STM study of pulsed laser assisted growth of Ge quantum dot on Si(1 0 0)-(2 × 1)

Abstract

Ge quantum dot formation on Si(1 0 0)-(2 × 1) by nanosecond pulsed laser deposition under laser excitation was investigated. Scanning tunneling microscopy was used to probe the growth mode and morphology. Excitation was performed during deposition using laser energy density of 25-100 mJ/cm 2. Faceted islands were achieved at a substrate temperature of ∼250 • C only when using laser excitation. The island morphology changes with increased laser excitation energy density although the faceting of the individual islands remains the same. The size of the major length of islands increases with the excitation laser energy density. A purely electronic mechanism of enhanced surface diffusion of the Ge adatoms is proposed. 2 Experiment Germanium quantum dots were grown in an ultrahigh vacuum (UHV) chamber (∼ 7×10 −11 Torr) by PLD equipped with STM. The Ge target was rotated at 6 rpm to minimize particle formation during deposition. The laser beam profile on target and target rotation speed were set such