1,721,005 research outputs found
Scanning electron microscopy of thinned specimens: From multilayers to biological samples
No full textThe rules governing image formation of thin specimens in scanning and scanning transmission electron microscopy at low energy, deduced from the observation of semiconductor multilayers, were validated on specimens defined by a much more complex structure as the biological ones. It is shown that for a suitable specimen thickness it is possible to have, at the same time, backscattered electron images and scanning transmission electron images with a comparable resolution. Moreover, the nonconductive biological samples can be observed without charging effects if they are thin enough to ensure that a significant fraction of the electron beam crosses the specimen
Effects of beam-specimen interaction on the observation of reverse-biased junction
No full textElectron interferometry experiments on straight reverse-biased p-n junctions have been carried out in a transmission electron microscope. The trend of the interference fringes as well as the shape of the interference region are able to give direct information about the phase variation across the junction. Agreement between theory and experiment is obtained by introducing a suitable surface density charge produced by the beam at the interface between the silicon and the native oxide. Also the depletion layer width and the overall electric field topography are strongly modified by the charged layers. The results confirm the main predictions of the improved model in a more reliable way than those obtained through previous out-of-focus observations and point out the active role of the electron beam in the electric characterization of semiconductor devices
Electron microscope calibration for the Lorentz mode
No full textThe calibration of a modern electron microscope for Lorentz microscopy observations has been performed using diffractogram, Fresnel diffraction fringe analysis and low-angle electron diffraction methods. An example related to the observations of electrostatic fields associated to a thinned reverse-biased p–n junction is also reported
Transmission electron microscopy and optical characterization of nano-particles
No full textSome of the capabilities of Transmission Electron Microscopy (TEM) in the field of the structural characterization of metal clusters, with dimensions in the nanometer range, are here presented. Three main area of interest are concerned, i.e., measurements of the variation in the lattice parameter as a function of the size decrease by means of electron diffraction; darkfield investigations on the reduction of the melting point; high-resolution study of the dynamic behaviour (instabilities) of the clusters. Optical reflectivity measurements are shown to give useful additional information on the systems here investigated: in particular, the presence of a super-cooling effect and of a hysteresis cycle on going from heating to cooling is evidenced
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Composition and structure of Si-Ge layers produced by ion implantation and laser melting
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