Electrical transport in three-dimensional ensembles of silicon quantum dots

Following our previous works in which we tried to understand the transport mechanisms below and at the conductivity percolation threshold of three-dimensional ensembles of Si quantum dots (QD's), in the present work we try to derive a comprehensive understanding of the transport mechanisms above the percolation threshold. Our conclusions are based on a systematic study of the electrical properties of Si nanocrystallite ensembles that are embedded in an insulating matrix as a function of their density. To evaluate the transport mechanisms we introduce the concept of ``touching,'' showing that its application enables to suggest that the percolation transition is associated with the onset of extended states-like transport in a continuous disordered network. This understanding provides a framework for the discussion of the transport in ensembles of QD's in general and in ensembles of Si QD's in particular.