Thermally activated conductivity and current-voltage characteristic of dielectric phase in granular metals

Abstract

Models of thermally activated linear and high-field nonlinear conductivity of a dielectric phase in granular metals (nanocomposites), i.e., aggregates of small metallic grains in a dielectric matrix, have been suggested. Given a sufficiently large spread of grain sizes, the temperature dependence of the nanocomposite conductivity should be described by a universal “power-1/2” law: G∝exp[−(T 0/T)1/2]. An analytical expression for T 0 has been obtained. It is found that there are two regimes of nonlinear conductivity in a high electric field, namely, a low-field regime, when both the number and mobility of carriers change with the field strength, and a high-field regime, when only the mobility of carriers is variable. Analytical expressions for the nonlinear conductance in both regimes have been obtained.