thin film epitaxy

Strain induced self-assembly provides an attractive route to nanofabrication of semiconductor quantum dots on surfaces. Recent experiments have demonstrated that combining the strain induced self-assembly with surface patterning provides an effective method to further improve the size uniformity and spatial ordering of quantum dots. However, the underlying mechanisms responsible for such improvement remain poorly understood. Recently, we have developped theoretical models to elucidate the strain induced growth instability and island nucleation on patterned substrates.

When a strained film is grown on a vicinal substrate, the steps advance like a train when the deposited atoms have sufficient mobility to reach the step edges. However, as the steps advance, the strain-induced force monopoles associated with the steps cause the steps to attract to each other (J. Tersoff, PRL 74, 4962, (1995)), resulting in a thermodynamic instability of the steps in the form of step bunching (J. Tersoff, et al., PRL 75, 2730 (1995)).