The electrical properties of nanoscale parallel semiconductor interfaces

Abstract

Nanosphere lithography has been used to prepare a series of ordered, periodic arrays of low barrier height n-Si/Ni nanometer-scale contacts interspersed amongst high barrier height n-Si/liquid contacts. To form the arrays, crystalline bilayers of close-packed latex spheres were deposited onto (100)-oriented n-type single crystal Si surfaces. The spheres formed a physical mask through which Ni was evaporated to produce regularly spaced and regularly sized Si/Ni contacts. By varying the diameter of the latex spheres from 174 nm to 1530 nm, geometrically self-similar Si/Ni structures were produced having triangular Si/Ni regions with edge dimensions of 100 - 800 nm. The resulting Si surfaces were used as electrodes in contact with a methanolic solution of LiClO4 and 1,1'-dimethylferrocene/1,1'-dimethylferrocenium. The current-voltage and photoresponse properties of these mixed barrier height contacts were strongly dependent on the size of the Ni regions, even though the fraction of the Si surface covered by Ni remained constant. Electrodes formed from large-dimension Si/Ni and Si/electrolyte contacts behaved as expected for two area-weighted Schottky diodes operating independently and in parallel, whereas electrodes having nanoscale Si/Ni and Si/liquid contacts behaved in quantitative accord with effective barrier height theories that predict a pinch-off effect for mixed barrier height systems of sufficiently small physical dimensions.