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Full-Text Articles in Physics

Spectrally Narrowed Edge Emission From Leaky Waveguide Modes In Organic Light-Emitting Diodes, Zhengqing Gan, Yun Tian, David W. Lynch, Ji-Hun Kang, Q-Han Park, Joseph Shinar Jan 2009

Spectrally Narrowed Edge Emission From Leaky Waveguide Modes In Organic Light-Emitting Diodes, Zhengqing Gan, Yun Tian, David W. Lynch, Ji-Hun Kang, Q-Han Park, Joseph Shinar

Physics and Astronomy Publications

A dramatic spectral line narrowing of the edge emission at room temperature from tris(quinolinolate) Al (Alq3), N,N′-diphenyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine (NPD), 4,4′-bis(2,2′-diphenyl-vinyl)-,1′-biphenyl (DPVBi), and some guest-host small molecular organic light-emitting diodes(OLEDs), fabricated on indium tin oxide (ITO)-coated glass, is described. In all but the DPVBi OLEDs, the narrowed emission band emerges above a threshold thickness of the emitting layer, and narrows down to a full width at half maximum of only 5–10 nm. The results demonstrate that this narrowed emission is due ...


Spectrally Narrowed Edge Emission From Organic Light-Emitting Diodes, Yun Tian, Zhengqing Gan, Zhaoqun Zhou, David W. Lynch, Joseph Shinar, Ji-Hun Kang, Q-Han Park Oct 2007

Spectrally Narrowed Edge Emission From Organic Light-Emitting Diodes, Yun Tian, Zhengqing Gan, Zhaoqun Zhou, David W. Lynch, Joseph Shinar, Ji-Hun Kang, Q-Han Park

Physics and Astronomy Publications

A dramatic spectrally narrowed edge emission (SNEE) from small molecular organic light-emitting diodes at room temperature, with a full width at half maximum of 5–10nm, is described. The results show that this emission is due to irregular waveguide modes that leak from the indium tin oxide anode to the glass substrate at a grazing angle. Measurements of variable stripe length devices exhibit an apparent weak optical gain, but there is no observable threshold bias associated with this SNEE. Hence this apparent “optical gain” is suspected to result from misalignment of the propagating leaky waveguide mode and the collecting optics.


Angle-Resolved Photoemission Study Of The Rare-Earth Intermetallic Compounds: Rni2ge2(R=Eu,Gd), Joong Mok Park, D. P. Brammeier, C. G. Olson, Paul C. Canfield, David W. Lynch Aug 2004

Angle-Resolved Photoemission Study Of The Rare-Earth Intermetallic Compounds: Rni2ge2(R=Eu,Gd), Joong Mok Park, D. P. Brammeier, C. G. Olson, Paul C. Canfield, David W. Lynch

Physics and Astronomy Publications

Experimental energy bands mapped from normal-emission photoelectron spectra of EuNi2Ge2 and GdNi2Ge2(001)surfaces show four photoemission features that disperse in both materials in good agreement with band calculations. Segments of the Fermi surfaces mapped by angle-resolved photoemission spectroscopy in the ΓXPZ plane of the Brillouin zones for both EuNi2Ge2 and GdNi2Ge2 are in good agreement with band calculations. This Fermi surface segment changes when one electron is added to EuNi2Ge2, corresponding to GdNi2Ge2, based on the rigid-band approximation.


Highly Directional Receiver And Source Antennas Using Photonic Band Gap Crystals, Rana Biswas, Gary L. Tuttle, Ekmel Ozbay, Burak Temelkuran, Mihail Sigalas, Kai-Ming Ho Jul 2003

Highly Directional Receiver And Source Antennas Using Photonic Band Gap Crystals, Rana Biswas, Gary L. Tuttle, Ekmel Ozbay, Burak Temelkuran, Mihail Sigalas, Kai-Ming Ho

Iowa State University Patents

A directional antenna made with photonic band gap structures has been presented. The directional antenna is formed with two photonic band gap structures oriented back to back and separated from each other by a distance to form a resonant cavity between the photonic band gap structures. An antenna element is placed in the resonant cavity. The resonant frequency of the cavity is tuned by adjusting the distance between the photonic band gap structures. The resonant cavity can be asymmetrical or symmetrical.


A New Spectrometer Using Multiple Gratings With A Two-Dimensional Charge-Coupled Diode Array Detector, Tao Han, Wei-Ming Ni, Peng Zhao, Hai-Yang You, Jian-Hu Jia, Song-You Wang, Liang-Yao Chen, David W. Lynch Jun 2003

A New Spectrometer Using Multiple Gratings With A Two-Dimensional Charge-Coupled Diode Array Detector, Tao Han, Wei-Ming Ni, Peng Zhao, Hai-Yang You, Jian-Hu Jia, Song-You Wang, Liang-Yao Chen, David W. Lynch

Physics and Astronomy Publications

A new spectrometer with no moving parts uses a two-dimensional Si-based charge-coupled diode (CCD) array detector and an integrated grating consisting of three subgratings. The effective spectral range imaged on the detector is magnified threefold. The digitized spectral image in the 200–1000 nm wavelength range can be measured quickly. The nonlinear relationship between CCD pixel position and wavelength is corrected with multiple polynomial functions in the calibration procedure, which fits the data using a mathematical pattern-analysis method. The instrument can be applied for rapid spectroscopicdata analyses in many types of photoelectronic experiments and routine testing.


Optical Properties And Electronic Structures Of Single Crystalline Ral3(R=Sc, Yb, And Lu), S. J. Lee, J. M. Park, Paul C. Canfield, David W. Lynch Feb 2003

Optical Properties And Electronic Structures Of Single Crystalline Ral3(R=Sc, Yb, And Lu), S. J. Lee, J. M. Park, Paul C. Canfield, David W. Lynch

Physics and Astronomy Publications

The optical conductivities of single crystals of ScAl3, LuAl3, and YbAl3 were measured by spectroscopic ellipsometry in the energy range of 1.5–5.5 eV. The conductivity spectra of all show peaks between 1.5 and 2.0 eV originating from interband transitions. Two additional peaks around at 2.9 and 4.2 eV are observed for ScAl3, and a weak shoulder is observed around at 2.8 eV for LuAl3. Band structure, density of states, and optical conductivity were calculated using the full-potential linear augmented plane wave method. The calculated conductivity spectrum for ScAl3 shows peaks around at ...


Optical Properties And Electronic Structure Of Mgausn, S. J. Lee, J. M. Park, T. A. Wiener, L. L. Miller, David W. Lynch Sep 2001

Optical Properties And Electronic Structure Of Mgausn, S. J. Lee, J. M. Park, T. A. Wiener, L. L. Miller, David W. Lynch

Physics and Astronomy Publications

The optical conductivity spectrum of single-crystal MgAuSn was measured by spectroscopic ellipsometry in the energy range 1.5–5.0 eV. The spectrum has a large peak at 2.9 eV and a small shoulder around 4.3 eV. The band structure, density of states, and interband contribution to the optical conductivity were calculated with the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation. The intraband contribution to the optical conductivity was added using the Drude response fitted to the experimental data. The total theoretical spectrum, including the intraband contribution, agrees well with experimental data.


Optical Properties Of Rni2b2c (R=Y,Tb,Er,Dy), S. J. Lee, B. K. Cho, Paul C. Canfield, David W. Lynch May 2001

Optical Properties Of Rni2b2c (R=Y,Tb,Er,Dy), S. J. Lee, B. K. Cho, Paul C. Canfield, David W. Lynch

Physics and Astronomy Publications

The optical properties of single crystals of RNi2B2C (R=Y,Tb,Er, and Dy) were measured between 1.7 and 5.2 eV at room temperature using a spectroscopic ellipsometer. The spectra for all compounds are similar and the peak positions appear in a similar energy region. The similarity of the spectra of RNi2B2C (R=Tb,Er,Dy) to that of YNi2B2C indicates that the rare-earth 4f states are not actively involved in the optical transitions.


No Well-Defined Remnant Fermi Surface In Sr2cuo2cl2, S. Haffner, D. P. Brammeier, C. G. Olson, L. L. Miller, David W. Lynch Apr 2001

No Well-Defined Remnant Fermi Surface In Sr2cuo2cl2, S. Haffner, D. P. Brammeier, C. G. Olson, L. L. Miller, David W. Lynch

Physics and Astronomy Publications

In angle-resolved photoelectron spectra of the antiferromagnetic insulators Ca2CuO2Cl2 and Sr2CuO2Cl2, a sharp drop of the spectral intensity of the lowest-lying band is observed along a line in k space equivalent to the Fermi surface of the optimally doped high-temperature superconductors. This was interpreted as a signature of the existence of a remnant Fermi surface in the insulating phase of the high-temperature superconductors. In this paper it is shown that the drop of the spectral intensity is not related to the spectral function but is a consequence of the electron-photon matrix element.


Optical And Magneto-Optical Investigation On Electronic Structure Of Ordered Ferromagnetic Fe3pt, K. J. Kim, S. J. Lee, T. A. Wiener, David W. Lynch Jan 2001

Optical And Magneto-Optical Investigation On Electronic Structure Of Ordered Ferromagnetic Fe3pt, K. J. Kim, S. J. Lee, T. A. Wiener, David W. Lynch

Physics and Astronomy Publications

The optical and magneto-opticalproperties of ordered Fe3Pt have been investigated by spectroscopicellipsometry and magneto-opticalKerrspectroscopy. The diagonal component of the optical conductivity tensor of the compound exhibits a broad absorption peak at about 2 eV, which is shifted by about 0.5 eV to lower energies from the corresponding one in pure bcc Fe. The Kerr angle spectrum of the compound disperses quite similarly in both spectral trend and magnitude to that of pure Fe below 3.5 eV but differently above it. The lower-energy shift of the 2-eV-absorption structure of the compound is interpreted as due to the shift of ...


Fe−3s Core-Level Splitting And Local Magnetism In Fe2val, Ye Feng, M. V. Dobrotvorska, James W. Anderegg, C. G. Olson, David W. Lynch Jan 2001

Fe−3s Core-Level Splitting And Local Magnetism In Fe2val, Ye Feng, M. V. Dobrotvorska, James W. Anderegg, C. G. Olson, David W. Lynch

Physics and Astronomy Publications

X-ray and soft x-ray photoelectron spectra were taken on Fe2VAl samples. The Fe−3s spectra show a shoulder on the higher binding energy side of the main peak, split by ≈4.7 eV. Based on current understanding of core-level multiplet splitting in transition-metal compounds, we believe this is direct evidence of a local moment in Fe2VAl.


Optical And Magneto-Optical Properties And Electronic Structures Of Single-Crystalline Ral2 (R=Y, La, Ce, Pr, And Lu), R. J. Lange, S. J. Lee, K. J. Kim, Paul C. Canfield, David W. Lynch Dec 2000

Optical And Magneto-Optical Properties And Electronic Structures Of Single-Crystalline Ral2 (R=Y, La, Ce, Pr, And Lu), R. J. Lange, S. J. Lee, K. J. Kim, Paul C. Canfield, David W. Lynch

Physics and Astronomy Publications

The diagonal optical conductivity spectra of single crystals of RAl2 (R=Y, La, Ce, Pr, and Lu) were measured at room temperature by spectroscopic ellipsometry in the 1.5–5.6−eV range. All the compounds exhibit two strong interband absorption peaks at about 1.8 and 3.6 eV for YAl2 and LuAl2, and at about 2.0 and 3.0 eV for LaAl2, CeAl2, and PrAl2. Such differences in the second peak position appear in the theoretical optical conductivity spectra calculated from their band structures obtained by the tight-binding linear-muffin-tin-orbitals method. Most of the contributions to the two ...


Observation Of A Metamagnetic Phase Transition In An Itinerant 4f System Via The Magneto-Optic Kerr Effect: Ce(Fe1−Xcox)2, R. J. Lange, I. R. Fisher, Paul C. Canfield, Vladimir P. Antropov, S. J. Lee, Bruce N. Harmon, David W. Lynch Sep 2000

Observation Of A Metamagnetic Phase Transition In An Itinerant 4f System Via The Magneto-Optic Kerr Effect: Ce(Fe1−Xcox)2, R. J. Lange, I. R. Fisher, Paul C. Canfield, Vladimir P. Antropov, S. J. Lee, Bruce N. Harmon, David W. Lynch

Physics and Astronomy Publications

The optical and magneto-optical properties of single crystals of YFe2, CeFe2, and Ce(Fe1−xCox)2 (x≃0.1) were measured between 1.4 and 5.0 eV using a rotating-analyzer ellipsometer and a normal-incidence polar Kerr spectrometer. The electronic structures and optical properties of YFe2 and CeFe2 were calculated using the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation. For YFe2 the calculations reproduce the experimental spectra. Alloying CeFe2 with small amounts of Co leads to an electronic instability which is evidenced by a low-temperature antiferromagnetic (AF) phase. The Kerr effect was measured in the AF and field-induced ...


Evidence For A Strong Impact Of The Electron-Photon Matrix Element On Angle-Resolved Photoelectron Spectra Of Layered Cuprate Compounds, S. Haffner, C. G. Olson, L. L. Miller, David W. Lynch Jun 2000

Evidence For A Strong Impact Of The Electron-Photon Matrix Element On Angle-Resolved Photoelectron Spectra Of Layered Cuprate Compounds, S. Haffner, C. G. Olson, L. L. Miller, David W. Lynch

Physics and Astronomy Publications

Little is known about the impact of the electron-photon matrix element on angle-resolved photoelectron spectra of layered cuprate compounds. Using the example of the model layered cuprate Sr2CuO2Cl2, we demonstrate that the electron-photon matrix element has a significant influence on energy distribution curves, rendering their interpretation as images of the spectral function nontrivial.


Optical And Magneto-Optical Properties Of Rfe2 (R=Gd,Tb,Ho,Lu) And Gdco2, S. J. Lee, R. J. Lange, Paul C. Canfield, Bruce N. Harmon, David W. Lynch Apr 2000

Optical And Magneto-Optical Properties Of Rfe2 (R=Gd,Tb,Ho,Lu) And Gdco2, S. J. Lee, R. J. Lange, Paul C. Canfield, Bruce N. Harmon, David W. Lynch

Physics and Astronomy Publications

The conductivity tensors of single crystals and polycrystals of RFe2 (R=Gd,Tb,Ho,Lu) and GdCo2 were determined in the visible and near UV ranges. The magneto-optical Kerr effect (MOKE) was studied at different temperatures and magnetic fields. The single-crystal data show more features and larger magnitudes in the MOKE spectrum than the polycrystalline data under the same experimental conditions. The theoretical optical conductivity tensors for these compounds were calculated using the tight-binding linear-muffin-tin orbital (TB-LMTO) method in the local spin-density approximation. The agreement between theory and experiment was poor except for LuFe2, in which the 4f shell is ...


Optical Properties And Electronic Structure Of Single Crystals Of Lual2 And Ybal2, S. J. Lee, S. Y. Hong, I. R. Fisher, Paul C. Canfield, Bruce N. Harmon, David W. Lynch Apr 2000

Optical Properties And Electronic Structure Of Single Crystals Of Lual2 And Ybal2, S. J. Lee, S. Y. Hong, I. R. Fisher, Paul C. Canfield, Bruce N. Harmon, David W. Lynch

Physics and Astronomy Publications

The optical conductivities of single crystals of LuAl2 and YbAl2 were measured by spectroscopic ellipsometry in the energy range of 1.4–5.5eV for LuAl2 and 1.4–5.2eV for YbAl2. The optical conductivity spectra of LuAl2 and YbAl2 show similar features except for a difference in magnitude. Both have peaks near 1.8–2.1eV and broad shoulders between 3.0 and 4.0eV. The shoulder is weaker in YbAl2. The band structure, density of states, and optical conductivity were calculated with the tight-binding linear muffin-tin orbital method in the atomic sphere approximation. The calculated optical conductivity ...


Evidence For Replicate 5p Core Levels In Photoelectron Spectra Of Eu Metal Due To Nonconstant Kinetic-Energy Resonant Auger Decay, S. Haffner, C. G. Olson, David W. Lynch Dec 1999

Evidence For Replicate 5p Core Levels In Photoelectron Spectra Of Eu Metal Due To Nonconstant Kinetic-Energy Resonant Auger Decay, S. Haffner, C. G. Olson, David W. Lynch

Physics and Astronomy Publications

Satellites on the low-binding-energy side of core-level photoelectron emission due to extra 4f screening are a well-known feature in the x-ray photoelectron spectra of valence fluctuation materials and rare-earth metals. A notable exception is Eu metal, where up to now no low-binding-energy satellite has been observed. In this paper we show that in Eu metal the 4d−4f resonance can decay via a resonant Auger decay, which is not a constant kinetic-energy feature due to a rapid change of the strength of 4f screening with excitation energy, establishing a low-binding-energy replica of the 5p core-level photoelectron emission.


Optical Properties And Electronic Structures Of B2 And B19′ Phases Of Equiatomic Ni-Ti Alloys, Joo Yull Rhee, Bruce N. Harmon, David W. Lynch Jan 1999

Optical Properties And Electronic Structures Of B2 And B19′ Phases Of Equiatomic Ni-Ti Alloys, Joo Yull Rhee, Bruce N. Harmon, David W. Lynch

Physics and Astronomy Publications

The dielectric functions of equiatomic Ni-Ti alloys were measured by spectroscopic ellipsometry in the energy range of 1.5–5.4 eV at ∼423 and at ∼25 K. The peak at ∼2.26 eV in the B19′ (monoclinic structure) optical conductivity spectrum has a slightly larger magnitude than in the B2 (cubic CsCl structure) phase, while the shoulder at ∼3.5 eVbecomes weaker and almost indiscernible upon martensitic transformation. A new structure develops at ∼2.85 eV in the B19′ phase; however, it is also very weak. The band structures and the optical conductivity were calculated in both phases using ...


Ellipsometric And Kerr-Effect Studies Of Pt3−X (X=Mn,Co), R. J. Lange, S. J. Lee, David W. Lynch, Paul C. Canfield, Bruce N. Harmon, S. Zollner Jul 1998

Ellipsometric And Kerr-Effect Studies Of Pt3−X (X=Mn,Co), R. J. Lange, S. J. Lee, David W. Lynch, Paul C. Canfield, Bruce N. Harmon, S. Zollner

Physics and Astronomy Publications

The conductivity tensor of polycrystalline Pt3X (X=Mn,Co) was determined between 1.6 and 5.2 eV. Samples were arc melted, mechanically polished, and annealed at 500°C for 1 h in Ar. The complex dielectric function was measured from 1.3 to 5.2 eV at room temperature with a rotating analyzer ellipsometer. The magneto-optic Kerr effect was studied between 10 and 293 K in magnetic fields up to 3 T. We used the tight-binding linear-muffin-tin-orbital method in the local spin-density approximation to determine the band structure, density of states, and optical conductivity. Including an empirical quasiparticle self-energy ...


Optical Properties And Electronic Structures Of Ni3al Alloys, Joo Yull Rhee, David W. Lynch, Bruce N. Harmon Feb 1997

Optical Properties And Electronic Structures Of Ni3al Alloys, Joo Yull Rhee, David W. Lynch, Bruce N. Harmon

Physics and Astronomy Publications

The dielectric functions of Ni3Al polycrystalline alloys were measured by spectroscopic ellipsometry in the energy range of 1.5–5.4 eV. The samples were Ni1−xAlx alloys with x=0.2625,0.2525,0.25,0.244, and 0.2359. One broad peak was observed in the optical-conductivity spectra around 4.4 eV. The band structures and the optical conductivity were calculated in the Au3Cu structure with the linearized-augmented-plane-wave method. By including both energy-dependent broadening and an approximate self-energy correction the calculated optical-conductivity spectrum gives quite good agreement with experiment. The calculation shows that the main contribution to the ...


Optical Properties And Electronic Structures Of Equiatomic Xti (X=Fe,Co,Andni) Alloys, Joo Yull Rhee, Bruce N. Harmon, David W. Lynch Dec 1996

Optical Properties And Electronic Structures Of Equiatomic Xti (X=Fe,Co,Andni) Alloys, Joo Yull Rhee, Bruce N. Harmon, David W. Lynch

Physics and Astronomy Publications

The dielectric functions of equiatomic XTi (X=Fe,Co,andNi) alloys in the B2 phase (cubic CsCl structure) were measured by spectroscopic ellipsometry in the energy range of 1.5-5.4 eV. The optical conductivity spectra show close resemblance to each other with a peak at 1.9-2.3 eV and another at 3.1-3.4 eV. Fine structures observed in previously reported measurements were not seen. The band structures and the optical conductivity spectra were calculated in the B2 phase using the linearized-augmented-plane-wave method with the local density approximation. The agreement between the measured and calculated spectra is markedly ...


Photoelectron Spectra Of An Al70pd21mn9 Quasicrystal And The Cubic Alloy Al60pd25mn15, Cynthia J. Jenks, S.-L. Chang, James W. Anderegg, Patricia A. Thiel, David W. Lynch Sep 1996

Photoelectron Spectra Of An Al70pd21mn9 Quasicrystal And The Cubic Alloy Al60pd25mn15, Cynthia J. Jenks, S.-L. Chang, James W. Anderegg, Patricia A. Thiel, David W. Lynch

Physics and Astronomy Publications

Photoelectron spectra of a fivefold quasicrystalline alloy Al70Pd21Mn9 and a related cubic alloy Al60Pd25Mn15 reveal two noteworthy features. The first is that the Pd 3d lines fall at binding energies which are 2.2 eV higher than in pure Pd. A similar shift is observed for Pd in other alloys. The second noteworthy feature is that the Mn 2p32 line is very sharp in the quasicrystal. Fitting the experimental peaks with a Doniach-Sunjic line shpae suggests that the position and density of Mn states near EF is very sensitive to the structural and/or chemical environment of Mn in the ...


Valence-Band Dispersion In Angle-Resolved Resonant Photoemission From Lasb, C. G. Olson, P. J. Benning, Michael Schmidt, David W. Lynch, Paul C. Canfield, David Michael Wieliczka May 1996

Valence-Band Dispersion In Angle-Resolved Resonant Photoemission From Lasb, C. G. Olson, P. J. Benning, Michael Schmidt, David W. Lynch, Paul C. Canfield, David Michael Wieliczka

Physics and Astronomy Publications

Angle-resolved photoemission spectra taken on single crystals of LaSb at the La 4d→4f resonance show dispersion of resonantly emitted valence-band electrons. This is the first direct demonstration that the Bloch component of valence states participates in resonant photoemission.


Electronic Band Dispersion And Pseudogap In Quasicrystals: Angular-Resolved Photoemission Studies On Icosahedral Al70pd21.5mn8.5, X. Wu, Stefan Walenty Kycia, C. G. Olson, P. J. Benning, Alan I. Goldman, David W. Lynch Dec 1995

Electronic Band Dispersion And Pseudogap In Quasicrystals: Angular-Resolved Photoemission Studies On Icosahedral Al70pd21.5mn8.5, X. Wu, Stefan Walenty Kycia, C. G. Olson, P. J. Benning, Alan I. Goldman, David W. Lynch

Physics and Astronomy Publications

Angular-resolved photoelectron spectra from the fivefold surface of single-grain icosahedral Al70Pd21.5Mn8.5 exhibit a quasiperiodic dispersion of 300 meV at 2.3 eV binding energy. Low energy electron diffraction studies confirm quasicrystalline order at the surface. A distinct pseudogap feature is observed with a density of states near the Fermi level decreasing as a square-root power law.


New Metastable Nonmetallic Phase Of Europium, C. G. Olson, X. Wu, Z.-L. Chen, David W. Lynch Feb 1995

New Metastable Nonmetallic Phase Of Europium, C. G. Olson, X. Wu, Z.-L. Chen, David W. Lynch

Physics and Astronomy Publications

Metastable, close-packed films of elemental, divalent Eu from about a half to several monolayers thick on several substrates were found to be nonmetallic. Photoemission showed no states within 1.4 eV of the Fermi level. Low energy electron diffraction studies of Eu films on Ta(110) showed a closepacked pattern with orientational epitaxy. With increased thickness this phase reverted to metallic bcc Eu with orientational epitaxy.


Optical Properties Of Fe-Rh Alloys, Joo Yull Rhee, David W. Lynch Jan 1995

Optical Properties Of Fe-Rh Alloys, Joo Yull Rhee, David W. Lynch

Physics and Astronomy Publications

The dielectric functions (ε̃) of FexRh1−x alloys with x=0.48, 0.5, and 0.54 were measured by spectroscopic ellipsometry in the energy range 1.5–5.4 eV. The optical properties do not change drastically as the antiferromagnetic (AF)-ferromagnetic (F) phase transition occurs.


Band Dispersion In C60(111): An Angle-Resolved Photoemission Study, P. J. Benning, C. G. Olson, David W. Lynch, J. H. Weaver Oct 1994

Band Dispersion In C60(111): An Angle-Resolved Photoemission Study, P. J. Benning, C. G. Olson, David W. Lynch, J. H. Weaver

Physics and Astronomy Publications

Angle-resolved photoemission studies of single-crystal C60(111) films grown on GeS(001) reveal changes in valence feature line shape with emission angle and photon energy that are indicative of band dispersion. For an excitation energy (hν) of 10 eV, normal emission spectra show four sharp structures within the ∼1.1-eV-wide valence feature derived from the second highest molecular orbital (HOMO-1) of C60. For hν=8.1 eV, the 1-eV-wide HOMO-derived feature exhibits changes with emission angle mainly due to dispersion of 0.6 eV in the unoccupied bands. The distribution of electronic states underlying HOMO and HOMO-1 indicates ...


Photoemission Study Of Ce-Catalyzed Oxidation Of W(110) And W(111), C. Gu, C. G. Olson, David W. Lynch Oct 1993

Photoemission Study Of Ce-Catalyzed Oxidation Of W(110) And W(111), C. Gu, C. G. Olson, David W. Lynch

Physics and Astronomy Publications

Different catalytic oxidation effects of Ce on W(110) and W(111) were observed with photo- emission spectroscopy. On Ce-covered W(110), the top W layer is quickly oxidized to a surface monoxide at room temperature. Oxidation is almost halted after the completion of one monolayer of WO. On Ce/W(111), instead of WO, WO3 grows on the surface under the same conditions. The monolayer suboxide formation found on Ce/W(110) and Ce/Ta(110) (as reported earlier) is a direct consequence of the most densely packed structure of the bcc (110) surfaces. The more effective oxidation promotion ...


Large Low-Energy Oscillator Strength For Ce 4f Electrons In The Solid State, Kwang Joo Kim, Bruce N. Harmon, David W. Lynch, Dale D. Koelling Oct 1991

Large Low-Energy Oscillator Strength For Ce 4f Electrons In The Solid State, Kwang Joo Kim, Bruce N. Harmon, David W. Lynch, Dale D. Koelling

Physics and Astronomy Publications

The conductivity sum rule applied to LaSn3, CeSn3, LaB6, and CeB6 between 1.5 and 4.35 eV shows that there is approximately one more electron contributing to the optical conductivity of the Ce compounds than to that of the analogous La compounds. From the data and band calculations we conclude that about 0.5 Ce 4f electron per atom contributes as initial states for CeSn3 in the above energy range, and about half that number of 4f electrons serve as initial states in LaSn3. This shift of oscillator strength from higher energies for atoms to lower energies ...


‘‘Γ-Α’’ Phase Transition Of Monolayer Ce On W(110), C. Gu, X. Wu, C. G. Olson, David W. Lynch Sep 1991

‘‘Γ-Α’’ Phase Transition Of Monolayer Ce On W(110), C. Gu, X. Wu, C. G. Olson, David W. Lynch

Physics and Astronomy Publications

As Ce is adsorbed on a W(110) substrate at 300 K an epitaxial layer develops at a coverage of 0.5 monolayer. LEED patterns indicate a hexagonal pattern consistent with Ce(111). As Ce is added, the lattice parameter shrinks continuously from 9% larger than that for γ-Ce to 3% smaller than that for α-Ce. 4f photoelectron spectra reveal two peaks similar to those of γ-Ce, changing relative intensity with increasing coverage to resemble those of α-Ce.