Deactivation of electrically supersaturated Te-doped InGaAs grown by MOCVD

Achieving and sustaining the highest doping level possible in InGaAs is critical for the reduction of contact resistance in future microelectronic applications. Tellurium (Te) is a very promising n-type dopant with high reported n-type doping densities. However, the stability of this dopant during post-growth thermal processing is unknown. Supersaturated Te-doped InGaAs layers were grown by MOCVD at 500 °C. The electrically active concentration of Te doping was 4.4 × 1019 cm−3 as grown. The thermal stability of the Te was investigated by studying the effect of post-growth annealing between 550 and 700 °C on the electrical activation. At all temperatures, the electrical activation decreased from its starting electron concentration of 4.4 × 1019 cm−3 down to 6–7 × 1018 cm−3. The rate of deactivation was measured at each temperature, and the activation energy for the deactivation process was determined to be 2.6 eV. The deactivation could be caused by either Te–Te clustering or a Te-point defect reaction. HAADF-STEM images showed no visible clustering or precipitation after deactivation. Based on previous ab initio calculations that suggest the VIII population increases as the Fermi level moves toward the conduction band, it is proposed that formation of isolated point defect complexes, possibly a Te–VIII complex, is associated with the deactivation process

GaAs on Si epitaxy by aspect ratio trapping: analysis and reduction of defects propagating along the trench direction

The Aspect Ratio Trapping technique has been extensively evaluated for improving the quality of III-V heteroepitaxial films grown on Si, due to the potential for terminating defects at the sidewalls of SiO2 patterned trenches that enclose the growth region. However, defects propagating along the trench direction cannot be effectively confined with this technique. We studied the effect of the trench bottom geometry on the density of defects of GaAs fins, grown by metal-organic chemical vapor deposition on 300 mm Si (001) wafers inside narrow (<90 nm wide) trenches. Plan view and cross sectional Scanning Electron Microscopy and Transmission Electron Microscopy, together with High Resolution X-Ray Diffraction, were used to evaluate the crystal quality of GaAs. The prevalent defects that reach the top surface of GaAs fins are {111} twin planes propagating along the trench direction. The lowest density of twin planes, 8 108 cm 2, was achieved on “V” shaped bottom trenches, where GaAs nucleation occurs only on {111} Si planes, minimizing the interfacial energy and preventing the formation of antiphase boundaries

Critical evaluation of starch-based antibacterial nanocomposites as agricultural mulch films: Study on their interactions with water and light

In order to evaluate the potentiality of novel formulations based on starch to be used as agricultural mulch films, native and oxidized corn starch nanocomposites were prepared by extrusion using natural (Bent) and chitosan-modified bentonite (Bent-CS) fillers. The nanocomposite interactions with water were studied by means of moisture content (MC) determination, water solubility (WS), water vapor permeability (WVP), and contact angle (CA). The light transmission spectra were analyzed in order to determine the transparency and radiometric properties of films. Mechanical properties are also included and related with the cryo-fractured surface morphology observed by scanning electron microscopy (SEM). Finally, the antimicrobial action of developed nanocomposites was investigated against the phytopathogen bacterium Pseudomonas syringae pv tomato DC3000 (Psy). Results suggest that starch oxidation leads to a reduction in polarity and transparency. The incorporation of nanoclays improved water resistance but did not produce a significant effect in WVP and mechanical properties, and new strategies are required to improve the nanocomposite performance. However, the incorporation of Bent-CS exerted antibacterial activity on nanocomposites, which is an encouraging result.Fil: Merino, Danila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Gutiérrez Carmona, Tomy José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Mansilla, Andrea Yamila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Casalongue, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Alvarez, Vera Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

An overview of the plant response to pathogen attack: chitosan as a general elicitor of induced resistance in plants.

Plant disease resistance is the ability of a plant to prevent or restrict pathogen growth and multiplication. All plants, whether they are resistant or susceptible, respond to pathogen attack by the induction of coordinate signalling system, which required the accumulation of different gene products. In plant immunity general elicitors, including chitin/chitosan oligomers are able to induce host defence response by binding to specific molecule

Effect of chitosan seed treatment as elicitor of resistance to Fusarium graminearum in wheat.

The potential ability of chitosan seed treatment to induce resistance in plants of durum wheat (Triticum durum) against the seed borne fungal pathogen Fusarium graminearum, one of the main causal agents of root and foot rot in wheat, was evaluated. The chitosan seed treatment efficacy was evaluated by biochemical analyses, comparing: seed treated, seed treated and inoculated with the fungus, seed not treated and inoculated, seeds not treated and not inoculated. The enzymatic activities of some enzymes involved in defense mechanisms were analysed: guaiacol peroxidase (POD), ascorbate peroxidase (APX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL), as well as the phenol content. Seed treatment induced changes in the enzymatic activities and increased phenol production. Greenhouse trials were performed with inoculated soil and the disease incidence on the plants was significantly reduced by chitosan seed treatment. Finally, field trials were conducted with inoculated seeds and then treated with chitosan. The chitosan seed treatment induced a decrease in disease severity and enhanced quantitative yield parameters, suggesting the possibility of the use of chitosan as a seed treatment in crop protection in order to improve the plant defense response

Chitosan in Agriculture: A New Challenge for Managing Plant Disease

In recent years, environmental friendly measures have been developed for managing crop diseases as alternative to chemical pesticides, including the use of natural compounds such as chitosan. In this chapter, the common uses of this natural product in agriculture and the potential uses in plant disease control are reviewed. The last advanced researches as seed coating, plant resistance elicitation and soil amendment applications are also described. Chitosan is a deacetylated derivative of chitin, that is naturally present in the fungal cell wall and in crustacean shells from which it can be easily extracted. Chitosan have been reported to possess antifungal and antibacterial activity and it showed to be effective against seed-borne pathogens when applied as seed treatment. It can form physical barriers (film) around the seed surface and it can vehicular other antimicrobial compounds that could be added to the seed treatments. Chitosan behaves as a resistance elicitor inducing both local and systemic plant defense responses even when applied to the seeds. The chitosan used as soil amendment was shown to give many benefits to different plant species by reducing the pathogen attack and infection. Concluding, the chitosan is an active molecule that finds many possibilities for application in agriculture, including plant disease control

An overview of the plant response to pathogen attack: chitosan as a general elicitor of induced resistance in plants.

Plant disease resistance is the ability of a plant to prevent or restrict pathogen growth and multiplication. All plants, whether they are resistant or susceptible, respond to pathogen attack by the induction of coordinate signalling system, which required the accumulation of different gene products. In plant immunity general elicitors, including chitin/chitosan oligomers are able to induce host defence response by binding to specific molecule