Internal friction study on the mobility of screw dislocations in undoped InSb

Dislocation mobility is studied by low frequency internal friction in undoped InSb between 0.1 and 0.98 Tm. Samples characterized by a mainly screw dislocations substructure generated by low temperature (403 K) deformation, reveal two high amplitude peaks located at 570 and 725 K. The 570 K-peak symmetrically shaped is explained as an intrinsic relaxation peak of screw dislocations moving by double kink nucleation followed by their lateral propagation. The peak analysis leads to an activation energy 1.27 ± 0.11 eV, close to the apparent activation energy of the InSb plastic deformation.La mobilité des dislocations a été étudiée dans InSb non dopé par frottement intérieur basse fréquence (1 Hz) entre 0,1 et 0,98 Tm. Avec une sous-structure composée essentiellement de dislocations vis engendrée par déformation plastique à 403 K, on a mis en évidence deux pics d'amplitude importante situés à 570 K et 725 K. Le pic à 570 K, d'allure symétrique, est interprété comme un pic de relaxation intrinsèque de dislocations vis par nucléation de doubles décrochements, suivie de la propagation latérale de chaque décrochement. L'analyse de ce pic conduit à une énergie d'activation de 1,27 ± 0,11 eV voisine de celle de la déformation plastique

Internal friction study on the mobility of screw dislocations in undoped InSb

Dislocation mobility is studied by low frequency internal friction in undoped InSb between 0.1 and 0.98 Tm. Samples characterized by a mainly screw dislocations substructure generated by low temperature (403 K) deformation, reveal two high amplitude peaks located at 570 and 725 K. The 570 K-peak symmetrically shaped is explained as an intrinsic relaxation peak of screw dislocations moving by double kink nucleation followed by their lateral propagation. The peak analysis leads to an activation energy 1.27 ± 0.11 eV, close to the apparent activation energy of the InSb plastic deformation

INTERNAL FRICTION INVESTIGATION ON THE MOBILITY OF DISLOCATIONS IN III-V COMPOUNDS

La mobilité des différents types de dislocations contrôlant la déformation des composés III-V a été étudiée par des expériences de frottement intérieur entre 0,1 et 0,98 Tm sur des monocristaux d'InSb non dopés. Les résultats originaux ont été obtenus à partir de deux sous-structures de dislocations distinctes résultant de la déformation plastique en glissement simple à deux températures différentes : à 403 K où l'on obsèrve une population à caractère vis prédominant ; à 495 K où l'on observe à la fois des dislocations vis, 60° et des dipôles coins. On a ainsi mis en évidence un pic de relaxation dû aux dislocations vis dont l'énergie d'activation 1,15 eV est très proche de celle attribuée aux mouvements des dislocations vis à partir d'autres techniques et de la déformation plastique notamment.The mobility of the different types of dislocations involved in the doformation of III-V compounds has been studied with internal friction experiments from 0.1 to 0.98 Tm in undoped InSb single crystals. Original results have been achieved wiht two distinct dislocations substructures established by single glide plastic deformation at two different temperatures : 403 K, which leads to a screw dislocation predominance ; 495 K, which leads to a mixed 60°, screw, and edge dipoles substructure. We have got a relaxation peak due to screw dislocations, with an activation energy ≈ 1.15 eV, very close to that ascribed to screw dislocation movement by other techniques (plastic deformation)

Egg pecking and puncturing behaviors in shiny and screaming cowbirds: effects of eggshell strength and degree of clutch completion

Abstract: Shiny cowbirds (Molothrus bonariensis) are generalist brood parasites that use hosts varying in body and egg size. On the contrary, screaming cowbirds (M. rufoaxillaris), which are larger than shiny cowbirds, are host specialist that use mainly one host of similar body and egg size. Both parasites peck and puncture eggs when visiting nests. Through puncturing eggs, cowbirds can reduce the competition for food their chicks face (reduction of competition hypothesis), but the same behavior could also be a mechanism to enforce host to renest when nests are found late in the nesting cycle (farming hypothesis). Eggshell strength increases the difficulty to puncture eggs and therefore may modulate egg-pecking behavior. To test these hypotheses, we studied the effect of the degree of clutch completion and egg size on egg-puncturing behavior. Moreover, we evaluated if morphological differences between cowbird species and eggshell strength affected egg-pecking behavior. We presented captive females a nest with complete (four eggs) or incomplete (one egg) clutches of house wren (small egg size, low eggshell strength), chalk-browed mockingbird (large egg size, intermediate eggshell strength), or shiny cowbird (medium egg size, high eggshell strength). The proportion of nests with punctured eggs was similar for complete and incomplete clutches. Cowbirds punctured more eggs in complete than in incomplete clutches, but in complete clutches, they did not destroy the entire clutch. There were no differences in the egg-pecking behavior between cowbird species, which pecked more frequently the eggs with the strongest eggshell. Our findings are consistent with the reduction of competition hypothesis. Significance statement: Brood parasitic birds do not build nests and raise their chicks. Instead, they lay eggs in nests of other species (hosts), which carry out all parental care. Some brood parasites, like the cowbirds, peck and puncture eggs when they visit host nests. This behavior may help to reduce the competition for food that their chicks face in the nest (reduction of competition hypothesis) or may enforce hosts to renest (farming hypothesis). We experimentally studied egg-pecking and egg-puncturing behaviors in the host generalist shiny cowbird and the host specialist screaming cowbird. We found that the degree of clutch completion and egg size modulate egg-puncturing behavior and eggshell strength modulates egg-pecking behavior. Our results indicate that by puncturing eggs, cowbirds reduce nest competition.Fil: Cossa, Natalia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Tuero, Diego Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Reboreda, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Fiorini, Vanina Dafne. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentin

Sensing and MEMS Devices in Thin-Film SOI MOS Technology

Silicon-on-Insulator (SOI) technology is emerging as a major contender for heterogeneous microsystems applications. In this work, we demonstrate the advantages of SOI technology for building thin-film field-effect biosensors and optical detectors, physical and chemical sensors on thin dielectric membrane as well as three-dimensional (3D) microelectromechanical (MEMS) sensors and actuators. The flatness and robustness of the thin membrane as well as the self-assembling of 3D microstructures rely on the chemical release of the microstructures and on the control of the residual stresses building up in multilayered structures undergoing a complete thermal process. The deflection of multilayered structures made of both elastic and plastic thin films results from the thermal expansion coefficient mismatches between the layers and from the plastic flow of a metallic layer. The proposed CMOS-compatible fabrication processes were successfully applied to suspended sensors on thin dielectric membranes such as gas-composition, gas-flow and pressure sensors and to 3D self-assembled microstructures such as thermal and flow sensors