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Non-free-electron momentum- and thickness-dependent evolution ofquantum well states in the Cu/Co/Cu(001) system

Description: We present systematic k{sub {parallel}}-dependent measurements of the Fermi surface and underlying band structure of quantum well states in Cu/Co/Cu(001). Compared to bands from normal emission, we find a complicated evolution of ''split'' QW states as a function of the thicknesses of both the copper overlayer and the cobalt barrier layer. Self-consistent calculations show that the penetration of the quantum well states into the cobalt barrier layer is significant and leads to the observed very non-free-electron behavior of these states.
Date: May 21, 2005
Creator: Rotenberg, Eli; Wu, Y.Z.; An, Joonhee M.; Van Hove, Michel A.; Canning, Andrew; Wang, Lin-Wang et al.
Partner: UNT Libraries Government Documents Department

Electron-Phonon Coupling in High-Temperature CuprateSuperconductors as Revealed by Angle-resolved PhotoemissonSpectroscopy

Description: We present an application programming interface (API) used to simplify application-level access to both data and semantic range query machinery where both data and search indices are stored and accessed using the HDF5 data model. While the APIs for HDF5 data access and FastBit indexing/query are rather complex, our API simplifies use of these powerful software technologies.
Date: May 1, 2005
Creator: Zhou, X.J.; Hussain, Z. & Shen, Z.-X.
Partner: UNT Libraries Government Documents Department

Determination of Band Curvatures by Angle-resolved Two-photonPhotoemission in thin films of C(60) on Ag(111)

Description: The thickness-dependent interfacial band structure wasdetermined for thin films of Co(6) on Ag(111) by angle-resolvedtwo-photon photoemission spectroscopy.
Date: March 1, 2005
Creator: Shipman, Steven T.; Szymanski, Paul; Garrett-Roe, Sean; Yang,Aram; Strader, Matthew L. & Harris, Charles B.
Partner: UNT Libraries Government Documents Department


Description: Preventing the corrosion and oxidation of uranium is important to the continued development of advanced nuclear fuel technologies. Knowledge of the surface reactions of uranium metal with various environmental and atmospheric agents, and the subsequent degradation processes, are vitally important in 21st century nuclear technology. A review of the oxidation of actinide elements and their use in catalysis summarizes the present understanding of the kinetics and mechanisms of the reaction in dry and humid air. Researchers have recently used N{sub 2}{sup +} and C{sup +} ion implantation to modify the near surface region chemistry and structure of U to affect the nucleation and growth kinetics of corrosion and to passivate the surface. These researchers used Auger electron spectroscopy (AES) in conjunction with sputter depth profiling to show that the implanted surfaces had compositional gradients containing nitrides and carbides. In addition to chemical modification, ion implantation can create special reactive surface species that include defect structures that affect the initial absorption and dissociation of molecules on the surface, thus providing mechanical stability and protection against further air corrosion.
Date: April 21, 2005
Creator: Nelson, A J; Felter, T E; Wu, K J; Evans, C; Ferreira, J L; Siekhaus, W J et al.
Partner: UNT Libraries Government Documents Department

Evidence for the Spectroscopic Signature of Aging in (delta)-Pu(Ga)

Description: Plutonium, because of its radioactive nature, ages from the 'inside out' by means of self-irradiation damage and thus produces nanoscale internal defects. The self-irradiation induced defects come in the form of Frenkel-type defects (vacancies and self-interstitial atoms), helium in-growth, and defect clusters. At present there are neither experimental nor theoretical models describing the changes in the electronic structure caused by the aging in Pu. This fact appears to be associated primarily with the absence of reasonably convincing spectroscopic evidence of the changes. This paper demonstrates that Resonant Photoemission, a variant of Photoelectron Spectroscopy, has strong sensitivity to aging of Pu samples. The spectroscopic results are correlated with an extra-atomic screening model [1], and are shown to be the fingerprint of mesoscopic or nanoscale internal damage in the Pu physical structure. This means that a spectroscopic signature of internal damage due to aging in Pu has been established.
Date: November 23, 2005
Creator: Chung, B W; Schwartz, A J; Ebbinghaus, B B; Fluss, M J; Haslam, J J; Blobaum, K M et al.
Partner: UNT Libraries Government Documents Department

Spin-Resolved Electronic Structure Studies of Non-Magnetic Systems: Possible Observation of the Fano Effect in Polycrystal Ce

Description: The valence electronic structure and electron spectra of Cerium remain a subject of uncertainty and controversy. Perhaps the best and most direct method of ascertaining the valence electronic structure is the application of electron spectroscopies [1-17], e.g. photoelectron spectroscopy for the occupied states [1-10, 12-14] and x-ray absorption [2] and Bremstrahlung Isochromat Spectroscopy (inverse photoelectron spectroscopy) [3,11,13] for the unoccupied states. Much of the controversy revolves around the interpretation of the Ce photoemission structure in terms of a modified Anderson Impurity Model [15,16]. Here, in this correlated and multi-electronic picture, semi-isolated 4f states (at a nominal binding energy of 1 eV) are in contact with the bath of spd valence electrons, generating spectral features at the Fermi Level and at a binding energy corresponding to the depth of the bath electron well, about 2 eV below the Fermi Level in the case of Ce. This controversy has spilled over into issues such as the volume collapse associated with the alpha to gamma phase transition [17-19] and the electronic structure of Ce compounds [20-23]. (A more generalized schematic illustrating the competition between the bandwidth (W) and correlation strength (U) is shown in Figure 1.) Considering the remaining uncertainty associated with the spectral features and valence electronic structure of Ce, it seemed plausible that the situation would benefit from the application of a spectroscopy with increased resolution and probing power. To this end, we have applied circularly polarized soft x-rays and true spin detection, in a modified form of the photoelectron spectroscopy experiment, to the enigmatic Ce system. The result of this is that we have observed the first evidence of the Fano Effect in the valence electronic features of non-magnetic Cerium ultra-thin films.
Date: June 1, 2005
Creator: Tobin, J; Morton, S; Chung, B; Yu, S & Waddill, G
Partner: UNT Libraries Government Documents Department

Chemical states and electronic structure of a HfO(-2) / Ge(001) interface

Description: We report the chemical bonding structure and valence band alignment at the HfO{sub 2}/Ge (001) interface by systematically probing various core level spectra as well as valence band spectra using soft x-rays at the Stanford Synchrotron Radiation Laboratory. We investigated the chemical bonding changes as a function of depth through the dielectric stack by taking a series of synchrotron photoemission spectra as we etched through the HfO{sub 2} film using a dilute HF-solution. We found that a very non-stoichiometric GeO{sub x} layer exists at the HfO{sub 2}/Ge interface. The valence band spectra near the Fermi level in each different film structure were carefully analyzed, and as a result, the valence band offset between Ge and GeO{sub x} was determined to be {Delta}E{sub v} (Ge-GeO{sub x}) = 2.2 {+-} 0.15 eV, and that between Ge and HfO{sub 2}, {Delta}E{sub v} (Ge-HfO{sub 2}) = 2.7 {+-} 0.15 eV.
Date: May 4, 2005
Creator: Seo, Kang-ill; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.; Sun, Shiyu; Lee, Dong-Ick; Pianetta, Piero et al.
Partner: UNT Libraries Government Documents Department

Angle Resolved Photoemission Spectroscopy Studies of the Mott Insulator to Superconductor Evolution in Ca2-xNaxCuO2Cl2

Description: It is widely believed that many of the exotic physical properties of the high-T{sub c} cuprate superconductors arise from the proximity of these materials to the strongly correlated, antiferromagnetic Mott insulating state. Therefore, one of the fundamental questions in the field of high-temperature superconductivity is to understand the insulator-to-superconductor transition and precisely how the electronic structure of Mott insulator evolves as the first holes are doped into the system. This dissertation presents high-resolution, doping dependent angle-resolved photoemission (ARPES) studies of the cuprate superconductor Ca{sub 2-x}Na{sub x}CuO{sub 2}Cl{sub 2}, spanning from the undoped parent Mott insulator to a high-temperature superconductor with a T{sub c} of 22 K. A phenomenological model is proposed to explain how the spectral lineshape, the quasiparticle band dispersion, and the chemical potential all progress with doping in a logical and self-consistent framework. This model is based on Franck-Condon broadening observed in polaronic systems where strong electron-boson interactions cause the quasiparticle residue, Z, to be vanishingly small. Comparisons of the low-lying states to different electronic states in the valence band strongly suggest that the coupling of the photohole to the lattice (i.e. lattice polaron formation) is the dominant broadening mechanism for the lower Hubbard band states. Combining this polaronic framework with high-resolution ARPES measurements finally provides a resolution to the long-standing controversy over the behavior of the chemical potential in the high-T{sub c} cuprates. This scenario arises from replacing the conventional Fermi liquid quasiparticle interpretation of the features in the Mott insulator by a Franck-Condon model, allowing the reassignment of the position of the quasiparticle pole. As a function of hole doping, the chemical potential shifts smoothly into the valence band while spectral weight is transferred from incoherent weight at high energies to a coherent quasiparticle peak near E{sub F}. The combined shift in the chemical potential and ...
Date: September 2, 2005
Creator: Shen, Kyle Michael
Partner: UNT Libraries Government Documents Department

Study of f electron correlations in nonmagnetic Ce by means of spin resolved resonant photoemission

Description: We have studied the spin-spin coupling between two f electrons of nonmagnetic Ce by means of spin resolved resonant photoemission using circularly polarized synchrotron radiation. The two f electrons participating in the 3d{sub 5/2} {yields} 4f resonance process are coupled in a singlet while the coupling is veiled in the 3d{sub 3/2} {yields} 4f process due to an additional Coster-Kronig decay channel. The identical singlet coupling is observed in the 4d {yields} 4f resonance process. Based on the Ce measurements, it is argued that spin resolved resonant photoemission is a unique approach to study the correlation effects, particularly in the form of spin, in the rare-earths and the actinides.
Date: November 28, 2005
Creator: Yu, S; Komesu, T; Chung, B W; Waddill, G D; Morton, S A & Tobin, J G
Partner: UNT Libraries Government Documents Department

Spectroscopic Signature of Aging in (delta)-Pu(Ga)

Description: Resonant Photoemission, a variant of Photoelectron Spectroscopy, has been demonstrated to have sensitivity to aging of Pu samples. The spectroscopic results are correlated with resistivity measurements and are shown to be the fingerprint of mesoscopic or nanoscale internal damage in the Pu physical structure. This means that a spectroscopic signature of internal damage due to aging in Pu has been established.
Date: April 15, 2005
Creator: Chung, B W; Schwartz, A J; Ebbinghaus, B B; Fluss, M J; Haslam, J J; Blobaum, K M et al.
Partner: UNT Libraries Government Documents Department

Nitrogen Doping and Thermal Stability in HfSiOxNy Studied by Photoemission and X-ray Absorption Spectroscopy

Description: We have investigated nitrogen-doping effects into HfSiO{sub x} films on Si and their thermal stability using synchrotron-radiation photoemission and x-ray absorption spectroscopy. N 1s core-level photoemission and N K-edge absorption spectra have revealed that chemical-bonding states of N-Si{sub 3-x}O{sub x} and interstitial N{sub 2}-gas-like features are clearly observed in as-grown HfSiO{sub x}N{sub y} film and they decrease upon ultrahigh vacuum (UHV) annealing due to a thermal instability, which can be related to the device performance. Annealing-temperature dependence in Hf 4f and Si 2p photoemission spectra suggests that the Hf-silicidation temperature is effectively increased by nitrogen doping into the HfSiO{sub x} although the interfacial SiO{sub 2} layer is selectively reduced. No change in valence-band spectra upon UHV annealing suggests that crystallization of the HfSiO{sub x}N{sub y} films is also hindered by nitrogen doping into the HfSiO{sub x}.
Date: December 14, 2005
Creator: Toyoda, Satoshi; Okabayashi, Jun; Takahashi, Haruhiko; Oshima, Masaharu; U., /Tokyo; Lee, Dong-Ick et al.
Partner: UNT Libraries Government Documents Department

Surface Passivation of Germanium Nanowires

Description: The surface of single crystal, cold-wall CVD-grown germanium nanowires was studied by synchrotron radiation photoemission spectroscopy (SR-PES) and also by conventional XPS. The as-grown germanium nanowires seem to be hydrogen terminated. Exposure to laboratory atmosphere leads to germanium oxide growth with oxidation states of Ge{sup 1+}, Ge{sup 2+}, Ge{sup 3+}, while exposure to UV light leads to a predominance of the Ge{sup 4+} oxidation state. Most of the surface oxide could be removed readily by aqueous HF treatment which putatively leaves the nanowire surface hydrogen terminated with limited stability in air. Alternatively, chlorine termination could be achieved by aq. HCl treatment of the native oxide-coated nanowires. Chlorine termination was found to be relatively more stable than the HF-last hydrogen termination.
Date: May 13, 2005
Creator: Adhikari, Hemant; Sun, Shiyu; Pianetta, Piero; Chidsey, Chirstopher E.D.; McIntyre, Paul C. & /SLAC, SSRL
Partner: UNT Libraries Government Documents Department

Quantum Efficiency and Topography of Heated and Plasma-Cleaned Copper Photocathode Surfaces

Description: We present measurements of photoemission quantum efficiency (QE) for copper photocathodes heated and cleaned by low energy argon and hydrogen ion plasma. The QE and surface roughness parameters were measured before and after processing and surface chemical composition was tracked in-situ with x-ray photoelectron spectroscopy (XPS). Thermal annealing at 230 C was sufficient to improve the QE by 3-4 orders of magnitude, depending on the initial QE. Exposure to residual gas slowly reduced the QE but it was easily restored by argon ion cleaning for a few minutes. XPS showed that the annealing or ion bombardment removed surface water and hydrocarbons.
Date: August 4, 2005
Creator: Palmer, Dennis T.; PSD, /Titan; Kirby, R.E.; King, F.K. & /SLAC
Partner: UNT Libraries Government Documents Department

Quarterly progress report for Q1 FY06 for Complex Transient Events in Materials Studied Using Ultrafast Electron Probes and Terascale Simulation (FWP SCW0289)

Description: This quarter (Q1 FY06) marked the first time that the LLNL dynamic transmission electron microscope (DTEM) configuration had advanced to the point whereby it was possible to conduct in-situ experiments on specimens. DTEM improvements continue to progress at a rapid pace. We summarize important achievements in the following list: (1) Instrument performance and design improvements - (a) Reproducibly achieving >1 x 10{sup 7} e{sup -} per pulse. Adjustments in the cathode laser system design led to an improved quantum efficiency and electron yield per pulse. The current number of electrons in the pulse is sufficient for acquiring high quality, single-shot electron diffraction patterns. (b) Implementation of computer interface and Labview{reg_sign} programs for cathode and specimen drive alignment and cathode and pump laser trigger and delay settings. These controls provide a user friendly interface and ease in the experimental setup and implementation. (c) Cathode test chamber (offline test apparatus to asses photocathode design and laser induced photoemission) construction has been completed. (2) Notable instrument features brought into service - (a) Drive laser system was enhanced to improve beam shape and uniformity and to include continuous laser energy monitoring. The drive laser spot size on the specimen was also reduced from 70 {mu}m x 110 {mu}m to 50 {mu}m x 75 {mu}m. (b) New phosphor coated face plate manufactured by TVIPS was installed. The sensitivity and signal noise ratio improved by factor 2 (sensitivity {approx}110 CCD counts/e{sup -} and signal to noise ratio {approx}5). (3) Experimental Progress - (a) First time-resolved experiment: observation of the {alpha} (hcp) to {beta} (bcc) phase transition in pure Ti films via single shot electron diffraction. Results of this experiment were published in the MRS Fall 2005 proceedings and are under review for article in the FEMMS proceedings, which will to be published in Journal of Material ...
Date: December 27, 2005
Creator: Campbell, G.
Partner: UNT Libraries Government Documents Department

Uranium passivation by C+ implantation: a photoemission and secondary ion mass spectrometry study

Description: Implantation of 33 keV C{sup +} ions into polycrystalline U{sup 238} with a dose of 4.3 x 10{sup 17} cm{sup -2} produces a physically and chemically modified surface layer that prevents further air oxidation and corrosion. X-ray photoelectron spectroscopy and secondary ion mass spectrometry were used to investigate the surface chemistry and electronic structure of this C{sup +} ion implanted polycrystalline uranium and a non-implanted region of the sample, both regions exposed to air for more than a year. In addition, scanning electron microscopy was used to examine and compare the surface morphology of the two regions. The U 4f, O 1s and C 1s core-level and valence band spectra clearly indicate carbide formation in the modified surface layer. The time-of-flight secondary ion mass spectrometry depth profiling results reveal an oxy-carbide surface layer over an approximately 200 nm thick UC layer with little or no residual oxidation at the carbide layer/U metal transitional interface.
Date: January 20, 2005
Creator: Nelson, A J; Felter, T E; Wu, K J; Evans, C; Ferreira, J; Siekhaus, W et al.
Partner: UNT Libraries Government Documents Department

4th-International Symposium on Ultrafast Surface Science - Final Report

Description: The 4-th International Symposium on Ultrafast Surface Dynamics (UDS4) was held at the Telluride Summer Research Center on June 22-27, 2003. The International Organizing Committee consisting of Hrvoje Petek (USA), Xiaoyang Zhu (USA), Pedro Echenique (Spain) and Maki Kawai (Japan) brought together a total of 51 participants 16 of whom were from Europe, 10 from Japan, and 25 from the USA. The focus of the conference was on ultrafast electron or light induced processes at well-defined surfaces. Ultrafast surface dynamics concerns the transfer of charge and energy at solid surfaces on the femtosecond time scale. These processes govern rates of fundamental steps in surface reactions, interfacial electron transfer in molecular electronics, and relaxation in spin transport. Recent developments in femtosecond laser technology make it possible to measure by a variety of nonlinear optical techniques directly in the time domain the microscopic rates underlying these interfacial processes. Parallel progress in scanning probe microscopy makes it possible at a single molecular level to perform the vibrational and electronic spectroscopy measurements, to induce reactions with tunneling electrons, and to observe their outcome. There is no doubt that successful development in the field of ultrafast surface dynamics will contribute to many important disciplines.
Date: January 26, 2005
Creator: Petek, Hrvoje
Partner: UNT Libraries Government Documents Department

A photoemission study of Pd ultrathin films on Pt(111)

Description: The origin of surface core-level shift (SCLS) of Pd thin films on Pt(111) substrate is investigated. At sub-monolayer coverage of Pd thin films, the splitting of Pd 3d core level peaks indicate the contribution of both initial and final-state of photo-ionization processes while there is almost no change on valence band (VB) spectra. When the coverage of Pd reaches to single monolayer, the final-state relaxation effect on the Pd 3d vanishes and only the initial-state effect, a negative SCLS, is present. Also, the VB spectrum at Pd monolayer films shows a clear band narrowing, that is the origin of the negative SCLS at monolayer coverage. As the Pd coverage is increased to more than monolayer thickness, the Pd 3d peaks start to show the surface layer contribution from second and third layers, positive SCLS, and the VB spectrum shows even narrower band width, possibly due to the formation of surface states and strained effect of Pd adlayers on top of the first pseudomorphic layer.
Date: May 11, 2005
Creator: Mun, Bongjin Simon; Lee, Choongman; Stamenkovic, Vojislav; Markovic, Nenad M. & Ross Jr., Philip N.
Partner: UNT Libraries Government Documents Department

Advanced 3D Photocathode Modeling and Simulations Final Report

Description: High brightness electron beams required by the proposed Next Linear Collider demand strong advances in photocathode electron gun performance. Significant improvement in the production of such beams with rf photocathode electron guns is hampered by the lack high-fidelity simulations. The critical missing piece in existing gun codes is a physics-based, detailed treatment of the very complex and highly nonlinear photoemission process.
Date: June 6, 2005
Creator: Dimitrov, Dimitre A. & Bruhwiler, David L.
Partner: UNT Libraries Government Documents Department

Evidence against a charge density wave on Bi(111)

Description: The Bi(111) surface was studied by scanning tunneling microscopy (STM), transmission electron microscopy (TEM) and angle-resolved photoemission (ARPES) in order to verify the existence of a recently proposed surface charge density wave (CDW) [Ch. R. Ast and H. Hoechst Phys. Rev. Lett. 90, 016403 (2003)]. The STM and TEM results to not support a CDW scenario at low temperatures. Furthermore, the quasiparticle interference pattern observed in STM confirms the spin-orbit split character of the surface states which prevents the formation of a CDW, even in the case of good nesting. The dispersion of the electronic states observed with ARPES agrees well with earlier findings. In particular, the Fermi contour of the electron pocket at the centre of the surface Brillouin zone is found to have a hexagonal shape. However, no gap opening or other signatures of a CDW phase transition can be found in the temperature-dependent data.
Date: May 1, 2005
Creator: Kim, T.K.; Wells, J.; Kirkegaard, C.; Li, Z.; Hoffmann, S.V.; Gayone, J.E. et al.
Partner: UNT Libraries Government Documents Department

Evidence of vectorial photoelectric effect on copper

Description: Quantum Efficiency (QE) measurements of single photon photoemission from a Cu(111) single crystal and a Cu polycrystal photocathodes, irradiated by 150 fs-6.28 eV laser pulses, are reported over a broad range of incidence angle, both in s and p polarizations. The maximum QE (approx. = 4x10-4) for polycrystalline Cu is obtained in p polarization at an angle of incidence theta = 65 deg. We observe a QE enhancement in p polarization which can not be explained in terms of optical absorption, a phenomenon known as vectorial photoelectric effect. Issues concerning surface roughness and symmetry considerations are addressed. An explanation in terms of non local conductivity tensor is proposed.
Date: May 27, 2005
Creator: Pedersoli, E.; Banfi, F.; Ressel, B.; Pagliara, S.; Giannetti,C.; Galimberti, G. et al.
Partner: UNT Libraries Government Documents Department

Advanced Strained-Superlattice Photocathodes for Polarized Electron Sources

Description: Polarized electrons have been essential for high-energy parity-violating experiments and measurements of the nucleon spin structure. The availability of a polarized electron beam was crucial to the success of the Stanford Linear Collider (SLC) in achieving a precise measurement of the electroweak mixing angle, and polarized electron beams will be required for all future linear colliders. Polarized electrons are readily produced by GaAs photocathode sources. When a circularly polarized laser beam tuned to the bandgap minimum is directed to the negative-electron-affinity (NEA) surface of a GaAs crystal, longitudinally polarized electrons are emitted into vacuum. The electron polarization is easily reversed by reversing the laser polarization. The important properties of these photocathodes for accelerator applications are: degree of polarization of the extracted beam; ability to extract sufficient charge to meet accelerator pulse-structure requirements; efficiency and stability of operation; and absence of any asymmetries in the beam properties (charge, position, energy, etc.) upon polarization reversal. The performance of GaAs photocathodes has improved significantly since they were first introduced in 1978 [1]. The theoretical maximum polarization of 50% for natural GaAs was first exceeded in 1991 using the lattice mismatch of a thin InGaAs layer epitaxially grown over a GaAs substrate to generate a strain in the former that broke the natural degeneracy between the heavy- and light-hole valence bands [2]. Polarizations as high as 78% were produced for the SLC from photocathodes based on a thin GaAs epilayer grown on GaAsP [3,4]. After 10 years of experience with many cathode samples at several laboratories [5], the maximum polarization using the GaAs/GaAsP single strained-layer cathode remained limited to 80%, while the quantum efficiency (QE) for a 100-nm epilayer is only 0.3% or less. Two factors were known to limit the polarization of these cathodes: (1) the limited band splitting; and (2) a relaxation ...
Date: January 31, 2005
Creator: Moy, Dr. Aaron
Partner: UNT Libraries Government Documents Department


Description: We have developed a new multichannel detector for use in photoelectron spectroscopy (as well as other types of high-count-rate spectroscopy) that will operate at rates of up to 1 GHz. Such detectors are crucial to the full utilization of the high-brightness radiation generated by third-generation synchrotron radiation sources. In addition, new software and hardware has been developed to permit rapidly and accurately scanning photoelectron spectra that will be accumulated in as little as a 200 micros. A versatile next-generation sample goniometer permitting equally rapid scanning of specimen angles or photon energies for angle-resolved photoemission studies, photoelectron diffraction, and photoelectron holography measurements, and cooling to below 10K has also been designed and constructed. These capabilities have been incorporated into a unique photoelectron spectrometer/diffractometer at the Advanced Light Source of the Lawrence Berkeley National Laboratory; this experimental system includes ultrahigh energy resolution, in situ rotation, variable polarization, and optional spin detection. This overall system is now being used in studies of a variety of problems including magnetic metals and oxides; metal/metal, metal/metal oxide, and metal-oxide/metal-oxide multilayers; and systems exhibiting giant and colossal magnetoresistance.
Date: October 16, 2005
Creator: Charles S. Fadley, Principal Investigator
Partner: UNT Libraries Government Documents Department