A low-cost purification technique was evaluated on multicrystalline silicon (mc-Si). It consists of an efficient impurity trapping process involving nanocavities created by plasma immersion ion implantation (PIII). The study consisted of assessing (i) the creation of nanocavities by PIII and (ii) their ability to trap impurities in real conditions (without intentional contamination). Square pieces of p-type me-Si samples, having a surface of 4 cm(2) were used. They were implanted with hydrogen by PIII at 20 kV with a fluence of 5 x 10(16) cm(-2) and then annealed for 30 min, in the temperature range 673-1273 K. The evolution of shape, size and spatial distribution of nanocavities was studied by transmission electron microscopy and time of flight secondary ion mass spectrometry in order to check both the formation of cavities and to test their ability to getter impurities by either precipitation or chemisorption. Results reveal surprisingly that, despite the triangular as-implanted H profile, nanocavities can be created by evidently because of the multi-energetic and high flux implantation (about 8 x 10(13) cm(-2) s(-1), 40-80 times greater than in conventional implantation) and that they are able to trap various impurities, initially present in me-Si, such as Fe, Cu and Ni (according to their Gibbs energy), competing with the many existing gettering sites available in me-Si, such as Si-related precipitates (oxygen, carbon, nitrogen or metal silicides), dislocations and grain boundaries. The area containing the biggest cavities have the highest density of gettering sites, especially for Cu, which can be trapped either by chemisorption (since it has higher binding energy with cavities) or by Cu3Si precipitation since the corresponding volume expansion can be damped by surrounding cavities. (C) 2015 Elsevier B.V. All rights reserved.

BACKGROUND:The aim of this study was to prospectively compare the diagnostic accuracy of videoendoscopy, with and without Lugol staining, for the detection of esophageal cancer in alcoholic or smoking patients older than 40 years.METHODS:Daily alcohol and tobacco consumption and overt and latent symptoms were noted. The 158 patients included were examined by videoendoscopy and with Lugol dye.RESULTS:The mean consumption of alcohol and tobacco was 86 +/- 49 gm/day for 26 +/- 11 years, and 30 +/- 18 pack-years, respectively. Twenty-five patients had no symptoms. Before Lugol staining, 12 patients had endoscopically identified cancerous lesions. After Lugol staining, 13 patients had 17 esophageal cancers, 3 of which were high-grade dysplasia. The prevalence of esophageal cancer was 8.2%: 95% CI [4,14]. Dye-free surfaces were significantly larger than the endoscopic patterns observed before Lugol staining (11.6 +/- 9.2 cm2 vs 1.4 +/- 1.7 cm2; p < 0.02).CONCLUSIONS:In an alcoholic smoking population, the prevalence of esophageal cancer detected by endoscopy is high and not related to symptoms described by patients. Lugol staining only moderately improves the diagnostic accuracy of videoendoscopy; its main advantage is the assessment of the mucosal extension of esophageal cancer.