Depth measurements of etch-pits in GaN with shape reconstruction from SEM images
ABSTRACT The method, which allows shape reconstruction by reading the intensity from the scanning electron microscopy image, is presented and discussed in details. The method is applied to read the morphology of etch-pits, which were formed on the GaN surface by etching in molten KOH-NaOH eutectic mixture to delineate dislocations. The etch-pit depth distributions are obtained and used to determine densities of pits related to screw, mixed or edge-type dislocations. The results are compared with atomic force microscopy.
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ABSTRACT: The methodology for fracture analysis of polymeric composites with scanning electron microscopes (SEM) is still under discussion. Many authors prefer to use sputter coating with a conductive material instead of applying low-voltage (LV) or variable-pressure (VP) methods, which preserves the original surfaces. The present work examines the effects of sputter coating with 25 nm of gold on the topography of carbon-epoxy composites fracture surfaces, using an atomic force microscope. Also, the influence of SEM imaging parameters on fractal measurements is evaluated for the VP-SEM and LV-SEM methods. It was observed that topographic measurements were not significantly affected by the gold coating at tested scale. Moreover, changes on SEM setup leads to nonlinear outcome on texture parameters, such as fractal dimension and entropy values. For VP-SEM or LV-SEM, fractal dimension and entropy values did not present any evident relation with image quality parameters, but the resolution must be optimized with imaging setup, accompanied by charge neutralization. SCANNING 00: 1-9, 2012. © 2012 Wiley Periodicals, Inc.Scanning 05/2013; 35(3). DOI:10.1002/sca.21048 · 1.44 Impact Factor
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ABSTRACT: Pitting corrosion is a damage mechanism quite serious and dangerous in both carbon steel boiler tubes for power plants which are vital to most industries and stainless steels for orthopedic human implants whose demand, due to the increase of life expectation and rate of traffic accidents, has sharply increased. Reliable methods to characterize this kind of damage are becoming increasingly necessary, when trying to evaluate the advance of damage and to establish the best procedures for component inspection in order to determine remaining lives and failure mitigation. A study about the uncertainties on the topographies of corrosion pits from 3D SEM images, obtained at low magnifications (where errors are greater) and different stage tilt angles were carried out using an in-house software previously developed. Additionally, measurements of pit depths on biomaterial surfaces, subjected to two different surface treatments on stainless steels, were carried out. The different depth distributions observed were in agreement with electrochemical measurements.Micron 10/2011; 43(2-3):387-95. DOI:10.1016/j.micron.2011.10.005 · 2.06 Impact Factor
Conference Paper: Analisys of positron focusing section for SPring-8 linac[Show abstract] [Hide abstract]
ABSTRACT: In the SPring-8 positron beams will be used and generated in the linac. In this paper, simulations and experiments of a test apparatus for the convertor are described. Results of simulations are qualitatively coincident with that of experiments, and from simulation results, an electron/positron conversion efficiency of 0.5% is obtained at the end of the convertor, with a feasible design of the convertor system. A future plan of superconducting magnet system for the convertor is also mentionedParticle Accelerator Conference, 1995., Proceedings of the 1995; 06/1995