Self-assembled Ge wires with a height of only 3 unit cells and a length of up to 2 micrometers were grown on Si(001) by means of a catalyst-free method based on molecular beam epitaxy. The wires grow horizontally along either the [100] or the [010] direction. On atomically flat surfaces, they exhibit a highly uniform, triangular cross section. A simple thermodynamic model accounts for the existence of a preferential base width for longitudinal expansion, in quantitative agreement with the experimental findings. Despite the absence of intentional doping, first transistor-type devices made from single wires show low-resistive electrical contacts and single hole transport at sub-Kelvin temperatures. In view of their exceptionally small and self-defined cross section, these Ge wires hold promise for the realization of hole systems with exotic properties and provide a new development route for silicon-based nanoelectronics.
@article{arxiv.1208.0666,
title = {Monolithic growth of ultra-thin Ge nanowires on Si(001)},
author = {Jianjun Zhang and Georgios Katsaros and Francesco Montalenti and Daniele Scopece and Roman O. Rezaev and Christine Mickel and Bernd Rellinghaus and Leo Miglio and Silvano De Franceschi and Armando Rastelli and Oliver G. Schmidt},
journal= {arXiv preprint arXiv:1208.0666},
year = {2015}
}