Masmec (Italy)

In Image Guided Surgery, an electromagnetic tracking system is used to locate surgical instruments in the patient's anatomical 3D model. In this work we illustrate the development and the evaluation of a new Electromagnetic Tracking system (EMTS) able to provide a large tracking volume. The innovation of this EMTS consists in the development of the Field Generator (FG), which includes five properly designed coils. Attention has been paid to the magnetic field generated by each coil in order to comply with the safety limits imposed by IEEE Std C95.1 and C95.6. The simultaneous transmission of the five coils is possible thanks to frequency division multiplexing. To validate the proposed design, a detailed noise analysis was performed to identify the main contributions to measurement error. Several experimental tests were carried out in different working conditions to identify a suitable model of measurement error and identify main error contributions.

Unexpected excess current was obtained in GaAs/InAs quantum dot structures at low temperatures and low current levels. This excess current exhibited instabilities with changing the bias, and over the time. It has been concluded that the excess current is a minority injection current connected with the high recombination rate through quantum dots. The instabilities are connected with unstable charge occupation of quantum dots.

TiO2 and W/TiO2 thin films have been prepared by a chemically modified sol-gel technique. Oxide-polymer thin films were deposited by dip-coating. Annealing at 500°C results in nanosized structurally stable oxides films. The dopant concentration led to a final W/Ti ratio of 1/33, 5/33, 10/33. The morphological and structural characteristics of thin films were studied through microraman, GIXRD, SEM and TEM. A microstructural comparison between pure and doped TiO2 layers is reported. Ethanol and methanol sensing properties are tested. TiO2 and W/TiO2 structural features and sensing characteristics are compared.

Highly mismatched GaAs epitaxial layers with thickness ranging from 15 nm to 7 μm have been grown on InP substrates by atomospheric pressure metalorganic vapor phase epitaxy. Layers thinner than 30 nm exhibited 3-D growth mechanism; in the thicker layers, the islands coalesced and then the growth followed the layer by layer mechanism. The elastic strain and the extended defects have been studied by high resolution x-ray diffraction and transmission electron microscopy, respectively. The common observation of planar defects, misfit, and threading dislocations in the layers has been confirmed. The results on the elastic strain release have been discussed on the basis of the equilibrium theory.

Abstract Some examples of the possibilities that panchromatic cathodoluminescence (PCL) offers in the scanning electron microscopy (SEM) characterization of III‐V semiconductors are presented. Investigations on lattice‐mismatched InGaAs/InP, InGaAs/ GaAs single heterostructures, and InGaAs/GaAs superlattices and GaAs/Ge and GaAs/InP single layers are shown. Further, the use of PCL as a support in the nondestructive determination of the sensitivity limit of Rutherford backscattering and x‐ray diffraction techniques in the study of strain release in some of the above mentioned heterostructures is presented. Finally, PCL on‐line study of dislocation movement induced by electron beam irradiation in the SEM, as evidence of InGaAs/GaAs superlattice metastability, is also presented.

High-resolution neutron powder diffraction studies were performed on several compounds of the type YFe12-xAlx (x=8, 7, 6). The authors observed a strong preferential site occupation of Fe on one of the three non-equivalent transition metal sites of the hMn12-type structure. In particular the 8f site is found to be markedly populated by Fe atoms, while there is a strong preference of Al for the 8i site.

Adsorption processes were investigated for the first time on a IV–VI substrate, PbTe, by photoemission spectroscopy with synchrotron radiation Ge, Al, and In overlayers on cleaved PbTe(100) all create an inversion layer at the PbTe side of the interface. Substantial Pb and Te outdiffusion is observed even at room temperature, resulting in nonabrupt interfaces. The band discontinuities of the PbTe–Ge interface are much different from those theoretically predicted by the electron affinity rule.