Superconductivity in Silicon Nanostructures

We present the findings of the superconductivity in the silicon nanostructures prepared by short time diffusion of boron after preliminary oxidation of the n-type Si (100) surface. These Si-based nanostructures represent the p-type high mobility silicon quantum well (Si-QW) confined by the delta - barriers heavily doped with boron. The ESR studies show that the delta - barriers appear to consist of the trigonal dipole centers, B(+)-B(-), which are caused by the negative-U reconstruction of the shallow boron acceptors, 2B(0)=>B(+)-B(-). The temperature and magnetic field dependencies of the resistance, thermo-emf, specific heat and magnetic susceptibility demonstrate that the high temperature superconductivity observed seems to result from the transfer of the small hole bipolarons through these negative-U dipole centers of boron at the Si-QW - delta - barrier interfaces. The value of the superconductor energy gap obtained is in a good agreement with the data derived from the oscillations of the conductance in normal state and of the zero-resistance supercurrent in superconductor state as a function of the bias voltage. These oscillations appear to be correlated by on- and off-resonance tuning the two-dimensional subbands of holes with the Fermi energy in the superconductor delta - barriers. Finally, the proximity effect in the S- Si-QW -S structure is revealed by the findings of the multiple Andreev reflection (MAR) processes and the quantization of the supercurrent

Genome wide linkage study, using a 250K SNP map, of Plasmodium falciparum infection and mild malaria attack in a Senegalese population

Multiple factors are involved in the variability of host's response to P. falciparum infection, like the intensity and seasonality of malaria transmission, the virulence of parasite and host characteristics like age or genetic make-up. Although admitted nowadays, the involvement of host genetic factors remains unclear. Discordant results exist, even concerning the best-known malaria resistance genes that determine the structure or function of red blood cells. Here we report on a genomewide linkage and association study for P. falciparum infection intensity and mild malaria attack among a Senegalese population of children and young adults from 2 to 18 years old. A high density single nucleotide polymorphisms (SNP) genome scan (Affimetrix GeneChip Human Mapping 250K-nsp) was performed for 626 individuals: i.e. 249 parents and 377 children out of the 504 ones included in the follow-up. The population belongs to a unique ethnic group and was closely followed-up during 3 years. Genome-wide linkage analyses were performed on four clinical and parasitological phenotypes and association analyses using the family based association tests (FBAT) method were carried out in regions previously linked to malaria phenotypes in literature and in the regions for which we identified a linkage peak. Analyses revealed three strongly suggestive evidences for linkage: between mild malaria attack and both the 6p25.1 and the 12q22 regions (empirical p-value = 5 x 10(-5) and 96 x 10(-5) respectively), and between the 20p11q11 region and the prevalence of parasite density in asymptomatic children (empirical p-value = 1.5 x 10(-4)). Family based association analysis pointed out one significant association between the intensity of plasmodial infection and a polymorphism located in ARHGAP26 gene in the 5q31-q33 region (p-value = 3.7 x 10(-5)). This study identified three candidate regions, two of them containing genes that could point out new pathways implicated in the response to malaria infection. Furthermore, we detected one gene associated with malaria infection in the 5q31-q33 region

Modification of Light Emission in Si-Rich Silicon Nitride Films Versus Stoichiometry and Excitation Light Energy

International audienc

Evaluation of the effective quantum efficiency of photon conversion layers placed on solar cells

Équipe 104 : NanomatériauxInternational audiencePhoton conversion layers are a possible way of improving the efficiency of existing solar cells, even above the Shockley-Queisser limit. The related concepts are often called downshifting, downconversion, and upconversion. Despite the variety of photon conversion systems proposed in the literature, understanding their real impact is often difficult due to joint effects. Here, a new methodology is provided to analyse the efficiency of such conversion layers and to be able to compare the different systems proposed

Moderate temperature deposition of RF magnetron sputtered SnO2-based electron transporting layer for triple cation perovskite solar cells

Abstract The perovskite solar cells (PSCs) are still facing the two main challenges of stability and scalability to meet the requirements for their potential commercialization. Therefore, developing a uniform, efficient, high quality and cost-effective electron transport layer (ETL) thin film to achieve a stable PSC is one of the key factors to address these main issues. Magnetron sputtering deposition has been widely used for its high quality thin film deposition as well as its ability to deposit films uniformly on large area at the industrial scale. In this work, we report on the composition, structural, chemical state, and electronic properties of moderate temperature radio frequency (RF) sputtered SnO2. Ar and O2 are employed as plasma-sputtering and reactive gases, respectively. We demonstrate the possibility to grow a high quality and stable SnO2 thin films with high transport properties by reactive RF magnetron sputtering. Our findings show that PSC devices based on the sputtered SnO2 ETL have reached a power conversion efficiency up to 17.10% and an average operational lifetime over 200 h. These uniform sputtered SnO2 thin films with improved characteristics are promising for large photovoltaic modules and advanced optoelectronic devices