapor Deposition, Peter A. Dowben, Yoon Gi Kim, S. Baral-Tosh, G.O. Ramseyer, Chanyong Hwang, M. Onellion May 1990

Fabrication Of Ferromagnetic And Antiferromagnetic Chromium Oxides By Organometallic Chemical Vapor Deposition, Peter A. Dowben, Yoon Gi Kim, S. Baral-Tosh, G.O. Ramseyer, Chanyong Hwang, M. Onellion

Peter Dowben Publications

We have been able to fabricate CrO2 and Cr2O3 from ultraviolet photolytic and plasma-assisted decomposition of Cr(CO) 6 in an oxygen carrier gas. The composition of these films is uniform in composition and contains little contamination. Using magneto-optic Kerr effect measurements, we have been able to demonstrate that the CrO2 films are ferromagnetic.

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The Chemistry Of The Gadolinium-Nickel Interface, D. Lagraffe, Peter A. Dowben, M. Onellion May 1990

The Chemistry Of The Gadolinium-Nickel Interface, D. Lagraffe, Peter A. Dowben, M. Onellion

Peter Dowben Publications

Gadolinium overlayers on Ni(111) have been studied by angle resolved photoemission, angle resolved AES, LEED, and RHEEB. We have observed pronounced interdiffusion of nickel with the gadolinium overlayer at temperatures as low as 150 K. This is in marked contrast with gadolinium overlayers on Cu(108) where substantial interdiffusion is not observed until 360 K, but is consistent with studies of ytterbium on nickel. [A. Nilsson, B Eriksson, N. Martenssom, J. N. Andersen, and J. Onsgaard, Phys. Rev. B 38,10357, ( 1988) and I. Chorkendorff, K. Onsgaard, J. Schmidt-May and R. Nyholm, Surf. Sci. 160, 587, (1985) .] There is a …

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Ordering Of Metal Overlayers On Metal Substrates Studied Using Atom Beam Scattering, G. Vidali, C.W. Hutchings, Peter A. Dowben, M. Karimi, C. Moses, M. Foresti May 1990

Ordering Of Metal Overlayers On Metal Substrates Studied Using Atom Beam Scattering, G. Vidali, C.W. Hutchings, Peter A. Dowben, M. Karimi, C. Moses, M. Foresti

Peter Dowben Publications

We will illustrate how atom beam scattering (ABS) can be used to study the growth and ordering of adsorption of Hg on Cu(001). At low coverage (less than 2% of a monolayer), we obtain that the scattering cross section of He with (adsorbed) Hg is about 50 Å2. We find that mercury forms two stable phases on Cu(001) in the temperature range between 200 and 330 K, a c (2 x 2) and a high density c (4 x 4) phase. From ABS diffraction data, we can deduce the corrugation of the surface electron charge density of the …

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The Effect Of Lateral Interactions On The Thermal Desorption Of N2 From Ni(100), Shikha Varma, Peter A. Dowben May 1990

The Effect Of Lateral Interactions On The Thermal Desorption Of N2 From Ni(100), Shikha Varma, Peter A. Dowben

Peter Dowben Publications

We have investigated the desorption of N2 from Ni(100) using thermal desorption spectroscopy (TDS). A modified Polanyi-Wigner equation has been used to obtain the desorption energy and the preexponential factor, both of which depend on the coverage of the adsorbate. We show that there is a large lateral interaction among the adlayer molecules when N2 goes down as ordered c (2 X 2) on Ni. In addition, the overlayer ordering, in the thermal desorption process, is observed to affect the thermal desorption spectra.

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Selective Area Deposition Of Conducting Palladium Films On Polyimide Resins, Yoon-Gi Kim, S. Bialy, R.W. Miller, J.T. Spencer, Peter A. Dowben, Saswati Datta May 1990

Selective Area Deposition Of Conducting Palladium Films On Polyimide Resins, Yoon-Gi Kim, S. Bialy, R.W. Miller, J.T. Spencer, Peter A. Dowben, Saswati Datta

Peter Dowben Publications

We have demonstrated that the selective area deposition of palladium on polyimide substrates i s possible through the U.V. photolysis of (π - a l l y 1) (π –cyclopentadieny1) palladium. This photolytic deposition process did not result in any apparent damage to either the Ultem 1000 (polyetherimide) or Kapton substrates (polyimide substrates). The resistivity of the palladium films (< 0.1 um) suggests that the films are porous.

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Magnetic Ordering Of Tb Overlayers On Ni(Ll1), D. Lagraffe, A. Miller, Peter A. Dowben, M. Onellion May 1990

Magnetic Ordering Of Tb Overlayers On Ni(Ll1), D. Lagraffe, A. Miller, Peter A. Dowben, M. Onellion

Peter Dowben Publications

The 5p3/2 to 5p1/2 shallow core level branching ratios in different - photoemission geometries provide a measure of the magnetic ordering in rare earth overlayers as a result of final state effects in photoemission. This 5p level anisotropy can be used to probe magnetic ordering across the Tb Curie temperature as well as magnetic ordering induced by a ferromagnetic substrate in Results are shown for paramagnetic Tb overlayers on Ni(111). The Ginsberg-Landau theory can be used to accurately model terbium thin films for T>Tc.

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Thermochemistry Of The Gadolinium-Copper Interface, D. Lagraffe, Peter A. Dowben, M. Onellion Aug 1989

Thermochemistry Of The Gadolinium-Copper Interface, D. Lagraffe, Peter A. Dowben, M. Onellion

Peter Dowben Publications

We have characterized the thermochemistry of the gadolinium-copper interface using valence-band photoemission. We find that the copper substrate binds strongly with the gadolinium overlayer, based upon valence-band binding-energy shifts that occur with increasing gadolinium coverages on Cu(100). The net potential for copper at the interface is 3.82 eV/atom which is some 0.51 eV/atom greater than the heat of sublimation for copper. The strong bonds formed between copper and gadolinium provide a thermochemical driving force for copper gadolinium-alloy formation. We observed a surface-to-bulk core-level shift for gadolinium of 0.3–0.4 eV. We also observed a Cu 3d binding-energy increase of 0.73 …

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Magnetic Ordering Of Thin Gd Overlayers, D. Lagraffe, Peter A. Dowben, M. Onellion Jul 1989

Magnetic Ordering Of Thin Gd Overlayers, D. Lagraffe, Peter A. Dowben, M. Onellion

Peter Dowben Publications

1–6-monolayer-thick films of Gd have been studied with use of synchrotron-radiation photoemission. A method is described that utilizes the linear light polarization to obtain information about the overlayer magnetization. The method is complementary to electron-spin-polarization techniques. The thinner Gd overlayers exhibit a local magnetization component along the surface normal that decreases for thicker overlayers. The Gd films exhibit a 5d exchange splitting that changes from approximately 1.1 to 0.6 eV as the overlayer thickness increases.

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