Effects of pulsed laser radiation on epitaxial self-assembled Ge quantum dots grown on Sisubstrates

Abstract

Laser irradiation of Ge quantum dots (QDs) grown on Si(100) substrates by solid-sourcemolecular beam epitaxy has been performed using a Nd:YAG laser (532 nm wavelength, 5 nspulse duration) in a vacuum. The evolution of the Ge QD morphology, strain andcomposition with the number of laser pulses incident on the same part of the surface, havebeen studied using atomic force microscopy, scanning electron microscopy and Ramanspectroscopy. The observed changes in the topographical and structural properties of theQDs are discussed in terms of Ge–Si diffusion processes. Numerical simulations have beendeveloped for the investigation of the temperature evolution of the QDs duringlaser irradiation. The obtained results indicate that the thermal behaviour andstructural variation of the nanostructures differ from conventional thermal annealingtreatments and can be controlled by the laser parameters. Moreover, an unusualisland motion has been observed under the action of subsequent laser pulses.