Ultrasmall silicon quantum dots

We report the realization of extremely small single quantum dots in p-type silicon nanowires, defined by Schottky tunnel barriers with Ni and NiSi contacts. Despite their ultrasmall size the NiSi-Si-NiSi nanowire quantum dots readily allow spectroscopy of at least ten consecutive holes, and additionally they display a pronounced excited-state spectrum. The Si channel lengths are visible in scanning electron microscopy images and match the dimensions predicted by a model based on the Poisson equation. The smallest dots (< 12 nm) allow identification of the last charge and thus the creation of a single-charge quantum dot. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3155854]