Possible origin of the smaller-than-universal percolation-conductivity exponent in the continuum.

For quite a few systems in the continuum, such as carbon nanotube polymer composites and segregated composites, percolation electrical conductivity exponents that are much smaller than the universal value have been reported. This is unexpected in view of the classical lattice percolation theory. Here we provide a simple general phenomenological model that accounts for such observations within the framework of universality.

Si-rich Al2O3 films grown by RF magnetron sputtering: structural and photoluminescence properties versus annealing treatment.

Silicon-rich Al2O3 films (Six(Al2O3)1-x) were co-sputtered from two separate silicon and alumina targets onto a long silicon oxide substrate. The effects of different annealing treatments on the structure and light emission of the films versus x were investigated by means of spectroscopic ellipsometry, X-ray diffraction, micro-Raman scattering, and micro-photoluminescence (PL) methods. The formation of amorphous Si clusters upon the deposition process was found for the films with x ≥ 0.

Low-dimensional effects in a three-dimensional system of Si quantum dots modified by high-energy ion irradiation.

Modification of films containing Si nanocrystallites embedded in SiO2 by irradiation with high-energy ions was found to induce peaks in their low-frequency capacitance-voltage characteristics. Considering the nanocrystallite spatial distribution that follows the ion tracks we interpret these peaks as due to the charge transfer along these tracks, similar to the process that was reported previously for two-dimensional arrays of such crystallites. The ion irradiation of the above three-dimensional system appears to be useful then for the fabrication of nanostructures, which have also the properties of low-dimensional arrays.

The modification of Si nanocrystallites embedded in a dielectric matrix by high energy ion irradiation.

We have followed the effects of heavy ion irradiation on the structural, electrical, and photoluminescence properties of ensembles of silicon nanocrystallites embedded in a dielectric (SiO(2)) matrix. This was done as a function of the irradiation dose and the content of the Si phase. The results obtained can be accounted for self-consistently assuming that a relatively small dose of the irradiation enhances the crystallization while for higher doses the irradiation enhances the amorphization.

Exact phase boundary of an amphiphile-rich phase in a ternary solution on a Bethe lattice.

A model ternary solution is considered in which the bonds of a three-coordinate Bethe lattice are covered by rodlike molecules of types AA, BB, and AB, the AB-type molecule representing an amphiphile. The phase boundary in temperature-composition space of an ordered amphiphile-rich phase is calculated exactly.