Self-assembled Nanowire Arrays Research Articles

Ultra-high resolution position sensors with self-assembled nanowire arrays

High-resolution position sensor with integrating self-assembled, half-dimensional zinc oxide nanowires as nanopixels.

Self-assembled nanowire arrays as three-dimensional nanopores for filtration of DNA molecules.

Molecular filtration and purification play important roles for biomolecule analysis. However, it is still necessary to improve efficiency and reduce the filtration time. Here, we show self-assembled nanowire arrays as three-dimensional (3D) nanopores embedded in a microfluidic channel for ultrafast DNA filtration. The 3D nanopore structure was formed by a vapor-liquid-solid (VLS) nanowire growth technique, which allowed us to control pore size of the filtration material by varying the number of growth cycles. λ DNA molecules (48.5 kbp) were filtrated from a mixture of T4 DNA (166 kbp) at the entrance of the 3D nanopore structure within 1 s under an applied electric field. Moreover, we observed single DNA molecule migration of T4 and λ DNA molecules to clarify the filtration mechanism. The 3D nanopore structure has simplicity of fabrication, flexibility of pore size control and reusability for biomolecule filtration. Consequently it is an excellent material for biomolecular filtration.

The Synthesis of Stochastic Circuits for Nanoscale Computation

Emerging technologies for nanoscale computation such as self-assembled nanowire arrays present specific challenges for logic synthesis. On the one hand, they provide an unprecedented density of bits with a high degree of parallelism. On the other hand, they are characterized by high defect rates. Also they often exhibit inherent randomness in the interconnects due to the stochastic nature of self-assembly. We describe a general method for synthesizing logic that exploits both the parallelism and the random effects. Our approach is based on stochastic computation with parallel bit streams. Circuits are synthesized through functional decomposition with symbolic data structures called multiplicative binary moment diagrams. Synthesis produces designs with randomized parallel components—and operations and multiplexing—that are readily implemented in nanowire crossbar arrays. Synthesis results for benchmarks circuits show that our technique maps circuit designs onto nanowire arrays effectively.

Self-Assembled Nanowire Arrays for Optical Biosensing

not Available.

The Formation of Self-Assembled Nanowire Arrays on Ge(001): a DFT Study of Pt Induced Nanowire Arrays

AbstractNanowire (NW) arrays form spontaneously after high temperature annealing of a sub monolayer deposition of Pt on a Ge(001) surface. These NWs are a single atom wide, with a length limited only by the underlying beta-terrace to which they are uniquely connected. Using ab-initio density functional theory (DFT) calculations we study possible geometries of the NWs and substrate. Direct comparison to experiment is made via calculated scanning tunneling microscope (STM) images. Based on these images, geometries for the beta-terrace and the NWs are identified, and a formation path for the nanowires as function of increasing local Pt density is presented. We show the beta-terrace to be a dimer row surface reconstruction with a checkerboard pattern of Ge-Ge and Pt-Ge dimers. Most remarkably, comparison of calculated to experimental STM images shows the NWs to consist of germanium atoms embedded in the Pt-lined troughs of the underlying surface, contrary to what was assumed previously in experiments.

Self-Assembled Nanowire Arrays of Metal–Insulator–Semiconductor Diodes Exhibiting S-Type Nonlinearity

We have electrochemically self-assembled regimented arrays of vertically standing nanowire metal-insulator-semiconductor diodes (MISD) embedded in an insulating matrix. Each diode is a 10-nm-diameter semiconductor (CdS) nanowire in contact with an underlying thin insulator ( ~20 nm thick), flanked by two metal electrodes. The density of these MISD devices exceeds 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The dc current-voltage characteristic of several devices in parallel displays an S-type nonlinearity, typical of an MISD. The negative differential resistance associated with the S-type nonlinearity can have a peak to valley ratio as large as 19:1 at room temperature. Individually, such devices can be used as thyristors, logic switches, and high-frequency oscillators. Collectively, they constitute a system of interacting nonlinear elements that could realize a nanoelectronic neuromorphic network model proposed more than a decade ago.

Wire-size-dependent optical activity in electrochemically self-assembled II–VI semiconductor nanowire arrays

We report a non-monotonic dependence on wire diameter of the change in effective refractive index in electrochemically self-assembled nanowire arrays when illuminated with ultraviolet light. The wires are fabricated by electro-depositing CdS, ZnO and ZnSe in anodic porous alumina templates with 50-, 25- and 10-nm diameter pores. A pump-probe setup in an optical interferometer is used to test the thin film arrays. The observed non-monotonic optical behavior can be attributed to the competing effects of decreasing array filling factor and increasing wire optical activity from quantum confinement with reduction in wire diameter. Electromagnetic wave simulations indicate that changes in the effective permittivity of the individual quantum wires in the array must increase rapidly as wire size decreases. Changes in the real part of the permittivity in 10-nm diameter wires are up to an order of magnitude larger than those in 50-nm diameter wires.

The effect of stationary ultraviolet excitation on the optical properties of electrochemically self-assembled semiconductor nanowires

The optical behavior of electrochemically self-assembled nanowire arrays excited by stationary ultraviolet light is investigated. The wires are fabricated by electrodepositing CdS, ZnO, and ZnSe in anodic porous alumina templates with 50, 25, and 10nm diameter pores. We have developed a theoretical model to calculate nanowire permittivity, refractive index, and absorption coefficient under such stationary excitation. This model is incorporated in an electromagnetic wave simulation to obtain the optical response of the array of wires. The behavior is also investigated experimentally using a pump-probe excitation scheme in an optical interferometer. We report a strong nonmonotonic optical activity as a function of wire diameter in the nanowire arrays. This result implies a sharp increase in the optically pumped change in refractive index and permittivity in narrower nanowires.