Electron spin and cyclotron resonance of laser annealed silicon

EPR and cyclotron resonance investigations have been performed on laser annealed Si wafers, leading to the identification of the [V + O i]- complex in virgin Si and to a donor signal quenching in P-implanted Si

Geometrical factor in multi-interface homostructures

In an experimental investigation carried out on multilayer silicon homostructures (of the n+-n-n+ type) an electric interaction between the two homointerfaces through majority carriers as a function of the geometrical factor has been shown. The two model homointerfaces were formed in the same monocrystal (CVD epitaxy) by only an abrupt change in the impurity doping level. Samples differing in the spacing of their parallel interfaces were characterized in the stationary and steady states (static and quasi-static regimes) to reveal modifications in their macroscopic transport. It has been demonstrated that the thermionic emission current, normally taken into account in the barrier transport (with large potential barriers) dominates in only two of five characteristic bias intervals. The two other phenomena, also related to the geometrical factor, i.e. the diffusion-drift and tunneling currents, dominate the conduction over practically the whole dc-bias range. These results allow the study of short and long range electrical interactions as well as the free carrier micromovement of simple and complex semiconductor interfaces of multilayer devices

Recrystallization of silicon by pulsed lasers

Calculation of the evolution of temperature during pulsed laser annealing has been performed. The results are presented in directly useful figures for the two kinds of laser generally used (YAG, Ruby). The results are compared to various experimental measurements performed by RBS. If the crystallographic quality is quite good, TSC and DLTS measurements have shown that electrically active defects are still present after laser annealing

ELECTRON SPIN RESONANCE INVESTIGATION OF THE EFFECTS OF THE H2+ IMPLANTATION AND DIFFUSION ONE THE LASER INDUCED DEFECTS IN VIRGIN SILICON

Electron paramagnetic resonance of the defects induced by laser annealing at high power density (2 J/cm-2) has been investigated in virgin FZ semi-insulating Silicon. A further H2+ implantation and diffusion is inactive on the signal observed at gx = 2.0055 ± 0.0005. This is consistent with the attribution of X to the dangling bonds, created by the mechanical stresses during the thermal shock, as they are not passivated by molecular hydrogen

SEM CHARACTERIZATION OF EFG POLYCRYSTALLINE SILICON SOLAR CELLS REALIZED BY ION IMPLANTATION AND LASER ANNEALING WITH OVERLAPPING PULSES

Atomic and molecular ion implantation (AMI) of non mass separated PF5 ions has been used to form the N+ layer on EFG ribbon. A pulsed Nd-YAG laser operating at a high repetition rate (10 kHz) was then employed to anneal the amorphized layer via liquid phase epitaxy. The properties of the recrystallized layers have been analyzed by SEM with secondary electron micrography and EBIC. The following results have been observed. At low electron beam energies (below 12 keV), strong EBIC recombination currents resulting from the overlapping laser pulses is clearly visible. At higher energies (above 20 keV), the recombination due to the grain boundaries in the ribbon becomes dominant. The regrowth after annealing replicates exactly the underlying structure. Finally, some electrical characteristics of the doped layers (doping profile) as well as the photovoltaïc performance are presented. Efficiencies up to 11 % have been obtained under AMI conditions

Alexandrov spaces with integral current structure

We endow each closed, orientable Alexandrov space $(X, d)$ with an integral current $T$ of weight equal to 1, $\partial T = 0 and \set(T) = X$, in other words, we prove that $(X, d, T)$ is an integral current space with no boundary. Combining this result with a result of Li and Perales, we show that non-collapsing sequences of these spaces with uniform lower curvature and diameter bounds admit subsequences whose Gromov-Hausdorff and intrinsic flat limits agree

Light-chain-induced renal tubular acidosis: effect of sodium bicarbonate on sodium-proton exchange

We measured sodium-proton (Na+/H+) exchange in lymphocytes and platelets of a 46-year-old woman with the adult Fanconi syndrome before, during, and after treatment with NaHCO3. Kappa light chains in her urine and unique but rarely observed crystalline structures confirmed the presence of light-chain nephropathy. Her glomerular filtration rate was only moderately impaired at 72 ml/min. NaHCO3 at 1, 3, and 5 mmol/kg/day for 5 days increased her serum HCO3 and pH from 17 to 21 mmol/l and 7.28 to 7.39 respectively. Plasma renin and aldosterone values were decreased by NaHCO3. Na+/H+ exchange (δHi/min) was measured with the fluorescent marker BCECF after acidification of lymphocytes and platelets with sodium propionate at five (10-50mM) doses. Na+/H+ exchange was accelerated in this patient compared to normal controls. NaHCO3 treatment significantly decreased Na+/H+ exchange in lymphocytes, but not in platelets. These findings suggest that Na+/H+ exchange can be influenced by NaHCO3 ingestion at doses that only modestly affect systemic pH. Since Na+/H+ exchange is involved in stimulus response coupling, cell growth regulation, cell differentiation, and perhaps the progression of nephrosclerosis, these observations may have clinical relevanc

PULSED AND CW LASER TREATMENTS OF IMPLANTED POLYSILICON SOLAR CELLS

Conventional ion implantation and unanalyzed ion bombardment have been used to elaborate the rectifying N+ contact of polycrystalline silicon (Wacker, HEM, CGE) solar cells. Two surface laser annealing in the liquid phase (Nd : YAG laser) and in the solid phase (CO2 laser) regimes have been used. The properties of the solar cells so processed have been investigated. For both doping procedures and both annealing techniques, the cells (conversion) efficiencies under AM1 illumination exceeded 11% for the various polysilicon substrates

Prevention of recurrent hip fracture

Our objective was to describe the interventions aimed at preventing a recurrent hip fracture, and other injurious falls, which were provided during hospitalization for a first hip fracture and during the two following years. A secondary objective was to study some potential determinants of these preventive interventions. The design of the study was an observational, two-year follow-up of patients hospitalized for a first hip fracture at the University Hospital of Lausanne, Switzerland. The participants were 163 patients (median age 82 years, 83% women) hospitalized in 1991 for a first hip fracture, among 263 consecutively admitted patients (84 did not meet inclusion criteria, e.g., age >50, no cancer, no high energy trauma, and 16 refused to participate). Preventive interventions included: medical investigations performed during the first hospitalization and aimed at revealing modifiable pathologies that raise the risk of injurious falls; use of medications acting on the risk of falls and fractures; preventive recommendations given by medical staff; suppression of environmental hazards; and use of home assistance services. The information was obtained from a baseline questionnaire, the medical record filled during the index hospitalization, and an interview conducted 2 years after the fracture. Potential predictors of the use of preventive interventions were: age; gender; destination after discharge from hospital; comorbidity; cognitive functioning; and activities of daily living. Bi- and multivariate associations between the preventive interventions and the potential predictors were measured. Inhospital investigations to rule out medical pathologies raising the risk of fracture were performed in only 20 patients (12%). Drugs raising the risk of falls were reduced in only 17 patients (16%). Preventive procedures not requiring active collaboration by the patient (e.g., modifications of the environment) were applied in 68 patients (42%), and home assistance was provided to 67 patients (85% of the patients living at home). Bivariate analyses indicated that prevention was less often provided to patients in poor general conditions, but no ascertainment of this association was found in multivariate analyses. In conclusion, this study indicates that, in the study setting, measures aimed at preventing recurrent falls and injuries were rarely provided to patients hospitalized for a first hip fracture at the time of the study. Tertiary prevention could be improved if a comprehensive geriatric assessment were systematically provided to the elderly patient hospitalized for a first hip fracture, and passive preventive measures implemente