Conductance through chains of Ge/Si quantum dots: crossover from one-dimensional to quasi-one-dimensional hopping

Parallel chains of germanium quantum dots were grown on a patterned silicon (100) substrate prepared by the combination of nanoimprint lithography and ion irradiation. Strong anisotropy of the conductance between the direction of the chains and the perpendicular one was observed; the current-voltage curves being essentially superlinear. At low bias voltage dependence of the conductance obeys the Arrhenius law indicating one-dimensional (1D) hopping. With increase of the bias this dependence crosses over to $G\propto \exp [-(T_0/T)^{1/2}]$ explained by a quasi-1D transport involving hopping between nearest neighboring chains.