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Self-assembled germanium quantum dots ͑QDs͒ were grown on Si͑100͒-͑2 ϫ 1͒ by pulsed laser deposition. In situ reflection-high energy electron diffraction ͑RHEED͒ and postdeposition atomic force microscopy are used to study the growth of the QDs. Several films of different thicknesses were grown at a substrate temperature of 400°C using a Q-switched Nd:yttrium aluminum garnet laser ͑ = 1064 nm, 40 ns pulse width, 23 J / cm 2 fluence, and 10 Hz repetition rate͒. At low film thicknesses, hut clusters that are faceted by different planes, depending on their height, are observed after the completion of the wetting layer. With increasing film thickness, the size of the clusters grows and they gradually lose their facetation and become more rounded. With further thickness increase, the shape of these clusters becomes domelike with some pyramids observed among the majority of domes. The effect of the laser fluence on the morphology of the grown clusters was studied. The cluster density was found to increase dramatically while the average cluster size decreased with the increase in the laser fluence. For a laser fluence of 70 J / cm 2 , dome-shaped clusters that are smaller than the large huts formed at 23 J / cm 2 were observed. At a substrate temperature of 150°C, misoriented three-dimensional ͑3D͒ clusters are formed producing only a RHEED background. At 400 and 500°C, huts and a lower density of domes are formed, respectively. Above 600°C, 3D clusters are formed on top of a discontinuous textured layer.

Self-assembled Ge quantum dots are grown on Si(100)-2×1 by pulsed laser deposition. The growth is studied by in situ reflection high-energy electron diffraction and postdeposition atomic force microscopy. After the completion of the wetting layer, transient hut clusters, faceted by different planes, are observed. When the height of these clusters exceeded a certain value, the facets developed into {305} planes. Some of these huts become {305}-faceted pyramids as the film mean thickness was increased. With further thickness increase, dome clusters developed on the expense of these pyramids.

The effects of laser-induced electronic excitations on the self-assembly of Ge quantum dots on Si͑100͒-͑2 ϫ 1͒ grown by pulsed laser deposition are studied. Electronic excitations due to laser irradiation of the Si substrate and the Ge film during growth are shown to decrease the roughness of films grown at a substrate temperature of ϳ120°C. At this temperature, the grown films are nonepitaxial. Electronic excitation results in the formation of an epitaxial wetting layer and crystalline Ge quantum dots at ϳ260°C, a temperature at which no crystalline quantum dots form without excitation under the same deposition conditions.

Step-flow growth mode is observed for 100 fs pulsed laser deposition (fsPLD) of Si on vicinal Si(100)-2×1, while the Volmer–Weber mode is observed for fsPLD of Si on Si(100)-1×1. Reflection high-energy electron diffraction (RHEED) is used to in situ monitor the dynamics of the film growth while ex situ atomic force microscopy (AFM) is used to observe the morphology of the grown film. For Si on Si(100)-2×1, the diffraction pattern’s basic features remain unchanged during deposition, indicating step-flow growth. AFM shows smooth growth on flat terraces. However, for Si on Si(100)-1×1 two growth behaviors are observed. For a laser fluence of 1.9 J/cm2 and a substrate temperature below ∼400 °C, we observe a decay of the RHEED peaks until they completely disappear, indicating the loss of the long-range order in the grown film. Postdeposition analysis shows three-dimensional (3D) clusters associated with the Volmer–Weber growth mode. On the other hand, deposition above ∼400 °C at the same laser fluence results in the decay and eventual disappearance of the reflection diffraction peaks accompanied by the evolution of a transmission pattern instead. Transmission patterns appear when the electrons are diffracted in a transmission mode through 3D crystallites. These crystallites are observed in the AFM images.