Controlling the morphology of soluble small molecule organic semiconductors is crucial for the application of such materials in electronic devices. Using a simple dip-coating process we systematically vary the film drying speed to produce a range of morphologies, including oriented needle-like crystals. Structural characterization as well as electrical transistor measurements show that intermediate drying velocities produce the most uniformly aligned films.

This review is intended as an introduction to mesomagnetism, with an emphasis on what the defining length scales and their origins are. It includes a brief introduction to the mathematics of domains and domain walls before examining the domain patterns and their stability in 1D and 2D confined magnetic structures. This is followed by an investigation of the effects of size and temperature on confined magnetic structures. Then, the relationship between mesomagnetism and the developing field of spin electronics is discussed. In particular, the various types of magnetoresistance, with an emphasis on the theory and applications of giant magnetoresistance and tunnelling magnetoresistance, are studied. Single electronics are briefly examined before concluding with an outlook on future developments in mesomagnetism.

A comparison of four different methods to make electrical contact to both 100nm gold nanowires and 50nm multiwall carbon nanotubes is given. The techniques are compared in terms of the success yield, contact resistance, complexity of the fabrication steps, and potential for creating novel device structures and architectures. The different methods compared are (i) in situ micromanipulation of wires onto prepatterned electrodes, (ii) ion and electron beam assisted deposition, (iii) electron beam lithography, and (iv) drop casting of wires from solution onto prepatterned electrodes.

We present an analysis of spin injection efficiency that is of general application and relevant to a wide range of spin-electronic devices. By applying simple band structure ideas to a single interface between a metallic ferromagnet and a three-dimensional semiconductor, two conflicting figures of merit are identified - spin accumulation and polarization of injected current - and their validity to the analysis of different device types is discussed. The injected spin accumulation is smaller than the all-metal injection case by a factor (m*/me)3/2(kT/EF)1/2e^εD/kT. Moreover, the injected spin current at the interface is reduced by the factor (m*/me)3/2(kT/EF)(γS/γF) e^εD/kT, where γ for a particular material is the square root of its momentum scattering to spin-flip scattering ratio, m* and me are the effective and free masses, respectively, and εD is the donor binding energy. These results are consequent on the boundary condition that the spin channel electrochemical potentials are continuous at the interface. By inserting an insulating tunnel barrier between the ferromagnet and the semiconductor, not only is this boundary condition removed and the spin polarization of the injected current restored to the all-metal magnitude, but also the spin accumulations in the metal and the semiconductor even have opposite signs. This implies that thin or discontinuous tunnel barriers have the worst spin injection efficiency of any configuration. We finally note that for injected spin current into metals with polarization approaching 100%, the Fermi surface is polarized to a depth which exceeds the equilibrium carrier depth by a factor lSD/λ, hence >>1.

Articles you may be interested inSombrero-shaped Fe3O4 nanoelements with tunable out-of-plane and in-plane magnetization components fabricated by nano-imprint lithography Fabrication of poly(3-hexylthiophene) self-switching diodes using thermal nanoimprint lithography and argon milling J.Comparison of organic diode structures regarding high-frequency rectification behavior in radio-frequency identification tags