Change In Linewidth Research Articles

TiO2- and CeO2-Based Biphasic Core–Shell Nanoparticles with Tunable Core Sizes and Shell Thicknesses

A layer-by-layer methodology was used for synthesizing CeO2/TiO2 and TiO2/CeO2 core–shell nanoparticles supported in Vycor glass pores. The layers were deposited by cerium- or titanium-based metalloorganic precursor decomposition. Sequential depositions promoted linear mass increases of the Vycor pieces and a linear decrease of both total pore size and total surface area, confirmed by N2 adsorption–desorption isotherms. Alternation in the metalloorganic precursors used results in the formation of spherelike nanoparticles (as observed by HRTEM) with core–shell architecture. Raman spectroscopy data showed that CeO2 is crystallized in the fluorite structure and TiO2 in the anatase phase. Shifts in the frequency and changes in line width of TiO2 Eg and CeO2 T2g Raman bands were used for monitoring changes in core size and shell thickness based on the quantum size effect and on the phonon confinement theory. Our results show that nanoparticle core sizes and the shell thicknesses can be tuned by changing the nu...

Temperature dependent equilibrium native to unfolded protein dynamics and properties observed with IR absorption and 2D IR vibrational echo experiments.

Dynamic and structural properties of carbonmonoxy (CO)-coordinated cytochrome c(552) from Hydrogenobacter thermophilus (Ht-M61A) at different temperatures under thermal equilibrium conditions were studied with infrared absorption spectroscopy and ultrafast two-dimensional infrared (2D IR) vibrational echo experiments using the heme-bound CO as the vibrational probe. Depending on the temperature, the stretching mode of CO shows two distinct bands corresponding to the native and unfolded proteins. As the temperature is increased from low temperature, a new absorption band for the unfolded protein grows in and the native band decreases in amplitude. Both the temperature-dependent circular dichroism and the IR absorption area ratio R(A)(T), defined as the ratio of the area under the unfolded band to the sum of the areas of the native and unfolded bands, suggest a two-state transition from the native to the unfolded protein. However, it is found that the absorption spectrum of the unfolded protein increases its inhomogeneous line width and the center frequency shifts as the temperature is increased. The changes in line width and center frequency demonstrate that the unfolding does not follow simple two-state behavior. The temperature-dependent 2D IR vibrational echo experiments show that the fast dynamics of the native protein are virtually temperature independent. In contrast, the fast dynamics of the unfolded protein are slower than those of the native protein, and the unfolded protein fast dynamics and at least a portion of the slower dynamics of the unfolded protein change significantly, becoming faster as the temperature is raised. The temperature dependence of the absorption spectrum and the changes in dynamics measured with the 2D IR experiments confirm that the unfolded ensemble of conformers continuously changes its nature as unfolding proceeds, in contrast to the native state, which displays a temperature-independent distribution of structures.

Thermal strains in passivated aluminum and copper conductor lines

Abstract

Accurate measurement of very small line patterns in critical dimension scanning electron microscopy using model-based library matching technique

Our purpose is to reduce the critical dimension (CD) bias for very small patterns with line widths of <15 nm. The model-based library (MBL) method, which estimates the dimensions and shape of a target pattern by comparing a measured scanning electron microscopy image waveform with a library of simulated waveforms, was modified in two ways. The first modification was the introduction of line-width variation into the library to overcome problems caused by significant changes in waveform due to changes in both sidewall shape and line width. The second modification was the fixation of MBL tool parameters to overcome problems caused by the reduction in pattern shape information due to merging of right and left white bands. We verified the effectiveness of the modified MBL method by applying it to actual silicon patterns with line widths in the range 10-30 nm. The CD bias measured by MBL method for three heights (20, 50, and 80%) was consistent with the atomic force microscopy results. The CD biases at all heights were <0.5 nm, and the slopes of the CD biases with respect to the CD were <3%.

Fabrication of seamless three-dimensional roll mold using direct electron-beam writing on rotating cylindrical substrate

A three-dimensional (3D) seamless roll mold is difficult to fabricate because of its cylindrical shape. However, seamless 3D nanoscale patterns are in great demand for optical film applications and printed electronics. The authors have therefore developed a method for producing a 3D seamless roll mold by direct electron-beam (EB) writing onto a layer of resist material coated on a cylindrical substrate that is rotating in a vacuum. In addition, the 3D shape is produced by using the EB dose change method and the controlled-acceleration-voltage electron beam lithography (CAV-EBL) method developed by the authors. In the case of the EB dose change method, hydrogen silsesquioxane (HSQ), which is a negative-type EB resist, was used for the 3D roll mold. In the case of CAV-EBL, spin on glass, which is a positive-type EB resist, was used for the 3D roll mold. As a result, the developed HSQ height can be controlled by changing the EB dose; however, the dose change also causes a line width change. On the other hand, in the CAV-EBL method, the EB dose and acceleration voltage can be used to control the line width and depth independently; therefore, this method can successfully fabricate the coveted 3D roll mold.

Paramagnetic Centres in Oxidised Coal

This paper comprises the results obtained by continuous wave (cw)/pulse electron paramagnetic resonance spectroscopy for oxidised coals. The values of EPR linewidths are dierent for samples of coal treated by dierent chemical agents. The asymmetric EPR line shape indicates to complex composition of paramagnetic centres in coal. In coal oxidised by HNO3 big changes of linewidth with temperature were observed. For all samples the spin‐lattice relaxation time T1 was determined by pulse EPR method. The correlation between used chemical agents and the value of T1 was established.

Investigation of inter-molecular hydrogen bonding in the binary mixture (acetone + water) by concentration dependent Raman study and ab initio calculations

This paper reports that vibrational spectroscopic analysis on hydrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water complexes with changing water concentrations. The optimised geometries and wavenumbers of the neat acetone molecule and its complexes are calculated by using ab initio method at the MP2 level with 6–311+G(d,p) basis set. Changes in wavenumber position and linewidth (fullwidth at half maximum) have been explained for neat as well as binary mixtures with different mole fractions of the reference system, acetone, in terms of intermolecular hydrogen bonding. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the concentration dependent changes in the spectral features in terms of hydrogen bonding.

Molecular interactions between cereal soluble dietary fibre polymers and a model bile salt deduced from 13C NMR titration

Soluble dietary fibres (SDF) such as (1,3:1,4)-beta- d-glucan (βG) and arabinoxylan (AX) have been reported to lower plasma cholesterol levels in the human body, at least in part by preventing bile salts (BS) from being reabsorbed into the enterohepatic circulation. The mechanism(s) by which SDF interact with BS in the digestive tract is not known. This report describes investigations of molecular interactions between a model bile salt (taurochenodeoxycholate – TCDC) micelle with each of βG and AX using 13C NMR. In the presence of βG, chemical shift changes were observed for many bile salt resonances, but not βG resonances, without any apparent change in line widths. In contrast, in the presence of AX, no consistent chemical shift changes were observed for either TCDC or AX resonances, but TCDC signal intensities were reduced. This was not due to simple viscosity effects as the viscosity of the βG used was greater than that of the AX. The results suggest two different mechanisms of interaction between cereal non-starch polysaccharides and TCDC micelles: βG interacts directly on a molecular length scale with the micelles, whilst AX changes the local environment, resulting in reduced micellar mobility without direct molecular interaction.

Modification of edge mode dynamics by oxidation in Ni80Fe20 thin film edges

We use “edge mode” ferromagnetic resonance to probe the magnetic properties of oxidized Ni80Fe20 (Py) nanostripe edges. The oxidation is carried out using either oxygen plasma or thermal annealing in an oxygen ambient. We find that for both treatments the edge saturation field decreases systematically with increasing oxidation due to reduced magnetization near the edges. However, the change of effective out-of-plane anisotropy field shows opposite trends for these two oxidation methods. Micromagnetic simulations suggest that thermally annealed samples may have an additional reduction in the bulk magnetization, possibly due to a compositional change in Py stripes. The two distinct oxidation profiles also result in different changes in resonance linewidth; we find little damping change for plasma treatment but an enhanced effective damping for thermal annealing.

Spin dynamics of S = 1/2 kagome lattice antiferromagnets observed by high‐field ESR

AbstractDue to the existence of strong spin frustration in a system, the spin dynamics of S = 1/2 kagome lattice antiferromagnet at low temperature has attracted much interest. High‐field ESR has been measured on its model substances, Cu3V2O7(OH)2 · 2H2O (volborthite) and BaCu3V2O3(OH)2 (vesignieite), down to 1.8 K using pulsed magnetic fields up to 16 T. The measurements are performed for 160 and 315 GHz using polycrys‐talline samples. Although both samples showed the g‐shift and the change of linewidth at low temperature, volborthite showed a small gap excitation of the order of 40 GHz (1.9 K) while vesignieite showed a paramagnetic behavior down to 1.9 K. Observed difference will be discussed in connection with the crystal structure, and the possible spin liquid state in vesignieite will be discussed.

Exploring Electron Spin−Spin Interactions of Paramagnetic Iron and Radical Cations of Bacteriochlorophyll from Oxidized LH1 in the Presence of Electron Transfer in the Frozen State

Cation free radicals of bacteriochlorophyll (BChl(+)) are formed in the light harvesting complex 1 (LH1) of photosynthetic bacteria upon oxidation by potassium ferricyanide. Unusually narrow EPR line widths are observed for BChl(+) in the frozen state. These narrow line widths are consistent with a molecular-wire behavior where rapid electron/hole transfer occurs between the BChl constituents of the pigment array responsible for light harvesting in bacterial photosynthesis. However, in addition to electron/hole transfer, two distinct types of spin-spin exchange could contribute the EPR line width narrowing, thus obfuscating the determination of LH1 as a molecular wire. First, because excess ferricyanide ion is always present during the EPR measurements, electron spin-spin interactions between the paramagnetic ferricyanide and BChl(+) could be a major source of the EPR line width changes previously attributed solely to electron/hole hopping within the array of BChl molecules in a LH1 unit. Fixing the potential of the ferricyanide/ferrocyanide redox couple gives a constant concentration of paramagnetic iron as the amount of BChl oxidized in LH1 changes. As long as the fraction of oxidized BChl in LH1 remains the same, the EPR line width is found independent of the concentration of the ferricyanide oxidant. Additionally, the trend in EPR line width as a function of temperatures depends only on the fraction of oxidized BChl and not on the concentration of ferricyanide ion. Second, spin-spin exchange interactions between BChl(+)s within LH1 rings could also change the EPR line width. Using LH1 preparations containing at most a few BChl cations per LH1 complex also eliminates the occurrence of significant electron spin-spin exchange as a cause of the observed line width narrowing in minimally oxidized LH1. This investigation of the two types of electron spin-spin exchange interactions demonstrates (1) that electron/hole hopping can take place in oxidized LH1 without involvement of paramagnetic ferricyanide or spin-spin exchange between BChl(+)s and (2) that LH1 maintains a molecular-wire nature at cryogenic temperatures.

Temperature-Dependent Raman Study of the Smectic to Nematic Phase Transition and Vibrational Analysis Using Density Functional Theory of the Liquid Crystalline System 4-Decyloxy Benzoic Acid

Room-temperature Raman spectra of the thermotropic liquid crystalline system, 4-decyloxy benzoic acid (4DBA) have been recorded and the experimentally observed bands are assigned by density functional theory (DFT) for the first time. The C-O and C-C stretching and C-H in-plane bending modes of the phenyl ring and C=O stretching modes of the -COOH group are the marker bands for the smectic (S) --> nematic (N) and nematic (N) --> isotropic (I) transitions for this system. The temperature-dependent Raman spectra for these bands in the heating cycle clearly characterize the S-->N and the N-->I transition over a range <1 degree C, which is much better than the earlier range of 23 degrees C for S-->N and 26 degrees C for the N-->I transition. The approximately 773, approximately 807, approximately 881, and approximately 1146 cm(-1) bands disappear, whereas a band at approximately 830 cm(-1) appears at the S-->N transition. The relative intensity of the approximately 1257 and approximately 1280 cm(-1) bands distinguishes the three phases, namely smectic, nematic, and isotropic, in 4DBA. The variation of line width and peak wavenumber of the approximately 1128 and approximately 1168 cm(-1) bands also clearly shows the two transitions. The molecular reorientation at the transition and the effect of local fields present in the liquid crystalline mesophases are also briefly discussed on the basis of changes in intensity, linewidth and peak wavenumber with temperature.

Photoluminescence spectroscopy of the low-density two-dimensional electron system in electric fields

We performed photoluminescence (PL) measurements of the two-dimensional electron system (2DES) in an undoped GaAs quantum well (QW) while controlling the electron density and electric field independently. We compared the PL spectrum at the same electron density but at different electric fields. The PL linewidth changes with electric field at low electron density below 4×1010 cm−2, but does not change with electric field at higher electron density. The sample we used is composed of a metallic mesh front gate with a 500-nm pitch. The phenomena we report here mainly originate from the longitudinal electric field bias and are commonly observed in a different-mesh-size sample.

Anesthetic Binding Sites in the Neuronal N-Acetylcholine Receptor Transmembrane Domain

Neuronal nicotinic acetylcholine receptors (nAChRs) are sensitive to general anesthetics at physiologically relevant concentrations, but the locations and mechanisms of relevant anesthetic interactions are unknown. The interactions of the anesthetics halothane, isoflurane, and ketamine with the transmembrane domains of the human nAChR α4 and β2 subunits were studied using fluorescence spectroscopy and high-resolution solution NMR. The isolated transmembrane domains, with the extracellular and intracellular domains removed by mutagenesis, were expressed in E. coli and purified into detergent micelles. Multi-angle light scattering experiments on a mixture of α4 and β2 subunits demonstrated their interaction in detergent micelles. Anesthetics quenched the intrinsic tryptophan fluorescence of these proteins in a manner consistent with specific binding. Direct interaction with anesthetic halothane, isoflurane, and ketamine was confirmed by NMR saturation transfer difference spectroscopy. The anesthetics induced chemical shift changes for specific resonances in the NMR spectra of the α4 and β2 transmembrane domains. Two specific interaction sites for the volatile anesthetics halothane and isoflurane have been identified at the extracellular and intracellular interfaces near the ends of the transmembrane domain in the α4 subunit. Differing from halothane and isoflurane, the intravenous anesthetic ketamine affected a set of residues at a more interior location near the extracellular interface. Changes in NMR peak intensity and line width indicated modulations of protein motion by all three anesthetics. This study demonstrated that general anesthetics interact at specific sites within the isolated transmembrane domain of nAChR and affect protein dynamics on a time scale consistent with protein function. This work was supported by NIH grants: R01GM066358, R01GM056257, R37GM049202, and R01GM069766.

Crystal → nematic phase transition in the liquid crystalline system 1‐isothiocyanato‐4‐(trans‐4‐propylcyclohexyl) benzene (3CHBT) probed by temperature‐dependent micro‐Raman study and DFT calculations

AbstractRaman spectra of 3CHBT in unoriented form were recorded at 14 different temperature measurements in the range 25–55 °C, which covers the crystal → nematic (N) phase transition, and the Raman signatures of the phase transition were identified. The wavenumber shifts and linewidth changes of Raman marker bands with varying temperature were determined. The assignments of important vibrational modes of 3CHBT were also made using the experimentally observed Raman and infrared spectra, calculated wavenumbers, and potential energy distribution. The DFT calculations using the B3LYP method employing 6‐31G functional were performed for geometry optimization and vibrational spectra of monomer and dimer of 3CHBT. The analysis of the vibrational bands, especially the variation of their peak position as a function of temperature in two different spectral regions, 1150–1275 cm−1 and 1950–2300 cm−1, is discussed in detail. Both the linewidth and peak position of the (CH) in‐plane bending and ν(NCS) modes, which give Raman signatures of the crystal → N phase transition, are discussed in detail. The molecular dynamics of this transition has also been discussed. We propose the co‐existence of two types of dimers, one in parallel and the other in antiparallel arrangement, while going to the nematic phase. The structure of the nematic phase in bulk has also been proposed in terms of these dimers. The red shift of the ν(NCS) band and blue shift of almost all other ring modes show increased intermolecular interaction between the aromatic rings and decreased intermolecular interaction between two NCS groups in the nematic phase. Copyright © 2009 John Wiley &amp; Sons, Ltd.

EUV pattern defect detection sensitivity based on aerial image linewidth measurements

As the quality of EUV-wavelength mask inspection microscopes improves over time, the image properties and intensity profiles of reflected light can be evaluated in ever-greater detail. The SEMATECH Berkeley Actinic Inspection Tool (AIT) is one such microscope, featuring mask resolution values that match or exceed those available through lithographic printing in current photoresists. In order to evaluate the defect detection sensitivity of the AIT for dense line patterns on typical masks, the authors study the linewidth roughness (LWR) on two masks, as measured in the EUV images. They report the through-focus and pitch dependence of contrast, image log slope, linewidth, and LWR. The AIT currently reaches LWR 3σ values close to 9nm for 175nm half-pitch lines. This value is below 10% linewidth for nearly all lines routinely measured in the AIT. Evidence suggests that this lower level may arise from the mask’s inherent pattern roughness. While the sensitivity limit of the AIT has not yet been established, it is clear that the AIT has the required sensitivity to detect defects that cause 10% linewidth changes in line sizes of 125nm and larger.

Raman scattering study of theFe1−xCoxSb2andFe1−xCrxSb2(0≤x≤1)single crystals

Polarized Raman scattering spectra of the ${\text{Fe}}_{1\ensuremath{-}x}{\text{Co}}_{x}{\text{Sb}}_{2}$ and ${\text{Fe}}_{1\ensuremath{-}x}{\text{Cr}}_{x}{\text{Sb}}_{2}$ $(0\ensuremath{\le}x\ensuremath{\le}1)$ single crystals are measured at room temperature in the $80--200\text{ }{\text{cm}}^{\ensuremath{-}1}$ wavenumber range. All six Raman-active modes, predicted by factor-group analysis, are experimentally observed and assigned. We also analyzed energy and linewidth changes for all six Raman-active modes caused by doping.

Carbon covered magnetic nickel nanoparticles embedded in PBT-PTMO polymer: Preparation and magnetic properties

Abstract Fine particles of a face-centered-cubic phase of Ni covered with a graphite layer were prepared and embedded in a PBT-block-PTMO polymer at a concentration of 0.1 wt%. The mean crystalline size of Ni varied from 8 to 30 nm. A magnetic resonance study of the obtained nanocomposites was carried out in the 4–300 K temperature range using an electron paramagnetic resonance spectrometer. An almost symmetrical and very intense magnetic resonance line was recorded for all the investigated samples. The resonance line was centered at g = 2.253(2) (the resonance field H r = 3003(1) Gs) and had a peak-to-peak linewidth ΔH pp = 693(2) Gs at room temperature. The amplitude of the resonance line increased with a temperature increase in the low temperature range ( T T > 100 K) but was constant at intermediate temperatures. The resonance field H r decreased and linewidth ΔH pp increased as the temperature decreased from room temperature what was similar to the changes observed for other systems of nanoparticles. The thermal gradient of the resonance field, ΔH r / ΔT , strongly depended on the temperature range. The temperature shift of the resonance field and the linewidth were analyzed in terms of the demagnetizing fields of nonspherical agglomerates. A strong change of linewidth and resonance field was registered below 40 K due to the freezing of the spin system’s dynamical magnetic fluctuations. A comparison was made of the results obtained on the Ni/C with the previous measurements on γ-Fe 2 O 3 nanoparticles embedded in a copolymer.

FT-IR, ESI and EPR studies of a Dy(III) Schiff base podand complex

IR spectroscopic, electrospray ionization mass spectrometry, structure and magnetic properties of a dysprosium(III) macroacyclic tripodal Schiff base tris((2-(5-chlorosalicylideno)amino)ethyl)amine (tren-5Clsal) complex are reported. The positions of v(C=N) stretching bonds indicate that the azomethine group nitrogen is coordinated to the rare earth ion. Two main spectral components are observed in the low magnetic field region (<300 mT) in the EPR spectra, independently of temperature. These components are attributed to the Dy 3+ ion with an effective spin of S= 1/2. The magnetic anisotropy between 3 and 23 K is practically constant as evidenced only by a marginal change of the spread of g-factors. The g y -factor increases strongly with an increase in temperature above 23 K, giving rise to a very high magnetic anisotropy of the complex. Such behavior of the magnetic anisotropy at a higher temperature could be an effect of the existence of an excited doublet. A very small value of the Curie-Weiss constant and the lack of any meaningful thermal changes of linewidths indicates the absence of any significant interactions between D y (III) complexes below 20 K. The temperature dependence of the total integrated intensity above 20 K indicates the existence of an excited doublet, occurring about 33(1) K above the ground state.

High-Contrast Grating VCSELs

Recent advances in a single-layer 1-D high-index-contrast subwavelength grating structure are reviewed. Its incorporation into a vertical-cavity surface-emitting laser (VCSEL) structure enabled simple fabrication, lithographically defined polarization control and large aperture, single-transverse-mode control. Extraordinarily large fabrication tolerance is demonstrated with plusmn20% variation of the high-contrast grating (HCG) critical dimension. Emission wavelength of HCG-VCSEL varied 0.2% with a 40% change in lithography linewidth. Tunable VCSELs are fabricated using HCG, which led to a 8000 times reduction in the tunable mirror size and 160 times improved tuning speed of 63 ns. This configuration will open the door for a wide spectrum of optoelectronic devices in large wavelength regimes.