The transition from two- to one-dimensional electronic transport in narrow silicon accumulation layers

Preliminary results of the temperature and magnetic field dependence of the conductivity of narrow silicon accumulation layers are presented. Channels approximately 1 mu m wide at temperatures T approximately 1K exhibit positive magnetoconductance and Shubnikov-de Haas oscillations characteristic of weakly localised two-dimensional systems. As T is reduced, conductivity drops rapidly into a power-law behaviour, and low-field magnetoconductance changes sign. This the authors argue is the result of a transition to one-dimensional conduction, and they show that the transition from 2D to 1D occurs at higher temperatures when the channel width is reduced to approximately 0.1 mu m. Conductivity corrections in 1D are found to be very large, so that a complete separation of interaction and localisation contributions is not possible. The current perturbation theories of interaction and localisation are therefore inadequate to explain these results.