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In this letter, we present an atomic-force-microscopy investigation of the Stranski-Krastanov growth of Ge on Si(100). Upon increasing the base width of the islands, two morphology transitions are found. The first transition occurs at a base width of similar to 50-60 nm and marks the: evolution from few-monolayer-thick terraces to square-base pyramidal islands. In the second transition, which takes place when the base width exceeds similar to 300 nm, the island shape changes from square base pyramids to tetragonal truncated pyramids. Both transitions are brought about by the need for the system to minimize the elastic energy.

The valence density of states of Ge grown epitaxially on Si(100) is investigated as a function of thickness by yield spectroscopy and photoemission techniques. A double edge is present in the yield data for thicknesses smaller than the lattice relaxation critical thickness. Furthermore, the line-up of the Ge states to the Si valence band varies with overlayer thickness. Photoemission techniques fail to detect this behavior. The causes for the discrepancy are analyzed.

Low-power pulsed-laser annealing (LPPLA) was applied to III-V compound semiconductors GaAs and InP. The effects have been analyzed using several experimental techniques such as reflection high-energy electron diffraction, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, and electrical measurements. In addition, a calculation method was developed to study the heat propagation in the irradiated sample during the LPPLA process. The irradiation conditions, realizing a uniform surface laser-energy distribution, made possible a unidimensional approach. The results obtained experimentally and by numerical modeling agree well if one assumes that a solid-phase epitaxy takes place. The XPS measurements for GaAs and InP show, in particular, that a range of the irradiation power density exists where the LPPLA can effectively restore the lattice order without appreciable alteration of the surface stoichiometry. At higher power density of irradiation, the As and P vacancies introduced by the laser, in GaAs and InP, respectively, may no longer be neglected. \textcopyright{} 1996 The American Physical Society.

The LUMO-derived band of the CsC60 compound was investigated by-means of x-ray and UV photoemission and photoelectric yield spectroscopies. A double-peak structure is found, with peak maxima at 1.1 eV and 0.35 eV. The relative magnitude of the two peaks is strongly temperature dependent: a large transfer of spectral weight from the lower- to the higher-binding-energy peak takes place upon cooling to 110 K. The peaks are tentatively attributed to the dimer and the polymeric phase respectively. However the behaviour as a function of temperature does not agree with the metastability of the dimer phase at room temperature. The position of the Fermi level is compatible with a correlated system on the border of the metal-insulating transition.

In this article we discuss the use of spectroscopic ellipsometry for an in situ and real time probe of three-dimensional self-organized Ge island growth on Si (100) surfaces. We will show that atomic force microscopy and x-ray photoemission spectroscopy can be combined with spectroscopic ellipsometry to give information on the size and shape evolution of the Ge islands as well as on the amount of Ge deposited on the Si surface.