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Full-Text Articles in Physics
Characterization Of Boron Carbide Thin Films Fabricated By Plasma Enhanced Chemical Vapor Deposition From Boranes, Sunwoo Lee, John Mazurowski, G. Ramseyer, Peter A. Dowben
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 …
Structures Of Selected Boranes And Carboranes, Sunwoo Lee, Peter A. Dowben, A.T. Wen, A.P. Hitchcock, John A. Glass Jr., James T. Spencer
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" …
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
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.
Evidence For The Formation Of Metallic Mercury Overlayers On Si(111), Dongqi Li, Jiandi Zhang, Sunwoo Lee, Peter A. Dowben
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).
Selective Area, Synchrotron Radiation Induced, Delta Doping Of Silicon, R.A. Rosenberg, S.P. Frigo, Sunwoo Lee, Peter A. Dowben
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 …
Multiplet Fine Structure Of The Gd And Tb 5p Levels, Dongqi Li, Peter A. Dowben, M. Onellion
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.
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
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.
Temperature-Dependent Electronic Structure In A Localized-Magnetic-Moment System: Gadolinium, Dongqi Li, Jiandi Zhang, Peter A. Dowben, M. Onellion
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. …
Three-Dimensional Structure Of The Ordered Phases Of Hg On Cu(001), Wei Li, Jingsu Lin, M. Karimi, Peter A. Dowben, G. Vidali
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 …