Influence of Structure on Electronic Charge Transport in 3D Ge Nanowire Networks in an Alumina Matrix.

We demonstrate formation of material consisting of three-dimensional Germanium nanowire network embedded in an insulating alumina matrix. A wide range of such nanowire networks is produced using a simple magnetron sputtering deposition process. We are able to vary the network parameters including its geometry as well as the length and width of the nanowires. The charge transport in these materials is shown to be related to the nanowire surface per unit volume of the material, α. For low values of α, transport is characterized by space charge limited conduction and a drift of carriers in the extended states with intermittent trapping-detrapping in the localized states. For large values of α, charge transport occurs through hopping between localized electronic states, similar to observations in disorder-dominated arrays of quantum dots. A crossover between these two mechanisms is observed for the intermediate values of α. Our results are understood in terms of an almost linear scaling of the characteristic trap energy with changes in the nanowire network parameters.

Preparation of non-oxidized Ge quantum dot lattices in amorphous Al2O3, Si3N4 and SiC matrices.

The preparation of non-oxidized Ge quantum dot (QD) lattices embedded in Al2O3, Si3N4, SiC matrices by self-assembled growth was studied. The materials were produced by magnetron sputtering deposition, using different substrate temperatures. The deposition regimes leading to the self-assembled growth type and the formation of three-dimensionally ordered Ge QD lattices in different matrices were investigated and determined. The oxidation of the Ge QDs in different matrices was monitored and the best conditions for the production of non-oxidized Ge QDs were found. The optical properties of the Ge QD lattices in different matrices show a strong dependence on the Ge oxidation and the matrix type.

Temperature behaviour of the average size of nanoparticle lattices co-deposited with an amorphous matrix. Analysis of Ge + Al2O3 and Ni + Al2O3 thin films.

We theoretically interpret the thermal behaviour of the average radius versus substrate temperature of regular quantum dot/nanocluster arrays formed by sputtering semiconductor/metal atoms with oxide molecules. The analysis relies on a continuum theory for amorphous films with given surface quantities, perturbed by a nanoparticle lattice. An account of the basic thermodynamic contributions is given in terms of force-flux phenomenological coefficients of each phase (Ge, Ni, Al2O3). Average radii turn out to be expressible by a characteristic length scale and a dimensionless parameter, which mainly depend upon temperature through diffusion lengths, film pressures and finite-size corrections to interfacial tensions. The numerical agreement is good in both Ge ([Formula: see text]) and Ni ([Formula: see text]) lattices grown at temperatures [Formula: see text]800 K, despite the lower temperature behaviour of quantum dots seeming to suggest further driving forces taking part in such processes.