Intermediate band formation on silicon layers for solar cell applications was achieved by titanium implantation and laser annealing. A two-layer heterogeneous system, formed by the implanted layer and by the un-implanted substrate, was formed. In this work, we present for the first time electrical characterization results which show that recombination is suppressed when the Ti concentration is high enough to overcome the Mott limit, in agreement with the intermediate band theory. Clear differences have been observed between samples implanted with doses under or over the Mott limit. Samples implanted under the Mott limit have capacitance values much lower than the un-implanted ones as corresponds to a highly doped semiconductor Schottky junction. However, when the Mott limit is surpassed, the samples have much higher capacitance, revealing that the intermediate band is formed. The capacitance increasing is due to the big amount of charge trapped at the intermediate band, even at low temperatures. Ti deep levels have been measured by admittance spectroscopy. These deep levels are located at energies which vary from 0.20 to 0.28 eV below the conduction band for implantation doses in the range 10 13 -10 14 at./cm 2 . For doses over the Mott limit, the implanted atoms become nonrecombinant. Capacitance voltage transient technique measurements prove that the fabricated devices consist of two-layers, in which the implanted layer and the substrate behave as an n þ /n junction. V C 2013 American Institute of Physics. [http://dx

Three tapered silica optical fibers, uncoated and coated with metallic (Al or Cu) and dielectric layers (TiO2), are employed to determine the presence of oil and Hazardous and Noxious Substances (HNS from now on) in water, by means of the measurement of their spectral transmittance. With our experimental assembly, the presence of oil and HNS spills can be detected employing the three different kinds of tapers, since the complete range of refractive indices of the pollutants (1.329–1.501) is covered with these tapers. The most suitable spectral range to detect the presence of a chemical pollutant in seawater has been identified and a complete spectral characterization of the three types of optical fiber tapers has been carried out. The results obtained show that, in general terms, these devices working together can be employed for the early detection of oil and HNS spills in seawater in a marine industrial environment. These sensors have many advantages, such as its low cost, its simplicity and versatility (with interesting properties as quick response and repeatability), and especially that they can be self-cleaned with seawater in motion.

Abstract. Intermediate band silicon solar cells have been fabricated by Titanium ion implantation and laser annealing. A two-layer heterogeneous system, formed by the implanted layer and by the unimplanted substrate is obtained. In this work we present electrical characterization results which evidence the formation of the intermediate band on silicon when ion implantation dose is beyond the Mott limit. Clear differences have been observed between samples implanted with doses under or over the Mott limit. Samples implanted under the Mott limit have capacitance values much lower than the non-implanted ones as corresponds to a highly doped semiconductor Schottky junction. However, when the Mott limit is surpassed the samples have much higher capacitance, revealing that the intermediate band is formed. The capacitance increase is due to the big amount of charge trapped at the intermediate band, even at low temperatures. Titanium deep levels have been measured by Admittance Spectroscopy. These deep levels are located at energies which vary from 0.20 to 0.28 eV bellow the conduction band for implantation doses in the range 10 13 -10 14 at/cm 2 . For doses over the Mott limit the implanted atoms become non recombinant. Admittance measurements are the first experimental demonstration the Intermediate Band is formation. Capacitance voltage transient technique measurements prove that the fabricated devices consist of two-layers, in which the implanted layer and the substrate behave as an n + /n junction.

ABSTRACT:We present a system for diffraction gratings engraving over cylindrical substrates. The manufacturing of the gratings is performed using a Q-switched nanosecond pulsed laser. We have used a mechanical system with six motorized stages. Five of them are linear stages, and the other one is a high precision rotator. The assembly also comprises various devices that monitorize in real time the manufacturing process. A home-made software synchronizes and controls the entire system.

The ambient air pollution of nano- and micrometric sized particles produced during a rastering process is measured and analyzed together with the topographic measurements of the rastered surface on sheets of stainless steel samples. The rastering process performed consisted of carrying out ablation with consecutive nanosecond infrared laser pulses along parallel lines. The topographic measurements and the measurements of the air concentration of the total active surface of the nanoparticles as well as the number of micrometric particles generated during 1 min of the rastering process were measured for different adjustments of the laser power, pulse frequency, and scan velocity. Exposure to very high nanoparticulate air concentration was measured, which is a health risk that should be avoided. The laser power should be reduced as much as possible to minimize the air pollution, and by analyzing the surface finish of the rastered surfaces, it was observed that the main factor that provided the best finish quality was not the laser power (i.e., the adjustable pump intensity) but the number of pulses in the same place (Np) and the scan velocity. In particular, the best finish quality was obtained at the highest scan velocity used (100 mm/s) and Np = 15.