Catalyst Stimulates Self-Doping In Silicon Nanowires

Doping semiconductors such as silicon with select impurity atoms is a common method for customizing the material’s electronic properties for various applications. Yet atomic-level control and understanding of doping processes remain elusive. Some of those details have now been revealed by a study that pinpointed the three-dimensional position and elemental identity of the atoms in doped silicon nanowires (Nature, DOI: 10.1038/nature11999). Such nanowires are already used or are being developed for use in nanoelectronics, biosensing, and other applications. Oussama Moutanabbir of École Polytechnique of Montreal, Dieter Isheim and David N. Seidman of Northwestern University, and coworkers grew silicon nanowires via an aluminum-catalyzed vapor deposition method and generated atom-specific tomographs of the wires. The team found that aluminum triggers a self-doping process, resulting in an unexpectedly high concentration of aluminum atoms evenly distributed throughout the wires. Aluminum doping during nanowire growth enhances silicon’s charge conductivity. This self-doping process sidesteps the need for postgrowth doping, which is required for the more common gold-catalyzed silicon nanowires. The team proposes that these findings, which they rationalize on the basis of a solute-trapping model they developed, may lead to nanowires with tailored shapes and chemical compositions.