The temperature-induced transition from 3d to 1d hopping conduction in porous amorphous

Abstract

We have investigated variable-range hopping conduction in amorphous (c = 4 and 7 at.%) samples obtained by ion implantation and treatment by anodic etching in HF solution - porous silicon. As temperature is reduced, we find a crossover from the Mott form to a simply activated law, . This behaviour is attributed to a temperature-induced transition from 3d to 1d hopping conduction in a network of weakly interconnected silicon quantum `wires'. The mean diameter of the silicon wires, D = 5 - 6 nm, was deduced from analysis of the conductivity data and is in agreement with XTEM and STM observations. It was found that the density of states in the porous material is smaller than in the compact material due to broadening of the impurity band caused by lateral confinement in the silicon wires.

The Kondo effect in amorphous

“…Values of F and g( F ) were set before fitting and the best fits then yielded values for ρ 0 , ρ 1 and J which are summarized in table 2. Here we used m * = 0.4m 0 (Yakimov et al 1996) and n is twice the Mn concentration (corresponding to a valence of 2). Clearly, the magnitude obtained for the exchange integral, J ≈ −0.45 eV, is quite reasonable and supports our interpretation.…”