Semiconducting nanowires and nanotubes are an emerging class of 1D nanostructures that represent attractive building blocks for nanoscale electronic and photonic devices. For example, inorganic semiconductor nanowires [1][2][3] and carbon nanotubes, [4] show great promise for nanoelectronic devices and integrated nanosystems because they can function both as device components for logic, memory, and sensing applications and also as interconnects. Inorganic semiconductor nanowires are also attracting increasing research interest as building blocks for integrated nanophotonic systems, since they can function as subwavelength optical waveguides, emissive devices, and photodetectors. [1][2][3][5][6][7][8][9][10][11][12] With respect to the latter, photoconductance measurements have recently been reported for a range of single inorganic nanowire devices: InP, [5] ZnO, [6] GaN, [7] and Si, [8] as well as for carbon-nanotube devices.[13]While inorganic nanowires and carbon nanotubes have been explored in depth, the challenge of controlled fabrication of 1D nanostructures based on organic molecular materials suitable for integrated (opto)electronic applications has yet to be as comprehensively addressed. In particular, semiconducting polymers are attractive materials due to their chemically tunable optical and electronic properties, as well as their facility for solution processing. [14,15] 1D nanostructures fabricated from such polymers have been the subject of recent research with regard to their physical, chemical, electronic, and photonic properties. [16][17][18][19][20] However, demonstration of viable polymer nanowire technologies will require the development of reliable methods for the production of such structures with good control over critical parameters such as diameter, length, morphology, and chemical composition. Recently, a new method for the formation of organic nanotubes and nanowires through the wetting of porous anodized alumina membranes has been reported. [20] This method of template wetting using solution-based or molten material does not require specialized apparatus and is broadly applicable across a wide range of organic materials, including small molecules, oligomers, polymers, blends, and multicomponent solutions.[20]In this work, we demonstrate that solution-assisted template wetting may be successfully exploited for high-yield controlled synthesis of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(bithiophene)] (F8T2) nanowires. Following liberation from the template and dispersion, our method produces discrete nanowires with average lengths of 15 lm and mean diameters of 200 nm. We report on the electrical characteristics of singlenanowire devices and, further, on the use of single F8T2 nanowires in photoconductivity-based photodetectors. To date, there have been relatively few reports on photoconductivity in 1D polymer nanostructures; for example, Kim and coworkers have reported photoconductance in single bilayer nanotubes comprising poly-(p-phenylenevinylene) (PPV) nanotube cores and carbonized PP...

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We report on the synthesis of semiconducting mesowires from regioregular poly(3hexylthiophene) via melt injection into a porous alumina template. Following liberation from the template, mesowires with diameters y450 nm and average lengths of 10 mm were obtained. For two-terminal electrical contacting of individual mesowires on insulating substrates, the drain electrode was formed by shadow masking and metal evaporation, and a conducting probe atomic force microscope tip was employed as the source electrode. This approach enabled combined topographic imaging and spatially resolved electrical characterisation of individual mesowires, allowing the intrinsic mesowire resistivity (700 ¡ 300 V m) as well as the contact resistance (10 ¡ 6 GV) to be estimated. Fitting the measured data to a thermionic emission-diffusion model yielded a hole mobility y2 6 10 25 cm 2 V 21 s 21 and a metal-polymer interface barrier height y0.1 eV.

There is a growing research interest in metal and semiconductor nanocrystals, often termed "artificial atoms", due to their size-dependent optical and electronic properties, such as quantum confinement and single-charge tunneling. [1,2] The development of a detailed understanding of the chargeinjection, retention, and transport properties of individual nanocrystals and nanocrystal arrays is an essential prerequisite if these zero-dimensional (0D) nanostructures are to fulfill their promise as functional elements in future electronic or photonic devices. For example, nanocrystals have been proposed as charge-storage elements in floating-gate flash memories [3] and as quantum dots in photonic devices. [4] While conventional current-voltage measurements on nanocrystal arrays are valuable and provide insight into the mechanisms underlying charge transport and the dimensionality of the current-carrying network, typically they only probe the global properties of the entire array. [5] Little information is revealed about the local charging environment of the nanocrystals. In this regard, scanning-probe methods such as scanning tunneling spectroscopy (STS), electrostatic force microscopy (EFM), and conducting-probe atomic force microscopy (CP-AFM) have recently emerged as effective techniques for combined imaging and local electrical characterization with high spatial resolution. [6,7] These meth-ods have been applied to investigate charging, discharging, and transport mechanisms in individual metal and semiconductor nanocrystals at the single-charge level [8][9][10][11][12][13] and have also been employed to probe the collective electronic properties of nanocrystal arrays. [11,12,[14][15][16][17][18] As the electronic properties of individual nanocrystals are critically dependent on the nanocrystal core diameter, chemically synthesized nanocrystals attract considerable research interest due to the recent emergence of efficient methods for the synthesis of ligand-passivated metal and semiconductor nanocrystals with narrow core size distributions. [1,2] Of these, 28-kDa nanocrystalline gold molecules, containing % 140 gold atoms, have received particular attention. [2] Extensive structural, optical, and electrochemical characterization of these nanocrystal molecules has been undertaken by the research groups of Murray and Whetten. [2,10,11,[19][20][21][22] Due to the small effective diameter of the nanocrystal cores (d % 1.65 nm) and the insulating nature of the protecting ligand monolayer, which acts as a tunnel barrier, single-electron charging effects (Coulomb blockade) have been observed at room temperature in isolated nanocrystals by using STS. [11] Ensemble Coulomb staircases have also been observed at room temperature by electrochemical techniques. [10] Here, we describe the local mapping of the electronic properties of arrays of 28-kDa gold nanocrystals via combined CP-AFM and displacement-voltage (z-V) spectroscopy. Alvarado and co-workers previously used ultrahighvacuum scanning tunneling microscopy (STM) to ...

Redmond and co‐workers report on p. 2379 the successful application of solution‐assisted template wetting to the high‐yield controlled synthesis of poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐(bithiophene)] (F8T2) nanowires (main picture and lower inset). Photoconductivity measurements (schematic in center) yield single‐nanowire device responsivities of ca. 0.4 mA W–1 and external quantum efficiencies of ca. 0.1 % under monochromatic illumination, comparable with data reported for single inorganic nanowire devices.