RESUMO
The DPP (diethyl 1-propylphosphonate) and ODPA (octadecylphosphonic acid) molecules are studied as precursors for the monolayer doping (MLD) of germanium. Their adsorption behaviour is investigated, revealing different physicochemical interactions between the phosphorus-containing molecules and the Ge surfaces. It is discovered that DPP adsorption occurs after the oxidation of Ge surface, while the ODPA undergoes chemisorption on -H terminated surfaces. Quantitative phosphorus analysis demonstrates that in the first case more than one monolayer is formed (from 2 to 4), while in the second a single monolayer is formed. Moreover, the analysis of phosphorus diffusion from the surface layers into the Ge matrix reveals that conventional thermal annealing processes are not suitable for Ge injection due to a higher activation energy of the process in comparison with silicon. On the contrary, pulsed laser melting is effective in forming a doped layer, owing to the precursor's decomposition under UV light.
RESUMO
A bent lithium niobate strip was exposed to a 400-GeV/c proton beam at the external lines of CERN Super Proton Synchrotron to probe its capabilities versus coherent interactions of the particles with the crystal such as channeling and volume reflection. Lithium niobate (LiNbO3) exhibits an interplanar electric field comparable to that of Silicon (Si) and remarkable piezoelectric properties, which could be exploited for the realization of piezo-actuated devices for the control of high-energy particle beams. In contrast to Si and germanium (Ge), LiNbO3 shows an intriguing effect; in spite of a low channeling efficiency (3%), the volume reflection maintains a high deflection efficiency (83%). Such discrepancy was ascribed to the high concentration (10(4) per cm2) of dislocations in our sample, which was obtained from a commercial wafer. Indeed, it has been theoretically shown that a channeling efficiency comparable with that of Si or Ge would be attained with a crystal at low defect concentration (less than ten per cm2). To better understand the role of dislocations on volume reflection, we have worked out computer simulation via dynecharm++ Monte Carlo code to study the effect of dislocations on volume reflection. The results of the simulations agree with experimental records, demonstrating that volume reflection is more robust than channeling in the presence of dislocations.
RESUMO
We demonstrate that substitutional B in silicon can migrate even at room temperature and below, stimulated by a high interstitial flux. Once mobile B is formed, it migrates for long distances with a diffusivity >5 x 10(-13) cm(2)/s, until it assumes an immobile configuration with a migration length independent of the temperature. This phenomenon is present during secondary ion mass spectrometry (SIMS) analyses of B profiles, altering the profile during the analysis itself. These results shed new light on all the data based on SIMS analyses and reported in literature in the last decades.
RESUMO
This study analyzed the influence of lactation on aggression by group-living Japanese macaque females. Data collected during 268 hr of observation showed that lactating females exhibited much more aggression than did females in any other reproductive condition under investigation. This postpartum aggression showed distinctive features in terms of time course during lactation and target selectivity but it was not characterized by a higher intensity and severity. Aggression increased progressively during the first 6 weeks of lactation, reached its highest levels between 7th and 9th weeks postpartum, and thereafter diminished. The relative percentages of threat, chase, and physical attack did not change with the reproductive condition. Lactating females were selective in their choice of targets, with young females being the recipients of nearly 90% of the total of their aggression.
