Direct liquid crystal templating from non-ionic polyoxyethylene surfactants has been utilised to produce well-defined birefringent films of nanostructured cadmium telluride films which displayed good optical properties as evidenced by UV/VIS reflectance spectroscopy.

a b s t r a c tCurrent transport at Schottky barriers is of particular interest for spin injection and detection in semiconductors. Here, electrodeposited Ni-Si contacts are fabricated and the transport mechanisms through the formed Schottky barrier are studied. Highly doped Si is used to enable tunneling currents. I-V, C-V and low-temperature I-V measurements are performed and the results are interpreted using tunneling theory for Schottky barriers and recent models for spatially distributed barrier heights. It is shown that, contrary to the case of lowly doped Si where thermionic emission dominates, tunneling is the dominant mechanism for reverse and low forward bias for highly doped Si. An exponential reverse bias I-V behavior with negative temperature coefficient is reported. An explanation can be found on the rapid decrease of the reverse bias I-V slope with temperature predicted by Padovani and Stratton for thermionic field emission in conjunction with the increase of the Schottky barrier height with temperature suggested for spatially distributed barrier heights.

Using self-assembly of polystyrene spheres, well-ordered templates have been prepared on glass and silicon substrates. Strong guiding of self-assembly is obtained on photolithographically structured silicon substrates. Magnetic antidot arrays with three-dimensional architecture have been prepared by electrodeposition in the pores of these templates. The shape anisotropy demonstrates a crucial impact on magnetization reversal processes.

We have succeeded in aligning self-assembled structures by using a lithographically defined stripe. The 140 nm wide by 100 nm high SiO 2 strip is shown to guide the assembly of 500 nm latex spheres so that spheres are aligned along the strip and are in registration on either side of the strip. This method can be used to increase long-range ordering in magnetic storage systems without compromising the density. Inverse sphere Ni arrays were made by electrodeposition through the latex template. We also show that the hexagonal symmetry of the resulting inverse sphere Ni arrays can be simulated using the approach presented below. r

Growth of periodic nanoporous CdTe and ZnO metamaterials is developed and characterised. We model the induced birefringence and measure the charge transport and density of surface states in the films.Nanostructuring materials to produce metamaterials with novel and optimised functional properties is a new field which is already showing great promise. One powerful technique to create such metamaterials with new properties is to grow through lyotropic liquid crystals phase which act as nano-templates. The first materials produced using a liquid crystal template method were silica films in 1995 [l], which had structures on the scale of -3mn. Since this time much research has been concentrated in this field, yet surprisingly only a few semiconductors have been templated. We present work on the fabrication of the nanostructured semiconductors cadmium telluride and zinc oxide along with characterisation of their nanostructure-induced birefringence along with a theoretical model which fully explains the observed birefringence. We also present the results of photocurrent spectroscopy and electrical impedance measurements which allow us to quantify charge transport within the films and the density and nature of surface statesThe films are produced using electrochemical deposition techniques where a plating solution is mixed with the self-assembled lyotropic liquid crystal, the film is then potentiostatically deposited onto a conductive electrode as shown in figure 1[2]. After the film is deposited the surfactant columns are removed with solvents. The film that is left after growth is a semiconductor film containing a hexagonal array of cylindrical air pores with pore diameters -3nm and a separation of -6nm which have a range of thickness (0.1-Ipm) depending on growth time. Surfactant Semiconductor * l l :G~~~rowth Conductive ___!__ !_20nm _Substrate -20nm Fig. 1. Representation of liquid crystal nano -template at the surface of an electrode. Growth occurs from the aqueous phase surrounding the surfactant columns producing a semiconductor containing a hexagonal array of pores at an angle 0.To determine the existence of nanostructuring we employ two main techniques, low angle x-ray diffraction and transmission electron microscopy [2], both giving information about the pore separation with the latter also giving information about the pore diameter. These nanostructured semiconductor metamaterials have new and enhanced properties, one being their giant form birefringence (-4%), which is purely due to the anisotropic nanostructuring imposed on the film. The birefringence of the CdTe, which in its bulk form is isotropic, is clearly observed using polarised optical microscopy with the images seen directly comparable to those seen in the template mixture alone. To quantify the birefringence the anisotropic spectral dependence of individual domains (up to 0. Imm2) has been determined using normal incidence micro-reflectivity experiments with polarised illumination, unpolarised detection, and rotation of the sample in the azimuthal...