Angular behavior of the Berreman effect investigated in uniform Al2O3 layers formed by atomic layer deposition.

Experimental transmission absorbance infrared spectra of γ-Al(2)O(3) showing evidence of the angular dependence of the peaks of surface modes appearing next to the longitudinal optical phonon frequency ω(LO) (the Berreman effect) are collected from heat-treated thin oxide films deposited with thickness uniformity on Si(100) using atomic layer deposition. The peak area of the most intense surface longitudinal optical mode is plotted versus the infrared beam incidence angle θ(0). The experimental points closely follow the sin(4)(θ(0)) function in a broad thickness range.

Phonon response in the infrared region to thickness of oxide films formed by atomic layer deposition.

Experimental transmission infrared spectra of gamma-Al(2)O(3) and ZnO films are collected from heat-treated thin oxide films deposited with uniform thickness on Si(100) using atomic layer deposition. We show that the Berreman thickness, i.e.

Atomic layer deposition and abrupt wetting transitions on nonwoven polypropylene and woven cotton fabrics.

Atomic layer deposition (ALD) of aluminum oxide on nonwoven polypropylene and woven cotton fabric materials can be used to transform and control fiber surface wetting properties. Infrared analysis shows that ALD can produce a uniform coating throughout the nonwoven polypropylene fiber matrix, and the amount of coating can be controlled by the number of ALD cycles. Upon coating by ALD aluminum oxide, nonwetting hydrophobic polypropylene fibers transition to either a metastable hydrophobic or a fully wetting hydrophilic state, consistent with well-known Cassie-Baxter and Wenzel models of surface wetting of roughened surfaces.

Surface polarity shielding and hierarchical ZnO Nano-architectures produced using sequential hydrothermal crystal synthesis and thin film atomic layer deposition.

Three-dimensional nanoscale constructs are finding applications in many emerging fields, including energy generation and storage, advanced water and air purification, and filtration strategies, as well as photocatalytic and biochemical separation systems. Progress in these important technologies will benefit from improved understanding of fundamental principles underlying nanostructure integration and bottom-up growth processes. While previous work has identified hydrothermal synthesis conditions to produce nanoscale ZnO rods, sheets, and plates, strategies to systematically integrate these elements into more complex nano-architectures are not previously described.

Real-time conductivity analysis through single-molecule electrical junctions.

Conductance through single-molecule junctions, consisting of nanoparticle/molecule/nanoparticle units between nanoscale planar electrodes, was monitored in real time during several process sequences, including dielectrophoretic directed self-assembly and post-assembly modification. Assembly faults are directly detected in real time when non-ideal assembly conditions result in molecular junction failure and nanoparticle fusion in the junction. The real-time conductivity measured through the junction was sensitive to ambient conditions, and changes persisted over several days of exposure.

Conductivity in alkylamine/gold and alkanethiol/gold molecular junctions measured in molecule/nanoparticle/molecule bridges and conducting probe structures.

Charge transport through alkane monolayers on gold is measured as a function of molecule length in a controlled ambient using a metal/molecule/nanoparticle bridge structure and compared for both thiol and amine molecular end groups. The current through molecules with an amine/gold junction is observed to be more than a factor of 10 larger than that measured in similar molecules with thiol/gold linkages. Conducting probe atomic force microscopy is also used to characterize the same monolayer systems, and the results are quantitatively consistent with those found in the nanoparticle bridge geometry.

Conduction mechanisms and stability of single molecule nanoparticle/molecule/nanoparticle junctions.

Nanoparticle/molecule/nanoparticle dimer assemblies have been successfully trapped by dielectrophoresis across nanogap electrodes, enabling temperature dependent charge transport measurements through an oligomeric phenylene ethynylene molecule, and transition from direct tunnelling to Fowler-Nordheim tunnelling is observed at approximately 1.5 V. Samples formed by dielectrophoresis show better contact stability than those formed by receding meniscus.