BEAM INDUCED VARIATIONS OF GaAs CATHODOLUMINESCENCE : EFFECT OF HYDROGEN AND DEFORMATION

We use cathodoluminescence (CL) in a scanning electron microscope to study deep level recombination in semi-insulating GaAs. Two kinds of specimens were examined (i) as-grown crystals before and after hydrogenation, (ii) crystals deformed at high temperatures before and after hydrogenation. Hydrogen is introduced into the crystal using a R.F. hydrogen plasma (T = 240°C, t = 90 min.). A consequence of the introduction of hydrogen is a substantial increase of the light emitted under the electron beam, due to a passivation of deep level center

Influence of hydrogen on minority carrier recombination at dislocations and sub-boundaries in GaAs

We have investigated by cathodoluminescence the influence of atomic hydrogen on the minority carrier recombination at dislocations and sub-boundaries in GaAs. These extended defects have been introduced by plastic deformation at high temperature. The recombining character of these defects is not qualitatively changed by hydrogen.Nous avons étudié par cathodoluminescence l'influence de l'hydrogène sur la recombinaison des porteurs minoritaires aux dislocations et aux sous-joints de grains dans GaAs. Ces défauts étendus ont été introduits par déformation plastique à chaud. Le caractère recombinant de ces défauts n'est pas qualitativement changé par l'hydrogène

Hydrogenation of GaAs covered by GaAlAs and subgrain boundary passivation

Cathodoluminescence (CL) has been performed to study the influence of hydrogen on electronic properties of GaAs with and without a GaAlAs layer. Recombination at sub-boundaries has been examined. These extended defects have been introduced by high temperature plastic deformation. The results show that they are passivated by hydrogen. The penetration of hydrogen is slowed down by the GaAlAs layer.La cathodoluminescence (CL) a été utilisée pour étudier l'influence de l'hydrogène sur les propriétés électroniques de GaAs nu et recouvert d'une couche de GaAlAs. Le caractère recombinant des sous-joints de grains a été examiné. Ces défauts étendus ont été introduits par déformation plastique à chaud. Les résultats montrent que l'hydrogène passive ces défauts. La pénétration de l'hydrogène à l'intérieur de GaAs est retardée par la présence de la couche de GaAlAs

Réactivité des petites particules métalliques de Ni° hautement dispersées sur zéolithes X échangées par des ions Ce

La composition du support zéolithique dans les systèmes Ni2+zéolithe X (acidité, présence d'autres cations) a une importance déterminante dans l'obtention d'un état métallique de nickel bien dispersé. Selon la taille des particules métalliques obtenues, le nickel présente des propriétés hydrogénolysantes, hydrogénantes et de chimisorption considérablement modifiées. Au dessous d'une certaine taille (d ≤ 12 Å), le nickel perd ses propriétés catalytiques et chimisorptives. Une étude par thermodésorption programmée de ces systèmes a mis en évidence une phase constituée "d'espèces hydrogènes" fortement chimisorbées à la surface des particules, formées lors du processus de réduction, qui inhibent tout contact entre les sites actifs du nickel et les réactifs

2012a: Genetic effects on fitness of the mutant sugary1 in wild-type maize

SUMMARY Knowing the genetic regulation of fitness is crucial for using mutants in breeding programmes, particularly when the mutant is deleterious in some genetic backgrounds, as it happens with the sweet corn mutant sugary1 (su1) in maize (Zea mays L.). The fitness and genetic effects of maize mutant su1 were monitored through five successive selfing generations in two separated mean-generation designs. The first involved two inbreds with similar genetic backgrounds, while unrelated inbreds were used for the second design. Parents, F 1 s, F 2 s, and backcrosses were crossed to P39 as the donor of su1 and the 12 crosses were successively self-pollinated for 5 years. The su1 frequency decreased linearly across selfing generations in both designs. Additive effects were significant for su1 seed viability. However, dominance effects were of higher magnitude than additive effects, even though the dominance effects were not significant. Genetic effects depended on genotypes and environments. Therefore, the fitness of su1 is under genetic control, with significant additive effects due to minor contributions of multiple genes. The fitness of su1 is strongly affected by maize genotypic background and environment. It is hypothesized that genotypes could have evolutionary potential for modulating the fitness of single mutations

PbS Infrared Detectors: Experiment and Simulation

The present work deals with the characterization and simulation of lead sulfide (PbS) photoconductors infrared detectors growth by Chemical Bath Deposition (CBD) method. Three different solutions bath are used in order to explore the doping effect and oxidant agent on detection capabilities. Photoelectrical characterization indicates that detectors performances depend strongly on oxidant and doping agents. A simulation study with surface state model is also presented. The physical parameters are deduced and are found to be in agreement with those published in the literature

Dislocation multiplication in GaAs : inhibition by doping

The crystal quality improvement by electrical or isoelectronic doping of L.E.C. grown GaAs crystals is related to the thermoelastic modelling of stresses during growth. The dislocation structure in as-grown and annealed crystals is deduced, in particular with the help of the results of plastic deformation. The addition of various elements of the columns II-III-IV-V-VI in GaAs is considered and its influence on the establishment of the dislocation substructure is discussed.L'amélioration de la qualité cristalline par dopage électrique ou isoélectronique des cristaux de GaAs obtenus par la méthode L.E.C. est reliée aux modèles thermoélastiques donnant les contraintes en cours de croissance. On en déduit les structures de dislocations dans les cristaux bruts de croissance et recuits, en particulier A la lumière des r6sultats de d6formation plastique. L'addition de diff6rents éléments des colonnes II-III-IV-V-VI dans GaAs est envisagée et son influence sur les mécanismes d'établissement de la sousstructure de dislocations est discutée

Linkage disequilibrium between fitness QTLs and the sugary1 allele of maize

Understanding how biological systems evolve across changing conditions has been a crucial focus of research. Mutations change the genetic context in which genes are expressed and yet the mechanisms underlying mutation fitness are still unclear. We use the sweet corn mutant sugary1 (su1) as a model for understanding the genetic regulation of mutant fitness, focusing on the mutant × genotype interaction across diverse environments. In a previous work, we identified quantitative trait loci (QTLs) affecting fitness in a mapping population of recombinant inbred lines (RILs) derived from a cross between field corn (B73) × sweet corn (P39 or IL14h) parents; however, the epistatic effects of these QTLs on su1 fitness were not investigated. In the present study, we estimated fitness for two seed production environments. Viability of su1 is under genetic and environmental controls, regulated by multiple genes with minor contributions, and these genes depend on the genotype into which the mutation is introduced and on the environment. Some QTLs were in linkage disequilibrium with the maize gene Su1 and had epistatic effects on su1 fitness. These QTLs could be used by sweet corn breeders by combining the most favorable alleles associated with su1 viability in breeding new genotypes from field × sweet corn crosses. These results also have implications for mutagenesis breeding or genome editing because the epistatic effects of the target genome on the new alleles generated by these techniques could affect the success of the breeding program.This work was supported by the Spanish Plan for Research and Development (grant number AGL2016-77628-R); FEDER (grant number AGL2016-77628-R); and the College of Agricultural and Life Sciences (University of WisconsinMadison)