Optical properties of ZnO nanowire arrays electrodeposited on n-and p-type Si(1 1 1): Effects of thermal annealing

a b s t r a c t Electrodeposition is a low temperature and low cost growth method of high quality nanostructured active materials for optoelectronic devices. We report the electrochemical preparation of ZnO nanorod/nanowire arrays on n-Si(1 1 1) and p-Si(1 1 1). The effects of thermal annealing and type of substrates on the optical properties of ZnO nanowires electroplated on silicon (1 1 1) substrate are reported. We fabricated ZnO nanowires/p-Si structure that exhibits a strong UV photoluminescence emission and a negligible visible emission. This UV photoluminescence emission proves to be strongly influenced by the thermal annealing at 150-800 • C. Photo-detectors have been fabricated based on the ZnO nanowires/p-Si heterojunction

Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale(1-3). Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter(4); identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation(5,6); analyses timings and patterns of tumour evolution(7); describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity(8,9); and evaluates a range of more-specialized features of cancer genomes(8,10-18).Peer reviewe

Exploring AgBixI3x+1 semiconductor thin films for lead-free perovskite solar cells

International audienc

Electrocrystallization of Epitaxial Zinc Oxide onto Gallium Nitride

International audienceWe have studied in detail the structure and the nucleation and growth process of electrodeposited epitaxial hexagonal ZnO on GaN(0001). The crystallites grow with the c-axis perpendicular to substrate and the in-plane relationship is ZnO[100] || GaN[100]. We show that the deposit aspect progressively changes with the deposition time from isolated dispersed dots toward fully covering flat zinc oxide single crystals. A simple model is presented which explains these morphological changes. The nucleation is instantaneous and the growth rate is controlled by the crystal surface reactions. The velocity of crystal growth is found dependent on the crystallographic face of the grain: it is approximately five times faster on the {0001} planes than on the {101̄0} and {011̄0} families of planes. We show that nucleation problems are encountered with high-quality GaN presenting a low surface defect density. The difficulty has been overcome by chemically treating the substrate with an aqueous ammonium hydroxide solution prior to the deposition. This treatment allows the nucleation of zinc oxide but has a detrimental effect on the deposit “mosaicity” which is better in the case of GaN with high defect density

Electrodeposition Process Modelling Using Continuous And Discrete Scales

International audienc

Electrodeposition Process Modelling Using Continuous And Discrete Scales

International audienc

Upconversion emission investigation of Tb3+/Yb3+ codoped CdF2 single crystals under infrared laser pump

International audienc

Optical Properties Of Zno Nanowire Arrays Electrodeposited On N- And P-Type Si(1 1 1): Effects Of Thermal Annealing

Electrodeposition is a low temperature and low cost growth method of high quality nanostructured active materials for optoelectronic devices. We report the electrochemical preparation of ZnO nanorod/nanowire arrays on n-Si(1 1 1) and p-Si(1 1 1). The effects of thermal annealing and type of substrates on the optical properties of ZnO nanowires electroplated on silicon (1 1 1) substrate are reported. We fabricated ZnO nanowires/p-Si structure that exhibits a strong UV photoluminescence emission and a negligible visible emission. This UV photoluminescence emission proves to be strongly influenced by the thermal annealing at 150-800 °C. Photo-detectors have been fabricated based on the ZnO nanowires/p-Si heterojunction. © 2011 Elsevier B.V. All rights reserved

Highly Sensitive And Selective Hydrogen Single-Nanowire Nanosensor

Metal oxides such as ZnO have been used as hydrogen sensors for a number of years. Through doping, the gas response of zinc oxide to hydrogen has been improved. Cadmium-doped ZnO nanowires (NWs) with high aspect ratio have been grown by electrodeposition. Single doped ZnO NWs have been isolated and contacted to form a nanodevice. Such nanosystem demonstrates an enhanced gas response and selectivity for the detection of hydrogen at room temperature compared to previously reported H 2 nanosensors based on pure single-ZnO NWs or multiple NWs. A dependence of the gas response of a single Cd-ZnO nanowire on the NW diameter and Cd content was observed. It is shown that cadmium-doping in single-crystal zinc oxide NWs can be used to optimize their response to gases without the requirement of external heaters. The sensing mechanisms responsible for such improved response to hydrogen are discussed. © 2012 Elsevier B.V

Effects of TiO₂ nanoparticle polymorphism on dye-sensitized solar cell photovoltaic properties

International audienceWe present a joined experimental and theoretical investigation of the TiO2 polymorphism effects on dye-sensitized solar cells (DSSCs) photovoltaic properties. TiO2 nanoparticles of pure anatase, pure rutile and pure brookite stabilized phases with various sizes have been prepared by solution sol–gel approaches in order to evaluate their properties in photovoltaic devices. For a valuable comparison, these various nanoparticles have been used to construct identical solar cells. Their properties have been thoroughly estimated and analysed by J–V curves and impedance spectroscopy measurements along with first-principles calculations based on the density functional theory (DFT) under the B3LYP approximation. In the light of DFT calculations, the open circuit voltage (Voc) behavior of the solar cells is mainly explained by the dependency of the bottom of the conduction band position on the TiO2 phase. Quantifications of electron lifetimes, transfer times, diffusion coefficients (Deff) in the various polymorph TiO2 photoanodes are also of particular importance for explaining the photovoltaic properties of the different DSSCs. We have notably found a conductivity and Deff order being rutile < brookite < anatase. The comparison of anatase and brookite based-cells shows that the latter phase is very interesting for the considered application