Effect of submonolayer carbon on nanoscale Ge dot growth on Si(0 0 1) substrates

The effect of a small amount of C atoms on the Ge dot morphology on Si(0 0 1) has been investigated. Submonolayers of carbon were deposited on Ge wetting layers to modify the subsequent Ge dot growth mode. AFM studies revealed that the C layer has two main effects on the Ge dot growth, which were to promote a structural transition from huts to domes and to initiate three-dimensional growth even on a thin wetting layer. The results indicated that the C atoms, which were localized at the interface between the Ge wetting layer and the Ge dot, induced a strain field and destabilized the hut structure. As a result, Ge domes could be grown with the help of the C atoms at relatively low temperature, suggesting a possibility to produce small quantum dots with high number density as well as size uniformity.