Periodic arrays of epitaxial self-assembled SiGe quantum dot molecules grown on patterned Si substrates

Ex situ focused ion-beam (FIB) patterning of arrays of holes on Si (001) substrates results in the subsequent formation of SiGe quantum dot molecules at each of the patterned sites during heteroepitaxial growth under kinetically limited growth conditions where island formation is constrained. These quantum dot molecules are fourfold self-assembled island nanostructures bound by a central pit. During growth, material is ejected from the patterned sites forming the pits that in turn provide favorable sites for the cooperative nucleation of {105} faceted islands. The degree of order and quality of the resulting structures depend on many factors including growth temperature, ion-beam milling depth, Si buffer thickness, and spacings between FIB exposed sites. This technique provides a method for controlling the lateral placement of semiconductor nanostructures, which could be used in applications such as complex nanoelectronic architectures.