Highly ordered hexagonal arrays of parallel metallic nanowires (Ni, Bi) with diameters of about 50 nm and lengths up to 50 μm were synthesized by electrodeposition. Hexagonal-close-packed nanochannel anodized aluminum oxide film was used as the deposition template. The deposition was performed in an organic bath of dimethylsulfoxide with metal chloride as the electrolyte. A high degree of ordering and uniformity in these arrays can be obtained with this technique by fine-tuning the electrodeposition parameters. Moreover, an unprecedentedly high level of uniformity and control of the wire length was achieved. The arrays are unique platforms for explorations of collective behavior in coupled mesoscopic systems, and are useful for applications in high-density data storage, field emission displays, and sensors.

In this work we demonstrate the feasibility of electric-field tuning of the plasmonic spectrum of a novel gold nanodot array in a liquid crystal matrix. As opposed to previously reported microscopically observed near-field spectral tuning of individual gold nanoparticles, this system exhibits macroscopic far-field spectral tuning. The nanodot-liquid crystal matrix also displays strong anisotropic absorption characteristics, which can be effectively described as a collective ensemble within a composite matrix in the lateral dimension and a group of noninteracting individual particles in the normal direction. The effective medium model and the Mie theory are employed to describe the experimental results.

The Cooper pairing mechanism that binds single electrons to form pairs in metals allows electrons to circumvent the exclusion principle and condense into a single superconducting or zero-resistance state. We present results from an amorphous bismuth film system patterned with a nanohoneycomb array of holes, which undergoes a thickness-tuned insulator-superconductor transition. The insulating films exhibit activated resistances and magnetoresistance oscillations dictated by the superconducting flux quantum h/2e. This 2e period is direct evidence indicating that Cooper pairing is also responsible for electrically insulating behavior.

A nonlithographic technique that utilizes highly ordered anodized aluminum oxide porous membrane as template is presented as a general fabrication means for the formation of an array of vastly different two-dimensional lateral superlattices structures. Hexagonal close-packed nanopore arrays were fabricated on Si, GaAs, and GaN substrates via reactive ion etching. Quantum dot arrays of various metals and semiconductors were formed through evaporation and subsequent etching. The two-dimensional lateral superlattice structures fabricated using this method are of a high level of ordering, uniformity, and packing density. The diameter and periodicity of the nanostructures are determined by the features of the original alumina membrane, which can be adjusted by varying the anodization conditions.

Ultrathin amorphous Bi films, patterned with a nano-honeycomb array of holes, can exhibit an insulating phase with transport dominated by the incoherent motion of Cooper Pairs (CP) of electrons between localized states. Here we show that the magnetoresistance (MR) of this Cooper Pair Insulator (CPI) phase is positive and grows exponentially with decreasing temperature, T , for T well below the pair formation temperature. It peaks at a field estimated to be sufficient to break the pairs and then decreases monotonically into a regime in which the film resistance assumes the T dependence appropriate for weakly localized single electron transport. We discuss how these results support proposals that the large MR peaks in other unpatterned, ultrathin film systems disclose a CPI phase and provide new insight into the CP localization.Below its transition temperature, T c0 , a conventional superconductor, like Pb, can be driven into its non-superconducting, normal state by applying a magnetic field, H. The temperature, T , dependent sheet resistance, R (T ), of this state joins smoothly to the normal state resistance just above T c0 , R N , and assumes the dependence expected for a simple metal of unpaired electrons [1]. The behavior of this low T normal state changes substantially when these superconductors are made as thin films with R N ∼ R Q = h/4e2 . For example, applying a H to superconducting (SC) films of either Indium oxide For granular Pb films, the formation of a CPI phase has strong intuitive appeal and experimental support. STM experiments show that they consist of islands of grains that can naturally localize CPs [9]. Indeed, tunneling experiments on insulating films confirmed the existence of these localized pairs by showing the energy gap in the density of states that accompanies CP formation [6]. Also, these insulators exhibit giant negative Magneto-Resistance (MR) that can be attributed to the enhancement of inter-island quasi-particle tunneling [10]. By contrast, InO x and TiN films lack any obvious structure that could localize CPs. Moreover, these films exhibit a giant positive MR [3,4,5,11,12], which can peak orders of magnitude above R N at sufficiently low T . The mechanism behind this spectacular giant positive MR [3,4,5,11,12] and whether it is a property of a CPI phase remains unresolved despite significant attention [13,14,15,16].Theories of the positive MR peak presume that CPs spontaneously localize into islands or puddles [13,14,15,16]. On each island, the complex SC order parameter has a well defined amplitude, but electrostatic interactions between islands prevents the development of the long range phase coherence necessary for CP delocalization. A magnetic field induces more phase disorder and localization through the direct coub.

A uniform array of a new type of heterojunction formed between carbon nanotubes and silicon is studied. The heterojunction array was controllably grown with parallel and uniform nanotubes vertically aligned to the silicon substrate using a self-organized nanopore array template. The pronounced rectifying characteristics of the heterojunction were measured with an on/off ratio as high as 10(5) at 4 V. The analysis shows a large and type-I band offset at the heterojunction. The charge transport in the nanotubes is found to be strongly coupled to and limited by the dielectric charging and polarization in the hosting alumina matrix surrounding the nanotubes.

We describe a strategy that permits discrete regions of arrayed carbon nanotubes (CNTs) to be functionalized simultaneously and specifically with DNA oligonucleotides. The different chemical properties of two regions on single CNTs and orthogonal chemical coupling strategies have been exploited to derivatize CNTs within highly ordered arrays with multiple DNA sequences. Through duplex hybridization, we then targeted different DNA sequences with appended metal nanoparticles to distinct sites on the CNT architecture with precise spatial control. The materials generated from these studies represent the first CNTs with bipartite functionalization. The approach described provides a high level of precision in parallel and directed assembly of DNA sequences and appended cargo and is useful for the preparation of novel hybrid bionanomaterials.

Eddy current pulsed thermography (ECPT) applies induction heating and a thermal camera for non-destructive testing and evaluation (NDT&E). Because of the variation in resultant surface heat distribution, the physical mechanism that corresponds to the general behavior of ECPT can be divided into an accumulation of Joule heating via eddy current and heat diffusion. However, throughout the literature, the heating mechanisms of ECPT are not given in detail in the above two thermal phenomena and they are difficult to be separated. Nevertheless, once these two physical parameters are separated, they can be directly used to detect anomalies and predict the variation in material properties such as electrical conductivity, magnetic permeability and microstructure. This paper reports physical interpretation of these two physical phenomena that can be found in different time responses given the ECPT image sequences. Based on the phenomenon and their behaviors, the paper proposes a statistical method based on single channel blind source separation to decompose the two physical phenomena using different stages of eddy current and thermal propagation from the ECPT images. Links between mathematical models and physical models have been discussed and verified. This fundamental understanding of transient eddy current distribution and heating propagation can be applied to the development of feature extraction and pattern recognition for the quantitative analysis of ECPT measurement images and defect characterization.