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Diamond films have been obtained on Ta polycrystalline substrates from mixtures of methane and hydrogen by the hot-filament chemical vapor deposition technique. The structural characteristics of the polycrystalline deposits have been investigated by reflection high energy electron diffraction (RHEED), while the surface morphologies have been observed by scanning electron microscopy or carbon replica transmission electron microscopy. For one of the films, the formation of thermal spikes during the deposition process yielded a structure giving a RHEED pattern with d spacings and intensities not corresponding to the already identified carbon and diamond phases. On the base of the RHEED pattern the observed phase has been identified as a face-centered-cubic lattice, belonging to the space group F4̄3m and ascribed to a so-called X-diamond polytype.

Low-power pulsed-laser annealing ͑LPPLA͒ 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.

The experimental conditions necessary to obtain low-power pulsed-laser annealing (LPPLA) of implanted samples of GaAs are described. Simple theoretical estimates have been used to show that the sample's temperature evolution is such that it does not produce appreciable GaAs decomposition. Particular attention is paid to the spatial distribution of the energy over the laser beam cross section and the optical system used in the experiments. It is also pointed out that below the melting threshold, but above the upper limit of the energy window, within which the LPPLA is obtained, a structural disorder of the material is induced by the laser itself.