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Semiconducting iron suicide dots with dimensions ranging between 5 and 100 nm can be obtained by ion implantation on Si wafers and exhibit interesting photo- and electro- luminescent properties. In our study we use structural and optical characterization as well as theoretical modelling in order to: i) discriminate among intrinsic effects of FeSi2 dots and effects due to lattice damage and Si matrix; ii) identify the range of physical parameters (size, phase, electronic structure) corresponding to the luminescent dots.

Electromigration is one of the main failure mechanisms limiting the miniaturization of microelectronic devices. As a consequence of the high current densities in the interconnections, hillocks and voids are formed and their evolution can modify the electrical performances of devices till failure. To characterize electromigration damages, today's failure analysis techniques require removal of the protection passivation to allow scanning electron microscope or focused ion beam microscope imaging, but the removal process itself can damage the surface of the metal stripes. Due to the optical transparency of the passivation, near-field scanning optical microscopy can be used to overcome this problem. We succeeded in obtaining the first near-field images in resolution < 150 nm of electromigrationdamaged metal structures without complete removal of the passivation. The latter was thinned to 100-200 nm to allow the evanescent waves to reach the metal structures and illuminate a subwavelength zone of the sample. Near-field images show the presence of hillocks and voids of dimensions down to 250 nm which can be due only to electromigration, and, in this sense, they are more reliable than the usual scanning electron microscope images.

Standard rate equation models of island formation in the InAs/GaAs(001) system have been reassessed in terms of new experimental evidence from real time in-situ reflectance anisotropy spectroscopy (RAS) measurements. These measurements have revealed the behaviour and role of the wetting layer in the modified Stranski-Krastanov growth mode during molecular beam epitaxial growth showing that it can continue to significantly increase in thickness following the onset of islanding. The presence of two dimensional (2D) islands, which act as precursors to three dimensional (3D) islands (the quantum dots) in conventional models, does in principle allow an extension of the "wetting layer". However, it has been found necessary to extend the standard model to include extra terms that allow material to be incorporated into (and detach from) the wetting layer and which cannot convert to 3D islands. With this improved model, it is found possible to achieve agreement with the RAS measurements.