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One-dimensional quantum wires are expected to play important role in future electronic and optical devices. We have investigated semiconducting nanowires made by a novel supercritical fluid solution-phase technique [1]. Conductivity and force interactions in individual semiconductor nanowires were investigated by using an in-situ probing technique using a TEM-SPM [2,3], which is a combination of the scanning probe microscope (SPM) and the transmission electron microscope (TEM). Free standing Si nanowires were high resistive with exhibited metallic behaviour. Nonconductive gap was observed in Ge nanowires. The electromechanical properties of these wires were characterised and a prototype nanorelay was demonstrated. Uniform mesoporous thin films, with pores orientated almost perpendicular to the substrate surface are used as templates for unidirectional semiconducting nanowire growth. Structure of films and polycrystalline material containing Si and Ge nanowire arrays was investigated [4]. Luminescence of mesoporous nanowires was determined, as function of nanowire size. The optical properties can be controlled by the effective change of pore size inside mesoporous silica. Quantum-chemical simulation of the silicon nanowires is carried out by semi-empirical CLUSTER code.

In this work we report how single crystal nanowires can be assembled into regular arrays using mesoporous thin films to define the architecture. Mesoporous thin films were prepared by a sol-gel method. These provide films of very regular structure and dimensions. The films produced in this way have almost single crystal like structures and can also exhibit strong epitaxy to the underlying silicon substrate. The films are subjected to a supercritical fluid (SCF) environment in which a precursor is decomposed to yield nanowires of metals, semiconductors or oxides. Using these SCF conditions, pore filling is complete and the products are nanowires which are single crystals and structurally aligned in one direction. The growth mechanism of the nanowires is described and size effects discussed.

Nanoscale gold contacts were investigated both experimentally and theoretically. Simulations of in situ processes in a new combined TEM-AFM microscope were performed by molecular dynamics and theoretical mechanics methods. Atomistic transformations of gold nanometer-sized wires (nanowires) between Au-probe and Au-surface were studied in processes both of loading-unloading and in the normal, lateral, diagonal and zigzag directions of the probe motion. Molecular dynamics was used for studies of "adhesion avalanche", shear and strain deformations. Theoretical mechanics was used for studies of jump-to-contact and jump-off-contact phenomena. Reorientations from (100) to (111) planes with formation of extended zigzag, vacancy cavities, a double-neck creation and a slip along the (110) plane with formation of twins and steps were observed. Deformation mechanisms were shown to depend on schemes of motions and on the ratio between the relative velocity of the probe and surface motion and the velocity of the defect relaxation.

We report a "clean" and fast process, utilizing supercritical carbon dioxide, for producing ultrahigh densities, up to 10(12) nanowires per square centimeter, of ordered germanium nanowires on silicon and quartz substrates. Uniform mesoporous thin films were employed as templates for the nucleation and growth of unidirectional nanowire arrays orientated almost perpendicular to a substrate surface. Additionally, these nanocomposite materials display room-temperature photoluminescence (PL), the energy of which is dependent on the diameter of the encased nanowires. The ability to synthesis ultrahigh-density arrays of semiconducting nanowires on-chip is a key step in future "bottom-up" fabrication of multilayered device architectures for nanoelectronic and optoelectronic devices.