Energy levels distribution in supersaturated silicon with titanium for photovoltaic applications

In the attempt to form an intermediate band in the bandgap of silicon substrates to give it the capability to absorb infrared radiation, we studied the deep levels in supersaturated silicon with titanium. The technique used to characterize the energy levels was the thermal admittance spectroscopy. Our experimental results showed that in samples with titanium concentration just under Mott limit there was a relationship among the activation energy value and the capture cross section value. This relationship obeys to the well known Meyer-Neldel rule, which typically appears in processes involving multiple excitations, like carrier capture/emission in deep levels, and it is generally observed in disordered systems. The obtained characteristic Meyer-Neldel parameters were Tmn = 176 K and kTmn = 15 meV. The energy value could be associated to the typical energy of the phonons in the substrate. The almost perfect adjust of all experimental data to the same straight line provides further evidence of the validity of the Meyer Neldel rule, and may contribute to obtain a deeper insight on the ultimate meaning of this phenomenon. (C) 2015 AIP Publishing LLC

Sub-bandgap spectral photo-response analysis of Ti supersaturated Si

We have analyzed the increase of the sheet conductance (ΔG□) under spectral illumination in high dose Ti implanted Si samples subsequently processed by pulsed-laser melting. Samples with Ti concentration clearly above the insulator-metal transition limit show a remarkably high ΔG□, even higher than that measured in a silicon reference sample. This increase in the ΔG□ magnitude is contrary to the classic understanding of recombination centers action and supports the lifetime recovery predicted for concentrations of deep levels above the insulator-metal transition

Ruling out the impact of defects on the below band gap photoconductivity of Ti supersaturated Si

In this study, we present a structural and optoelectronic characterization of high dose Ti implanted Si subsequently pulsed-laser melted (Ti supersaturated Si). Time-of-flight secondary ion mass spectrometry analysis reveals that the theoretical Mott limit has been surpassed after the laser process and transmission electron microscopy images show a good lattice reconstruction. Optical characterization shows strong sub-band gap absorption related to the high Ti concentration. Photoconductivity measurements show that Ti supersaturated Si presents spectral response orders of magnitude higher than unimplanted Si at energies below the band gap. We conclude that the observed below band gap photoconductivity cannot be attributed to structural defects produced by the fabrication processes and suggest that both absorption coefficient of the new material and lifetime of photoexcited carriers have been enhanced due to the presence of a high Ti concentration. This remarkable result proves that Ti supersaturated Si is a promising material for both infrared detectors and high efficiency photovoltaic devices

Scaf1 promotes respiratory supercomplexes and metabolic efficiency in zebrafish

The oxidative phosphorylation (OXPHOS) system is a dynamic system in which the respiratory complexes coexist with superassembled quaternary structures called supercomplexes (SCs). The physiological role of SCs is still disputed. Here, we used zebrafish to study the relevance of respiratory SCs. We combined immunodetection analysis and deep data-independent proteomics to characterize these structures and found similar SCs to those described in mice, as well as novel SCs including III2 + IV2, I + IV, and I + III2 + IV2. To study the physiological role of SCs, we generated two null allele zebrafish lines for supercomplex assembly factor 1 (scaf1). scaf1 / fish displayed altered OXPHOS activity due to the disrupted interaction of complexes III and IV. scaf1 / fish were smaller in size and showed abnormal fat deposition and decreased female fertility. These physiological phenotypes were rescued by doubling the food supply, which correlated with improved bioenergetics and alterations in the metabolic gene expression program. These results reveal that SC assembly by Scaf1 modulates OXPHOS efficiency and allows the optimization of metabolic resources.Microscopy Imaging Center of the University of BernSpanish Ministry of Economy and Competitiveness, MINECO SAF2015-65633-RSpanish Ministry of Economy and Competitiveness, MINECO SAF2015-65633-RHuman Frontier Science Program RGP0016/2018European Research Council (ERC) 337703SNF 31003A-159721Swiss National Science Foundation (SNSF) 320030_170062MINECO BIO2015-67580-PCarlos III Institute of Health-Fondo de Investigacion Sanitaria) PRB3 IPT17/0019Fundacion La Marato TV3La Caixa Foundation HR17-00247Ministry of Economy, Industry and Competitiveness (MEIC)Pro-CNIC FoundationSevero Ochoa Center of Excellence (MEIC award) SEV-2015-050