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Sum Frequency Generation Vibrational Spectroscopy of Adsorbed Amino Acids, Peptides and Proteins of Hydrophilic and Hydrophobic Solid-Water Interfaces

Description: Sum frequency generation (SFG) vibrational spectroscopy was used to investigate the interfacial properties of several amino acids, peptides, and proteins adsorbed at the hydrophilic polystyrene solid-liquid and the hydrophobic silica solid-liquid interfaces. The influence of experimental geometry on the sensitivity and resolution of the SFG vibrational spectroscopy technique was investigated both theoretically and experimentally. SFG was implemented to investigate the adsorption and organization of eight individual amino acids at model hydrophilic and hydrophobic surfaces under physiological conditions. Biointerface studies were conducted using a combination of SFG and quartz crystal microbalance (QCM) comparing the interfacial structure and concentration of two amino acids and their corresponding homopeptides at two model liquid-solid interfaces as a function of their concentration in aqueous solutions. The influence of temperature, concentration, equilibration time, and electrical bias on the extent of adsorption and interfacial structure of biomolecules were explored at the liquid-solid interface via QCM and SFG. QCM was utilized to quantify the biological activity of heparin functionalized surfaces. A novel optical parametric amplifier was developed and utilized in SFG experiments to investigate the secondary structure of an adsorbed model peptide at the solid-liquid interface.
Date: August 1, 2010
Creator: Holinga IV, G.H.
Partner: UNT Libraries Government Documents Department

Heinz Heinemann. The Berkeley Years (1978-1993)

Description: Heinz Heineman came to Berkeley in 1978 and stayed there for 15 years. This was the time of the energy crisis and we did not have anybody like him who had such a tremendous industrial experience with oil and coal conversion technology and science. He was interested in the conversion of coal to gaseous molecules and our studies with model catalysts appealed to him and attracted him. In a way, Heinz Heineman was bigger than life, since he played such a seminal role in the history of American catalysis science.
Date: August 27, 2009
Creator: Coble, Inger M.
Partner: UNT Libraries Government Documents Department


Description: Ellipsometry is concerned with the analysis and interpretation of changes in the state of polarization caused by reflection. The technique has found increasing interest in recent years for the measurement of thin films because it is unusually sensitive, disturbs the object minimally and can be applied to surfaces contained in any optically transparent medium. Film thicknesses amenable to measurement range from fractional monoatomic coverage to microscopic thicknesses. The measurement of changes in the state of polarization of light due to reflection provides an unusually sensitive tool for observing surface layers in any optically transparent environment. A fast, self-compensating ellipsometer has been used to observe the electrochemical formation of reacted surface layers. The optical effect of mass-transport boundary layers and component imperfections have been taken into account in the interpretation of results.
Date: June 1, 1977
Creator: Muller, R.H.
Partner: UNT Libraries Government Documents Department

Molecular Studies of Surfaces under Reaction Conditions; Sum Frequency Generation Vibrational Spectroscopy, Scanning Tunneling Microscopy and Ambient Pressure X-Ray Photoelectron Spectroscopy

Description: Instruments developed in our laboratory permit the atomic and molecular level study of NPs under reaction conditions (SFG, ambient pressure XPS and high pressure STM). These studies indicate continuous restructuring of the metal substrate and the adsorbate molecules, changes of oxidation states with NP size and surface composition variations of bimetallic NPs with changes of reactant molecules.
Date: November 11, 2009
Creator: Somorjai, G.A.
Partner: UNT Libraries Government Documents Department

Mask roughness induced LER: a rule of thumb -- paper

Description: Much work has already been done on how both the resist and line-edge roughness (LER) on the mask affect the final printed LER. What is poorly understood, however, is the extent to which system-level effects such as mask surface roughness, illumination conditions, and defocus couple to speckle at the image plane, and currently factor into LER limits. Here, we propose a 'rule-of-thumb' simplified solution that provides a fast and powerful method to obtain mask roughness induced LER. We present modeling data on an older generation mask with a roughness of 230 pm as well as the ultimate target roughness of 50 pm. Moreover, we consider feature sizes of 50 nm and 22 nm, and show that as a function of correlation length, the LER peaks at the condition that the correlation length is approximately equal to the resolution of the imaging optic.
Date: March 12, 2010
Creator: McClinton, Brittany & Naulleau, Patrick
Partner: UNT Libraries Government Documents Department

SQUID magnetometry from nanometer to centimeter length scales

Description: The development of Superconducting QUantum Interference Device (SQUID)-based magnetometer for two applications, in vivo prepolarized, ultra-low field MRI of humans and dispersive readout of SQUIDs for micro- and nano-scale magnetometery, are the focus of this thesis.
Date: June 28, 2010
Creator: Hatridge, Michael J.
Partner: UNT Libraries Government Documents Department

Wavelength-specific reflections: A decade of EUV actinic mask inspection research

Description: Mask inspection is essential for the success of any pattern-transfer lithography technology, and EUV Lithography in particular faces unique challenges. EUV masks resonant-reflective multilayer coatings have a narrow, wavelength-specific response that dramatically affects the way that defects appear, or disappear, at various illuminating wavelengths. Furthermore, the ever-shrinking size of 'critical' defects limits the potential effectiveness of DUV inspection techniques over time. Researchers pursuing numerous ways of finding and characterizing defects on EUV masks and have met with varying degrees of success. Their lessons inform the current, urgent exploration to select the most effective techniques for high-volume manufacturing. Ranging from basic research and demonstration experiments to commercial inspection tool prototypes, we survey the recent history of work in this area, including sixteen projects in Europe, Asia, and America. Solutions range from scanning beams to microscopy, dark field imaging to pattern transfer.
Date: December 31, 2010
Creator: Goldberg, Kenneth & Mochi, Iacopo
Partner: UNT Libraries Government Documents Department


Description: Three investigations of difference frequency generation (DFG) of far-infrared radiation by optical mixing are described: a theory of DFG by monochromatic, focused Gaussian pump laser beams, a theory of DFG by a picosecond pump laser pulse, and an experiment using ruby-pumped dye lasers. First, the theory of far-infrared generation by optical mixing of monochromatic, focused Gaussian beams in a uniaxial crystal is developed, taking into account the effects of diffraction, absorption, double refraction, and multiple reflections and total reflection at the boundary surfaces. (Reflection and transmission coefficients of a uniaxial crystal slab are derived by a new matrix technique.) Results of numerical calculations are presented. Focusing the pump beams appreciably enhances the far-infrared output despite the strong far-infrared diffraction. In a 1-cm long crystal, the optimum focal spot size is approximately equal to or smaller than the far-infrared wavelength for output frequencies less than 100 cm{sup -1}. Double refraction of the pump beams is relatively unimportant. Both far-infrared absorption and boundary reflections have major effects on the far-infrared output and its angular distribution. The former is often the factor which limits the output power. We show that a simple model treating the nonlinear polarization as a constant lie-radius Gaussian distribution of radiating dipoles adequately describes the effect of pump-beam focusing. We also compare the results of our calculations with those for second-harmonic generation. Second, a theoretical calculation of far-infrared power spectra generated by picosecond pulses in a nonlinear crystal is developed. The results are illustrated with two practical examples: LiNbO{sub 3} slabs oriented for rectification of the optical e-ray and for beating of the optical o-ray with the optical e-ray. The former is phase matched at 0 cm{sup -1}; the latter, at both the forward-(FCPM) and backward-collinear phase-matching frequencies. The one-dimensional, time-dependent electric field is discussed and then used to ...
Date: July 1, 1977
Creator: Morris, J.R.
Partner: UNT Libraries Government Documents Department

Corner rounding in EUV photoresist: tuning through molecular weight, PAG size, and development time

Description: In this paper, the corner rounding bias of a commercially available extreme ultraviolet photoresist is monitored as molecular weight, photoacid generator (PAG) size, and development time are varied. These experiments show that PAG size influences corner biasing while molecular weight and development time do not. Large PAGs are shown to exhibit less corner biasing, and in some cases, lower corner rounding, than small PAGs. In addition, heavier resist polymers are shown to exhibit less corner rounding than lighter ones.
Date: December 31, 2009
Creator: Anderson, Christopher; Daggett, Joe & Naulleau, Patrick
Partner: UNT Libraries Government Documents Department


Description: A systematic transmission electron microscopy study of carbide precipitation in quenched-aged tantalum-carbon alloys has clarified the mechanism of precipitation in refractory BCC metal-carbon alloys. Diffraction contrast analysis shows that the precipitate platelets lie on {l_brace}310{r_brace} planes of the matrix, are interstitial in nature, and fully coherent before they thicken further and lose coherency. The precipitation sequence is continuous and involves no renucleation during the formation of the non-coherent phase. Thus, the final orientation relationship of the precipitate with the matrix already is found at the earliest stage at which it is possible to detect it. The interpretation of the results indicates that, as in FCC alloys, vacancies play an important role in the precipitation process during the nucleation and early growth stages and permit the formation of the hexagonal equilibrium M{sub 2}C structure early in the sequence. The model proposed to explain the observations is also consistent with the multistage hardening observed in quenched-aged refractory metal interstitial alloys.
Date: August 1, 1980
Creator: Dahmen, U.; Westmacott, K.H. & Thomas, G.
Partner: UNT Libraries Government Documents Department

Ultraviolet Absorption Spectrum of Nitrous Oxide as Function of Temperature and Isotopic Substitution

Description: The ultraviolet absorption spectra of nitrous oxide and its {sup 15}N isotopes over the wavelength range 197 to 172 nm and between 150 and 500 K show a weak continuous absorption and a pattern of diffuse banding that became pronounced at higher temperatures. The temperature dependence of the absorption spectrum results from the activation of the n{sub 2}{double_prime} bending mode. Deconvolution of the data shows that absorption by molecules in the (010) vibrational mode results in a spectrum of vibrational bands superimposed on a continuum. A weaker and nearly continuous spectrum results from the ultraviolet absorption by molecules in the (000) vibrational mode. Analysis of the structuring indicates n{sub 2}{double_prime} = (490 {+-} 10) cm{sup -1}. No rotational structure can be observed. Measurement of the n{sub 2}{double_prime} isotope shift is used to identify the quantum number of the upper state vibrational levels. Normal coordinate analysis of the excited state is used to determine a self-consistent set of molecular parameters: bond angle (115{sup o}), the values of n{sub 1}{prime} and n{sub 3}{prime} (1372 and 1761 cm{sup -1}, respectively), and the force constants of the upper state. It is suggested that the transitions observed are {sup 1}S{sup -}({sup 1}A{sup -}) {l_arrow} X- {sup 1}{sup +} and {sup 1}D {l_arrow} {tilde X} {sup 1}S{sup +}.
Date: July 1, 1980
Creator: Selwyn, G.S. & Johnston, H.S.
Partner: UNT Libraries Government Documents Department

Hydrogenation of the alpha,beta-Unsaturated Aldehydes Acrolein, Crotonaldehyde, and Prenal over Pt Single Crystals: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

Description: Sum-frequency generation vibrational spectroscopy (SFG-VS) and kinetic measurements using gas chromatography have been used to study the surface reaction intermediates during the hydrogenation of three {alpha},{beta}-unsaturated aldehydes, acrolein, crotonaldehyde, and prenal, over Pt(111) at Torr pressures (1 Torr aldehyde, 100 Torr hydrogen) in the temperature range of 295K to 415K. SFG-VS data showed that acrolein has mixed adsorption species of {eta}{sub 2}-di-{sigma}(CC)-trans, {eta}{sub 2}-di-{sigma}(CC)-cis as well as highly coordinated {eta}{sub 3} or {eta}{sub 4} species. Crotonaldehyde adsorbed to Pt(111) as {eta}{sub 2} surface intermediates. SFG-VS during prenal hydrogenation also suggested the presence of the {eta}{sub 2} adsorption species, and became more highly coordinated as the temperature was raised to 415K, in agreement with its enhanced C=O hydrogenation. The effect of catalyst surface structure was clarified by carrying out the hydrogenation of crotonaldehyde over both Pt(111) and Pt(100) single crystals while acquiring the SFG-VS spectra in situ. Both the kinetics and SFG-VS showed little structure sensitivity. Pt(100) generated more decarbonylation 'cracking' product while Pt(111) had a higher selectivity for the formation of the desired unsaturated alcohol, crotylalcohol.
Date: November 26, 2008
Creator: Kliewer, C.J. & Somorjai, G.A.
Partner: UNT Libraries Government Documents Department

Identification of the Charge Carriers in Cerium Phosphate Ceramics

Description: The total conductivity of Sr-doped cerium orthophosphate changes by nearly two orders of magnitude depending on the oxygen and hydrogen content of the atmosphere. The defect model for the system suggests that this is because the identity of the dominant charge carrier can change from electron holes to protons when the sample is in equilibrium with air vs. humidified hydrogen. In this work are presented some preliminary measurements that can help to clarify this exchange between carriers. The conduction behavior of a 2percent Sr-doped CePO4 sample under symmetric atmospheric conditions is investigated using several techniques, including AC impedance, H/D isotope effects, and chronoamperometry.
Date: June 2, 2010
Creator: Ray, Hannah L. & Jonghe, Lutgard C. De
Partner: UNT Libraries Government Documents Department


Description: Chemical yields of Fe{sup 3+} have been measured from FeSO{sub 4} solutions irradiated in the presence and absence of oxygen with carbon, neon, and argon ions from the Berkeley Bevalac facility. G(Fe{sup 3+}) decreases with increasing beam penetration and with increasing atomic number of the incident ion. The results are compared with current theoretical expectations of the behavior of these particles in an aqueous absorber. The chemical yields are consistently higher than theoretically predicted, by amounts varying from <6.2% (carbon ions) to <13.2% (argon ions). The additional yields are possibly attributable to fragmentation of the primary particle beams.
Date: July 1, 1980
Creator: Christman, E.A.; Appleby, A. & Jayko, M.
Partner: UNT Libraries Government Documents Department

Random walk approach to spin dynamics in a two-dimensional electron gas with spin-orbit coupling

Description: We introduce and solve a semiclassical random walk (RW) model that describes the dynamics of spin polarization waves in zinc-blende semiconductor quantum wells. We derive the dispersion relations for these waves, including the Rashba, linear and cubic Dresselhaus spin-orbit interactions, as well as the effects of an electric field applied parallel to the spin polarization wave vector. In agreement with calculations based on quantum kinetic theory [P. Kleinert and V. V. Bryksin, Phys. Rev. B 76, 205326 (2007)], the RW approach predicts that spin waves acquire a phase velocity in the presence of the field that crosses zero at a nonzero wave vector, q{sub 0}. In addition, we show that the spin-wave decay rate is independent of field at q{sub 0} but increases as (q-q{sub 0}){sup 2} for q {ne} q{sub 0}. These predictions can be tested experimentally by suitable transient spin grating experiments.
Date: September 27, 2010
Creator: Yang, Luyi; Orenstein, J. & Lee, Dung-Hai
Partner: UNT Libraries Government Documents Department

Iterative procedure for in-situ EUV optical testing with an incoherent source

Description: We propose an iterative method for in-situ optical testing under partially coherent illumination that relies on the rapid computation of aerial images. In this method a known pattern is imaged with the test optic at several planes through focus. A model is created that iterates through possible aberration maps until the through-focus series of aerial images matches the experimental result. The computation time of calculating the through-focus series is significantly reduced by a-SOCS, an adapted form of the Sum Of Coherent Systems (SOCS) decomposition. In this method, the Hopkins formulation is described by an operator S which maps the space of pupil aberrations to the space of aerial images. This operator is well approximated by a truncated sum of its spectral components.
Date: December 1, 2009
Creator: Miyawaka, Ryan; Naulleau, Patrick & Zakhor, Avideh
Partner: UNT Libraries Government Documents Department

Dual Selectivity Expressed in [2+2+1] Dynamic Clipping of Unsymmetrical [2]Catenanes

Description: A {pi}-templated dynamic [2+2+1] clipping protocol is established for the synthesis of [2]catenanes from two parts dialdehyde, two parts diamine and one part tetracationic cyclophane. It is further diversified for the selective formation of an unsymmetrical [2]catenane showing great translational selectivity by employing two different dialdehydes in a one-pot reaction. The dual selectivity and the dynamic nature are verified by {sup 1}H NMR spectroscopy, X-ray single crystal structural studies and exchange experiments.
Date: June 11, 2010
Creator: Liu, Yi
Partner: UNT Libraries Government Documents Department


Description: We report the development of the composite superconducting transition edge bolometer. The temperature sensitive element is an aluminum strip evaporated onto the sapphire substrate. A bismuth film evaporated on the reverse side of the substrate is used to absorb the submillimeter radiation. The noise limitation of the bolometer is calculated. The fabrication and measured performance are described. The best electrical NEP (noise-equivalent-power) obtained is (1.7 {+-} 0.1) x 10{sup -15} WHz{sup -1/2} at 2 Hz at an operating temperature of 1.27 K. This NEP is within a factor of 2 of the thermal noise limit. The effective absorptivity of the bismuth film is measured to be 0.47 {+-} 0.05, and the corresponding detectivity D* is calculated to be (1.1 {+-} 0.1) x 10{sup 14} cm w{sup -1}Hz{sup 1/2}. Suggestions are made for further improvements in sensitivity. The current-dependent noise in thin metal films at the superconducting transition has been further investigated. The measured noise power spectrum of the tin film on sapphire substrate at the superconducting transition is compared with the cosine transforms of the decay curves obtained from step-function and {delta}-function thermal perturbations. The nature of the noise driving term is found to be a random current flowing inside the sample, in agreement with the uncorrelated thermal fluctuation model. This result is consistent with the case of a freely suspended tin fiber at the superconducting transition, but in contrast to the room temperature measurement where the cosine transform of the step-function response gives the noise power spectrum, in agreement with the correlated fluctuation model.
Date: June 1, 1978
Creator: Yeh, Nan-Hsiung
Partner: UNT Libraries Government Documents Department

Actinic imaging of native and programmed defects on a full-field mask

Description: We describe the imaging and characterization of native defects on a full field extreme ultraviolet (EUV) mask, using several reticle and wafer inspection modes. Mask defect images recorded with the SEMA TECH Berkeley Actinic Inspection Tool (AIT), an EUV-wavelength (13.4 nm) actinic microscope, are compared with mask and printed-wafer images collected with scanning electron microscopy (SEM) and deep ultraviolet (DUV) inspection tools. We observed that defects that appear to be opaque in the SEM can be highly transparent to EUV light, and inversely, defects that are mostly transparent to the SEM can be highly opaque to EUV. The nature and composition of these defects, whether they appear on the top surface, within the multilayer coating, or on the substrate as buried bumps or pits, influences both their significance when printed, and their detectability with the available techniques. Actinic inspection quantitatively predicts the characteristics of printed defect images in ways that may not be possible with non-EUV techniques. As a quantitative example, we investigate the main structural characteristics of a buried pit defect based on EUV through-focus imaging.
Date: March 12, 2010
Creator: Mochi, I.; Goldberg, K. A.; Fontaine, B. La; Tchikoulaeva, A. & Holfeld, C.
Partner: UNT Libraries Government Documents Department

Photon flux requirements for EUV reticle imaging microscopy in the 22 and 16 nm nodes

Description: EUV-wavelength actinic microscopy yields detailed information about EUV mask patterns, architectures, defects, and the performance of defect repair strategies, without the complications of photoresist imaging. The measured aerial image intensity profiles provide valuable feedback to improve mask and lithography system modeling methods. In order to understand the photon-flux-dependent pattern measurement limits of EUV mask-imaging microscopy, we have investigated the effects of shot noise on aerial image linewidth measurements for lines in the 22 and 16-nm generations. Using a simple model of image formation near the resolution limit, we probe the influence of photon shot noise on the measured, apparent line roughness. With this methodology, we arrive at general flux density requirements independent of the specific EUV microscope configurations. Analytical and statistical analysis of aerial image simulations in the 22 and 16-nm generations reveal the trade-offs between photon energy density (controllable with exposure time), effective pixel dimension on the CCO (controlled by the microscope's magnification ratio), and image log slope (ILS). We find that shot-noise-induced linewidth roughness (LWR) varies imersely with the square root of the photon energy density, and is proportional to the imaging magnification ratio. While high magnification is necessary for adequate spatial resolution, for a given flux density, higher magnification ratios have diminishing benefits. With practical imaging parameters, we find that in order to achieve an LWR (3{sigma}) value of 5% of linewidth for dense, 88-nm mask features with 80% aerial image contrast and 13.5-nm effective pixel width (1000x magnification ratio), a peak photon flux of approximately 1400 photons per pixel per exposure is required.
Date: March 12, 2010
Creator: Wintz, D.; Goldberg, K. A.; Mochi, I. & Huh, S.
Partner: UNT Libraries Government Documents Department

Direct Photonic-Plasmonic Coupling and Routing in Single Nanowires

Description: Metallic nanoscale structures are capable of supporting surface plasmon polaritons (SPPs), propagating collective electron oscillations with tight spatial confinement at the metal surface. SPPs represent one of the most promising structures to beat the diffraction limit imposed by conventional dielectric optics. Ag nano wires have drawn increasing research attention due to 2D sub-100 nm mode confinement and lower losses as compared with fabricated metal structures. However, rational and versatile integration of Ag nanowires with other active and passive optical components, as well as Ag nanowire based optical routing networks, has yet to be achieved. Here, we demonstrate that SPPs can be excited simply by contacting a silver nanowire with a SnO2 nanoribbon that serves both as an unpolarized light source and a dielectric waveguide. The efficient coupling makes it possible to measure the propagation-distance-dependent waveguide spectra and frequency-dependent propagation length on a single Ag nanowire. Furthermore, we have demonstrated prototypical photonic-plasmonic routing devices, which are essential for incorporating low-loss Ag nanowire waveguides as practical components into high-capacity photonic circuits.
Date: October 20, 2009
Creator: Yan, Rouxue; Pausauskie, Peter; Huang, Jiaxing & Yang, Piedong
Partner: UNT Libraries Government Documents Department

Propagation of guided modes in curved nanoribbon waveguides

Description: The authors develop a plane-wave-based transfer matrix method in curvilinear coordinates to study the guided modes in curved nanoribbon waveguides. The problem of a curved structure is transformed into an equivalent one of a straight structure with spatially dependent tensors of dielectric constant and magnetic permeability. The authors investigate the coupling between the eigenmodes of the straight part and those of the curved part when the waveguide is bent. The authors show that curved sections can result in strong oscillations in the transmission spectrum similar to the recent experimental results of Lawet al.
Date: August 23, 2006
Creator: Yang, P.; Ye, Zhuo; Hu, Xinhua; Li, Ming & Ho, Kai-Ming
Partner: UNT Libraries Government Documents Department


Description: We report the development of an instrument for gas-phase ultraviolet photoelectron spectroscopy which opens several new areas for study through use of the supersonic molecular beam technique. The key features in which we have sought an improvement on earlier spectrometer designs are (1) the optimization of electron energy resolution and sensitivity, (2) vacuum isolation, and (3) the capability for mass spectrometric analysis. Our principal interests are in the high resolution spectroscopy of small molecules and in studies of weakly bound complexes formed under collisionless conditions. As shown in Fig. 1 the apparatus is essentially a molecular beam chamber with allowance for access by a beam source, an electron energy analyzer, and a quadrupole mass spectrometer. These three plug-in units are equipped with individual differential pumping systems. The photon source is a rare-gas resonance lamp which may be directed toward the molecular beam either 90{sup o} or 54.7{sup o} from the direction of electron collection. Electrons which pass through entrance aperture are transported by a series of electrostatic lenses to a 90{sup o} spherical sector pre-analyzer (R{sub 0} = 3.8 cm) and then on to a 180{sup o} hemispherical analyzer (R{sub 0} = 10.2 cm). The detector consists of a microchannel plate electron multiplier (40 mm diam.) with a resistive-anode position encoder. The function of the pre-analyzer is to improve the signal-to-noise ratio by reducing the background of scattered electrons incident upon the microchannel plate. The electron optical system is designed such that the energy bandpass (FWHN) leaving the pre-analyzer just fills the energy window presented by the multichannel detector. The multichannel capability of this analyzer is very advantageous for working with the rather low number density (< 10{sup 13} cm{sup -3}) of molecular beam samples, since the data collection rate is improved by more than an order of magnitude over ...
Date: June 1, 1981
Creator: Pollard, J.E.; Trevor, D.J.; Lee, Y.T. & Shirley, D.A.
Partner: UNT Libraries Government Documents Department