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ABSTRACT: High Q factor ring resonators based on Si clusters sandwich slot-waveguide structure have been fabricated by standard DUV lithography. These devices are considered an important step towards the demonstration of an all optical logic gate.
Group IV Photonics, 2008 5th IEEE International Conference on; 10/2008
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ABSTRACT: Precipitation and crystallization of Si nanocrystals have been monitored by means of Raman spectroscopy. SiO <sub>x</sub> films with different compositions have been deposited by low-pressure chemical-vapor deposition technique onto silica substrates and treated to temperatures exceeding 800 ° C . The evolution of the Raman signal with the thermal budget reveals that the silicon transition from amorphous to crystalline state shifts to higher temperatures as the Si content in the layers is lowered. A rather complete crystallization of the nanoparticles is achieved after annealing at 1250 ° C for a Si excess lower than 20%, while for higher excesses the crystalline fraction reaches only 40%, suggesting the formation of a crystalline core surrounded by an amorphous shell. The Raman spectra have been analyzed by a phonon confinement model that takes into account stress effects. An increasing nanocrystal size, from 2.5 to 3.4 nm, has been estimated when the Si excess varies from 16 to 29 at . % . For small Si nanocrystals a strong hydrostatic stress has been observed, induced by a very abrupt transition with the surrounding SiO <sub>2</sub> . Its magnitude correlates with the increase in thermal budget required for the crystallization of the amorphous clusters. This study underlines the fundamental role of hydrostatic stress in retarding the crystallization of Si nanoclusters.
Journal of Applied Physics 09/2008; · 2.17 Impact Factor
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F. Mini,
G.L. Scialino,
M. Milano,
V. Lubrano,
P. Conforto, P. Pellegrino,
D. Caswell,
J. Santiago Prowald,
K. Van't Klooster,
A. Cherniavsky,
V. Korneev,
I. Vorobey,
A. Fedoseev
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ABSTRACT: This paper presents the development and the ultimate results of the qualification activities of the 12m unfurlable Reflector Assembly of the Large Deployable Antenna (LDA), jointly developed by the Prime Contractor: Alcatel Alenia Space Italia and several Partners, under an ESA contract. The qualification campaign will be finalized within September 2006, opening near term opportunities for space applications relying on a European technology.
Antennas and Propagation, 2006. EuCAP 2006. First European Conference on; 12/2006
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ABSTRACT: Frequency of mucosal damage to the esophagus, stomach, and duodenum was investigated in 176 children with coeliac disease (CD) during 230 upper GI endoscopies performed to obtain duodenal biopsy specimens and was compared with findings in 230 age-matched children who underwent endoscopy for upper GI complaints without CD (non-CD patients). To evaluate a possible association with gluten ingestion, we then compared frequency of mucosal damage in patients on a gluten-containing diet and those on a gluten-free Diet (GFD). In children with CD, frequency of esophageal damage seen at endoscopy and of peptic esophagitis shown by histology were significantly lower than in non-CD patients (p < 0.01) due to the very low frequency of mucosal damage in CD children on GFD; however, frequency of columnar metaplasia was significantly higher (p < 0.05). At endoscopy, CD children had a significantly lower frequency of gastric abnormalities, but histology showed a higher prevalence of superficial chronic gastritis (SCG; p < 0.01). SCG was associated with gluten ingestion, since its frequency in CD children on GFD was similar to the frequency in non-CD patients. At endoscopy, frequency of duodenal mucosal damage was similar in CD and non-CD patients. In addition to villous atrophy, histology showed a significantly higher frequency of duodenitis in CD children on a gluten-containing diet (p < 0.001 vs. non-CD patients; p < 0.05 vs. CD children on GFD). Our findings show that the mucosa of the whole upper GI tract can be damaged in CD patients and that the prevalence of some changes is higher with a gluten-containing diet.
Journal of Pediatric Gastroenterology and Nutrition 02/1993; 16(2):172-7. · 2.30 Impact Factor
