Fabrication of discrete gallium nanoislands on the surface of a Si(001) substrate using a focused ion beam

A gallium focused ion beam (FIB) has been used to implant Ga at specific sites on the surface of undoped Si(001) substrates. Upon annealing at 600°C, discrete nanoscale surface islands form within the FIB patterned regions when the total Ga ion dose, or fluence, is greater than 1.0 × 10 ¹⁶ionscm^{- 2}. The number of islands depends on the size of the irradiated region and a single island can be achieved for a FIB milled region that is 100nm × 100nm. The average sizes of the islands were found to range from 24.5nm when exposed to a total ion dose of 1.2 × 10 ¹⁶ionscm^{- 2} to 45nm for a dose of 3.0 × 10 ¹⁶ionscm^{- 2}. We have confirmed that these surface islands are metallic Ga by performing a selective chemical etch that removes the islands and by transmission electron microscopy characterization. These patterned Ga surface templates could serve as nucleation sites for the lateral arrangement of discrete quantum dot structures.