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P. Gumbsch - One of the best experts on this subject based on the ideXlab platform.

  • Discrete dislocation simulation of plastic deformation in metal Thin Films
    Acta Materialia, 2004
    Co-Authors: Burghard Von Blanckenhagen, Eduard Arzt, P. Gumbsch
    Abstract:

    Abstract The plastic deformation of polycrystalline fcc metal Thin Films with thicknesses of 1 μm and less is investigated by simulating the dynamics of discrete dislocations in a representative columnar grain. The simulations are based on the assumption that dislocation sources or multiplication sites are rare and that every source has to operate several times to generate appreciable plastic deformation. This model is thoroughly tested by calculating the response of randomly distributed dislocation sources to an applied stress and comparing the results with experimental data. Stress–strain curves, dislocation densities, work hardening rates and their dependence on the Film thickness are calculated. The agreement between simulation and experiment is good and many aspects of Thin Film Plasticity can be understood with the assumption that small-scale plastic deformation is source controlled rather than mobility controlled.

  • Dislocation dynamics in sub-micron confinement: recent progress in Cu Thin Film Plasticity
    Zeitschrift für Metallkunde, 2002
    Co-Authors: Gerhard Dehm, B. Von Blanckenhagen, P. Gumbsch, T. J. Balk, Eduard Arzt
    Abstract:

    Abstract Small is strong – the yield stresses of Thin metall23ic Films with sub-micron thickness greatlq exceed bulc values. While it is clear that this effect must be due to confinement effects on...

  • Dislocation sources in discrete dislocation simulations of Thin-Film Plasticity and the Hall-Petch relation
    Modelling and Simulation in Materials Science and Engineering, 2001
    Co-Authors: B. Von Blanckenhagen, P. Gumbsch, Eduard Arzt
    Abstract:

    A discrete dislocation simulation has been developed to investigate Thin-Film Plasticity on a mesoscopic scale. Dislocation interactions and dislocation self-stresses are calculated wiThin the isotropic linear elasticity theory. The simulation is used to investigate the formation of dislocation pile-ups in a single columnar grain, where the boundaries are introduced as impenetrable obstacles. In analogy to the Hall-Petch model global plastic deformation is assumed to occur when the stress on the grain boundary exerted by the pile-up exceeds a certain critical value. The production of dislocations by a Frank-Read source and the dislocation evolution in the glide plane are simulated. For sources which are small compared to the grain size and for small numbers of dislocations the flow stress is well described by an analytical model of Friedman and Chrzan (1998 Phil. Mag. A 77 1185) if an appropriate Hall-Petch constant is used. If the source size scales with grain size, the flow stress depends on the inverse grain size instead of the square root of the inverse grain size below a critical size.

  • Image stresses in a free-standing Thin Film
    Modelling and Simulation in Materials Science and Engineering, 1999
    Co-Authors: A. Hartmaier, M. C. Fivel, G. R. Canova, P. Gumbsch
    Abstract:

    Three-dimensional discrete dislocation dynamics (DDD) has been used successfully to investigate different aspects of Plasticity. An investigation of Thin-Film Plasticity with the help of these DDD schemes requires detailed modelling of the interfaces and surfaces of the Film. One possible method is to compensate for the normal stresses that a dislocation population exerts on a surface by appropriate point loads. This traction compensation method is extended to a free-standing Film, where the interaction of the two opposing free surfaces must be taken into account. The influence of the free surfaces on the operation of a Frank-Read source is investigated.

  • 3D Discrete Dislocation Models of Thin-Film Plasticity
    MRS Online Proceedings Library, 1997
    Co-Authors: A. Hartmaier, M. C. Fivel, G. R. Canova, P. Gumbsch
    Abstract:

    Three-dimensional simulation schemes for discrete dislocation dynamics (DDD) have been used successfully to investigate Plasticity of bulk materials. The adaptation of these DDD schemes to a description of Thin-Film Plasticity requires detailed modeling of the interfaces and surfaces of the Film. One possible method is to compensate for the normal stresses that a dislocation distribution exerts on a surface by appropriate point loads. This traction-compensation method is extended to a free standing Film (two opposing surfaces). The extension to a Thin Film on a substrate is possible.

Eduard Arzt - One of the best experts on this subject based on the ideXlab platform.

  • A New Type of Dislocation Mechanism in UltraThin Copper Films
    MRS Online Proceedings Library, 2011
    Co-Authors: T. John Balk, Gerhard Dehm, Eduard Arzt
    Abstract:

    In this study of Thin Film Plasticity, the relationship between thermomechanical behavior and dislocation motion has been investigated in copper constrained by a silicon substrate. The stress-temperature behavior as determined from wafer curvature experiments has been directly compared to deformation microstructures observed during in situ thermal cycling of plan-view specimens in the transmission electron microscope. The flow stress of copper Films with thicknesses ranging from 100 nm to 400 nm was found to be constant, indicating that strengthening mechanisms may be saturated in this thickness regime. Moreover, unexpected dislocation glide on a plane parallel to the Film surface, which should experience no resolved shear stress, provides potential evidence for the occurrence of constrained diffusional creep in a 270 nm Film.

  • Discrete dislocation simulation of plastic deformation in metal Thin Films
    Acta Materialia, 2004
    Co-Authors: Burghard Von Blanckenhagen, Eduard Arzt, P. Gumbsch
    Abstract:

    Abstract The plastic deformation of polycrystalline fcc metal Thin Films with thicknesses of 1 μm and less is investigated by simulating the dynamics of discrete dislocations in a representative columnar grain. The simulations are based on the assumption that dislocation sources or multiplication sites are rare and that every source has to operate several times to generate appreciable plastic deformation. This model is thoroughly tested by calculating the response of randomly distributed dislocation sources to an applied stress and comparing the results with experimental data. Stress–strain curves, dislocation densities, work hardening rates and their dependence on the Film thickness are calculated. The agreement between simulation and experiment is good and many aspects of Thin Film Plasticity can be understood with the assumption that small-scale plastic deformation is source controlled rather than mobility controlled.

  • Dislocation dynamics in sub-micron confinement: recent progress in Cu Thin Film Plasticity
    Zeitschrift für Metallkunde, 2002
    Co-Authors: Gerhard Dehm, B. Von Blanckenhagen, P. Gumbsch, T. J. Balk, Eduard Arzt
    Abstract:

    Abstract Small is strong – the yield stresses of Thin metall23ic Films with sub-micron thickness greatlq exceed bulc values. While it is clear that this effect must be due to confinement effects on...

  • Dislocation sources in discrete dislocation simulations of Thin-Film Plasticity and the Hall-Petch relation
    Modelling and Simulation in Materials Science and Engineering, 2001
    Co-Authors: B. Von Blanckenhagen, P. Gumbsch, Eduard Arzt
    Abstract:

    A discrete dislocation simulation has been developed to investigate Thin-Film Plasticity on a mesoscopic scale. Dislocation interactions and dislocation self-stresses are calculated wiThin the isotropic linear elasticity theory. The simulation is used to investigate the formation of dislocation pile-ups in a single columnar grain, where the boundaries are introduced as impenetrable obstacles. In analogy to the Hall-Petch model global plastic deformation is assumed to occur when the stress on the grain boundary exerted by the pile-up exceeds a certain critical value. The production of dislocations by a Frank-Read source and the dislocation evolution in the glide plane are simulated. For sources which are small compared to the grain size and for small numbers of dislocations the flow stress is well described by an analytical model of Friedman and Chrzan (1998 Phil. Mag. A 77 1185) if an appropriate Hall-Petch constant is used. If the source size scales with grain size, the flow stress depends on the inverse grain size instead of the square root of the inverse grain size below a critical size.

  • In situ transmission electron microscopy investigation of threading dislocation motion in passivated Thin aluminum Films
    Journal of Materials Research, 1999
    Co-Authors: R.-m. Keller-flaig, Wilfried Sigle, Subra Suresh, Andrew Gouldstone, Marc Legros, Kevin J. Hemker, Eduard Arzt
    Abstract:

    In situ transmission electron microscopy (TEM) was performed to study dislocation motion during temperature cycles in aluminum Films passivated with a SiO2 layer. The Films were cycled from room temperature to 450 °C. Wedge-haped cross-sectional TEM samples were used to retain the constraint of the Si substrate. Besides interactions between dislocations and interfaces, the movement of threading dislocations wiThin the constrained aluminum Film was observed. This observation provides an experimental corroboration of the occurrence of threading dislocation motion, which is the basis for rationalizing the high-ield strength of Thin Films in available models of Thin-Film Plasticity.

Gerhard Dehm - One of the best experts on this subject based on the ideXlab platform.

  • A New Type of Dislocation Mechanism in UltraThin Copper Films
    MRS Online Proceedings Library, 2011
    Co-Authors: T. John Balk, Gerhard Dehm, Eduard Arzt
    Abstract:

    In this study of Thin Film Plasticity, the relationship between thermomechanical behavior and dislocation motion has been investigated in copper constrained by a silicon substrate. The stress-temperature behavior as determined from wafer curvature experiments has been directly compared to deformation microstructures observed during in situ thermal cycling of plan-view specimens in the transmission electron microscope. The flow stress of copper Films with thicknesses ranging from 100 nm to 400 nm was found to be constant, indicating that strengthening mechanisms may be saturated in this thickness regime. Moreover, unexpected dislocation glide on a plane parallel to the Film surface, which should experience no resolved shear stress, provides potential evidence for the occurrence of constrained diffusional creep in a 270 nm Film.

  • In situ TEM straining of single crystal Au Films on polyimide: Change of deformation mechanisms at the nanoscale
    Acta Materialia, 2007
    Co-Authors: Marc Legros, Daniel Kiener, Patric Alfons Gruber, Gerhard Dehm
    Abstract:

    Abstract In situ transmission electron microscopy straining experiments were performed on 40, 60, 80 and 160 nm thick single crystalline Au Films on polyimide substrates. A transition in deformation mechanisms was observed with decreasing Film thickness: the 160 nm thick Film deforms predominantly by perfect dislocations while Thinner Films deform mainly by partial dislocations separated by stacking faults. In contrast to the 160 nm thick Film, interfacial dislocation segments are rarely laid down by threading dislocations for the Thinner Films. At the late stages of deformation in the thicker Au Films prior to fracture, dislocations start to glide on the (0 0 1) planes (cube-glide) near the interface with the polymer substrate. The impact of size-dependent dislocation mechanisms on Thin Film Plasticity is addressed.

  • Dislocation dynamics in sub-micron confinement: recent progress in Cu Thin Film Plasticity
    Zeitschrift für Metallkunde, 2002
    Co-Authors: Gerhard Dehm, B. Von Blanckenhagen, P. Gumbsch, T. J. Balk, Eduard Arzt
    Abstract:

    Abstract Small is strong – the yield stresses of Thin metall23ic Films with sub-micron thickness greatlq exceed bulc values. While it is clear that this effect must be due to confinement effects on...

Marc Legros - One of the best experts on this subject based on the ideXlab platform.

  • In situ deformation of Thin Films on substrates.
    Microscopy research and technique, 2009
    Co-Authors: Marc Legros, Martiane Cabié, Daniel Gianola
    Abstract:

    Metallic Thin-Film Plasticity has been widely studied by using the difference between the coefficients of thermal expansion of the Film and the underlying substrate to induce stress. This approach is commonly known as the wafer curvature technique, based on the Stoney equation, which has shown that Thinner Films have higher yield stresses. The linear increase of the Film strength as a function of the reciprocal Film thickness, down to a couple hundred nanometers, has been rationalized in terms of threading and interfacial dislocations. Polycrystalline Films also show this kind of dependence when the grain size is larger than or comparable to the Film thick- ness. In situ TEM performed on plan-view or cross-section specimens faithfully reproduces the stress state and the small strain levels seen by the metallic Film during wafer curvature experi- ments and simultaneously follows the change in its microstructure. Although plan-view experi- ments are restricted to Thinner Films, cross-sectional samples where the Film is reduced to a strip (or nanowire) on its substrate are a more versatile configuration. In situ thermal cycling experi- ments revealed that the dislocation/interface interaction could be either attractive or repulsive depending on the interfacial structure. Incoherent interfaces clearly act as dislocation sinks, resulting in a dislocation density drop during thermal cycles. In dislocation-depleted Films (initially Thin or annealed), grain boundaries can compensate for the absence of dislocations by either shear- ing the Film similarly to threading dislocations or through fast diffusion processes. Conversely, dis- locations are confined inside the Film by image forces in the cases of epitaxial interfaces on hard substrates. To increase the amount of strain seen by a Film, and to decouple the effects of stress and temperature, compliant substrates can also be used as support for the metallic Film. The composite can be stretched at a given temperature using heating/cooling straining holders. Other in situ TEM methods that served to reveal scaling effects are also reviewed. Finally, an alternate method, based on a novel bending holder that can stretch metallic Films on rigid substrates, is presented. Microsc. Res. Tech. 00:000-000, 2009. V C 2009 Wiley-Liss, Inc.

  • In situ TEM straining of single crystal Au Films on polyimide: Change of deformation mechanisms at the nanoscale
    Acta Materialia, 2007
    Co-Authors: Marc Legros, Daniel Kiener, Patric Alfons Gruber, Gerhard Dehm
    Abstract:

    Abstract In situ transmission electron microscopy straining experiments were performed on 40, 60, 80 and 160 nm thick single crystalline Au Films on polyimide substrates. A transition in deformation mechanisms was observed with decreasing Film thickness: the 160 nm thick Film deforms predominantly by perfect dislocations while Thinner Films deform mainly by partial dislocations separated by stacking faults. In contrast to the 160 nm thick Film, interfacial dislocation segments are rarely laid down by threading dislocations for the Thinner Films. At the late stages of deformation in the thicker Au Films prior to fracture, dislocations start to glide on the (0 0 1) planes (cube-glide) near the interface with the polymer substrate. The impact of size-dependent dislocation mechanisms on Thin Film Plasticity is addressed.

  • In situ transmission electron microscopy investigation of threading dislocation motion in passivated Thin aluminum Films
    Journal of Materials Research, 1999
    Co-Authors: R.-m. Keller-flaig, Wilfried Sigle, Subra Suresh, Andrew Gouldstone, Marc Legros, Kevin J. Hemker, Eduard Arzt
    Abstract:

    In situ transmission electron microscopy (TEM) was performed to study dislocation motion during temperature cycles in aluminum Films passivated with a SiO2 layer. The Films were cycled from room temperature to 450 °C. Wedge-haped cross-sectional TEM samples were used to retain the constraint of the Si substrate. Besides interactions between dislocations and interfaces, the movement of threading dislocations wiThin the constrained aluminum Film was observed. This observation provides an experimental corroboration of the occurrence of threading dislocation motion, which is the basis for rationalizing the high-ield strength of Thin Films in available models of Thin-Film Plasticity.

Zhenghua Zhang - One of the best experts on this subject based on the ideXlab platform.

  • A dislocation dynamics based higher-order crystal Plasticity model and applications on confined Thin-Film Plasticity
    International Journal of Plasticity, 2011
    Co-Authors: Zhongqun Liu, Zhongbin Zhuang, Xiaoming Liu, Xue-chuan Zhao, Zhenghua Zhang
    Abstract:

    Abstract A higher-order crystal Plasticity model based on the continuum description of dislocation dynamics is developed to investigate the confined Thin-Film Plasticity at micro-scale. In this model the “back stress” and the “slip resistance” for each slip system are incorporated into a standard diffusion equation for crystal slip, which accounts for the motion of dislocations in a continuum level. Furthermore, a surface energy based interfacial model is introduced here to take account of the interaction between dislocations and the interface. It can provide a more comprehensive study of the interface effect on the confined crystal plastic behavior rather than the two extreme boundary models used in other higher-order crystal Plasticity models in which the dislocations can freely or hardly pass through the crystal interface. Then by implementing these models into finite element code the tensions of single-crystal/polycrystal Thin Al Films with passivation layers are numerically investigated. Two hardening factors associated respectively with the “back stress” and “slip resistance” are qualitatively studied, and it can be concluded from present study that the “back stress” hardening may dominate the strengthening of flow stress in confined Thin-Film Plasticity at sub-micro scale. The interfacial model is applied to successfully model the interactions of dislocation with the Film-passivation interfaces.