Carbon nanotubes (CNTs), standing perpendicularly to a substrate with an electrode, were fabricated by thermal catalytic decomposition of ethylene from Co particles electrochemically embedded at the bottom of anodic alumina nanoholes. The thermal durability of the alumina nanoholes for the CNTs growth process was achieved by using Nb as an underlying electrode. The CNTs were electrically connected to the electrode through the conductive paths, which were formed at the bottom of alumina nanoholes by Nb ion migration from the underlying electrode during anodization.

turn changes the effective contrast between the alternating polymer and LC rich layers in the structure. This is a simple and flexible system by which photoresponsive photonic crystals can be fabricated in a single-step process. In addition to the one-dimensionally periodic systems such as those presented here, complex two-and three-dimensionally periodic HPDLC photonic materials could be fabricated [13] with the Azo-LC materials to make dynamic photonic crystals of any structure in a one-step process. Future studies will include fabricating novel photo-optic photonic structures, in addition to probing the ultimate response time of the system, as well as the effects of excitation intensity, wavelength, and azobenzene concentration. ExperimentalHolographic-polymer-dispersed liquid crystal structures containing azobenzene-derived liquid crystals were prepared from a standard prepolymer syrup containing 35 % E7, to which was added an additional 3.5 % BMAB. The preparation of a standard syrup can be found in [10] and [11], for example. The BMAB was synthesized according to [14], and can be commercially obtained from BEAMCo Inc, Winter Park, FL. Sample cells were prepared by placing a small amount of syrup to which a small amount of 8 lm glass spherical spacers were added on indium tin oxide (ITO) coated glass. The resulting cell contains approximately an 8±10 lm layer of photo sensitive syrup between two glass plates. Bragg reflection gratings were prepared using two counter propagating beams incident on the sample cell. This produced a one dimensionally periodic holographic structure with a grating vector perpendicular to the surface of the cell. The initial diffraction efficiency of these gratings was probed at normal incidence and ranged from 45 to 55 %. Control gratings prepared from an identical syrup without BMAB showed diffraction efficiencies of 50 to 55 %. Current studies in bulk have shown that 10 % BMAB in E7 is sufficient to induce an isothermal N±I transition at room temperature [15]. In order to minimize the attenuation of the triggering UV light through the thickness of the sample, it is desirable to use as low a concentration of Azo-LC as is sufficient to observe a complete, isothermal N±I transition. Thus approximately 3.5 % of the weight of the syrup in BMAB was added to the syrup, which constitutes roughly 10 % of the liquid crystal content. A convenient wavelength, 540 nm, was selected for holographic recording such that it did not overlap the cis absorption substantially, which provided for an accurate measurement of the diffraction efficiency.Once recorded, the reflection gratings are characterized in an apparatus which allowed for the introduction of both a UV laser beam (up to 80 mW cm ±2 of 365 nm from and Ar+ laser) and a doubled Nd:YVO 4 CW beam of 532 nm (up to 100 mW cm ±2 ) while the visible transmission spectrum and absorbance at 365 nm are simultaneously recorded. The UV beam was near the peak absorption of the trans conformer of the Azo-LC and produced a discernable change in color ...

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Ultrahigh pore density nanoporous films with a pore diameter of less than 10nm and a pore density exceeding 1016 pores/m2 were developed. Nano phase separation of a eutectic Al-Si system was used for the fabrication of these nanoporous films. Co-sputtered AlSi films form Al nano-cylinders, perpendicular to the substrate and parallel to each other, embedded in an amorphous Si matrix during film growth due to phase separation. Removal of the Al nano-cylinders from the co-sputtered AlSi films by chemical etching gives us ultrahigh pore density nanoporous films. The nanoporous films consist of mainly oxidized silicon. Depending on the film compositions and the film preparation conditions, such as RF power and the deposition temperature, the average pore diameter can be varied systematically from less than 5nm to 13nm with the pore density from 1015 to exceeding 1016 pores/m2. Furthermore we have demonstrated a template-assisted growth of ultrahigh-density Ni nanowire arrays with an aspect ratio of ∼100 in the nanoporous films by electrodeposition. The fabrication method for nanowire arrays using the nanoporous films is quite simple and promising for the fabrication of nanostructured devices.

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