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This research uses spatially resolved electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) to determine an upper bound for the interfacial width of a solution-cast poly(styrene) (PS)−poly(2-vinylpyridine) (PVP) homopolymer blend. The measurement determines the fraction of nitrogen as a function of position across an unstained interface. The broadening effect of the incident-probe intensity distribution is deconvoluted from the raw data. In addition, a lower bound to the contribution of interfacial curvature to the interfacial width is estimated and also separated from the measured data. This leads to an upper bound to the interfacial width of 3.5 nm. The result is in agreement with independent measurements by neutron scattering reported in the literature. Dose-resolved measurements are made to demonstrate that the effects of mass loss during the present measurements are insignificant. Quantitative analysis of the carbon/nitrogen ratio is made on the basis of the background-subtracted C and N K-edges in PVP finding a value of 7.05 ± 0.20, in agreement with the stoichiometric value of 7.0.

The traditional methods for studying polymer microstructure in the transmission electron microscope largely hinge on the use of differential heavy-element staining to induce amplitude contrast. However, adequate staining agents are not available for all polymer systems. Furthermore, nonlinearities in the distribution of stain, particularly at interfaces, degrade the achievable resolution. Spatially resolved electron energy loss spectroscopy (EELS), on the other hand, provides a new opportunity to study polymer microstructure by providing rich spectroscopic features and high spatial resolution. Translating this opportunity into practice is underpinned by three main factors: (1) the availability of spectral fingerprints distinguishing various polymers; (2) the limits of achievable resolution; and (3) the ultimate constraints imposed by electron irradiation. This study discusses these issues and demonstrates the use of spatially resolved EELS with examples from hydrocarbon homopolymer and homopolymer blends of polyphenylene sulfide (PPS) and polyethylene terephthalate (PET), nylon 6/high-density polyethylene (HDPE) and polystyrene/polyethylene (PS/PE).

We report a substantial improvement in the behavior of Josephson junctions scribed in Y1Ba2Cu3O7−δ films using a high-brightness field-emission electron gun source instead of a lower-brightness thermionic source. These junctions exhibit resistively shunted junction behavior over the entire temperature range from the coupling temperature to at least 4 K, a temperature window which can be larger than 55 K. Superconductor-normal-superconductor character is indicated by the exponential dependence of the critical current on temperature for all temperatures below 90 K. The data demonstrate that electron irradiation under these conditions produces a modified region which is completely normal above 4 K and is narrower in width than previously obtained.

We present a detailed characterization of the dynamic properties of proximity-coupled Josephson junctions in YBa2Cu3O7 fabricated by electron-beam scribing. A full description of the low-temperature behavior includes nonequilibrium processes in the normal barrier as well as wide-junction effects resulting from the planar geometry. Above ∼40 K these junctions obey the standard (equilibrium) resistively-shunted junction (RSJ) model in applied magnetic field. At lower temperatures, the volt–ampere V(I) curves develop a temperature-dependent “excess critical current,” saturating at 0.5–0.75 of the total critical current. Below ∼10 K hysteresis is observed. The observed temperature dependence and magnitude of the excess current and hysteresis are qualitatively consistent with published calculations based on the time-dependent Ginzburg–Landau equations. At low temperatures, the V(I) curves in applied field deviate significantly from the RSJ model, which we attribute to wide-junction behavior with a nonuniform bias-current distribution.