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2015 | Buch

Probing Crystal Plasticity at the Nanoscales

Synchrotron X-ray Microdiffraction

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Über dieses Buch

This Brief highlights the search for strain gradients and geometrically necessary dislocations as a possible source of strength for two cases of deformation of materials at small scales: nanoindented single crystal copper and uniaxially compressed single crystal submicron gold pillars.

When crystalline materials are mechanically deformed in small volumes, higher stresses are needed for plastic flow. This has been called the "Smaller is Stronger" phenomenon and has been widely observed. studies suggest that plasticity in one case is indeed controlled by the GNDs (strain gradient hardening), whereas in the other, plasticity is not controlled by strain gradients or sub-structure hardening, but rather by dislocation source starvation, wherein smaller volumes are stronger because fewer sources of dislocations are available (dislocation starvation hardening).

Inhaltsverzeichnis

Frontmatter
Chapter 1. Introduction
Abstract
Small scale plasticity plays an important role in the modern electronics. The µSXRD technique offers the unique capability to study the plastic evolution of the grains in the interconnect lines during electromigration (in situ) at the submicron resolution. These experiments provide useful insights and may also provide important practical implications, as will be discussed in greater detail, for the fundamental understanding of the electromigration degradation mechanisms, as well as for the industry critical assessment methodologies of electromigration device lifetime. The technique can also be used to provide the key tool to probe the plastic behavior of the materials at small scales under the mechanical load. Understanding and controlling plasticity and the mechanical properties of materials on this scale could thus lead to new and more robust nanomechanical structures and devices.
Arief Suriadi Budiman
Chapter 2. Synchrotron White-Beam X-ray Microdiffraction at the Advanced Light Source, Berkeley Lab
Abstract
The µSXRD technique is developed at the Advanced Light Source, Berkeley Lab. The technique can provide a local information about the crystal structure of materials in a microscale. This became possible due to the focusing of X-rays into a micron size spot. The numerical analysis of the X-ray diffraction allows to find and quantify not only the crystal structure and lattice parameters, but also the density of geometrically necessary dislocation density, crystal bending, polygonization and rotation, and local stress/strain probing at different conditions. The physical components of the experimental setup and the experimental procedure are also described in details in this chapter.
Arief Suriadi Budiman
Chapter 3. Electromigration-Induced Plasticity in Cu Interconnects: The Length Scale Dependence
Abstract
The early stage of electromigration in Cu interconnects, before the visible structural damage is discussed in this chapter. It is shown, through the μSXRD technique that plastic deformation occurs on the early stage of electromigration. The behavior of the deformation depends on the interconnect width (the crystal grains are mainly rotating in the narrow lines, while crystal bending is observed in the wider lines). Moreover, in the case of wide interconnects, the direction of bending axis is very close to the direction of electrical current.
Arief Suriadi Budiman
Chapter 4. Electromigration-Induced Plasticity in Cu Interconnects: The Texture Dependence
Abstract
The discussion of the peculiarities of electromigration in Cu interconnects is continued in this chapter. It is shown that the interconnect texture is an important factor, governing the plastic response of Cu grains to the electrical current. The degree of the plastic response is proportional with the availability of 〈112〉 direction in Cu crystals along the direction of the current. Hence, (111) out-of-plane orientation of Cu grains increases the plastic effect of electromigration, while the presence of the grains with a different orientation could weaken it.
Arief Suriadi Budiman
Chapter 5. Industrial Implications of Electromigration-Induced Plasticity in Cu Interconnects: Plasticity-Amplified Diffusivity
Abstract
The theoretical analysis of the diffusion in interconnects during the electromigration is performed in this chapter. Two main diffusion paths are compared: grain boundaries and electromigration induced dislocations. The electromigration induced dislocations are formed due to the crystal bending, described in the previous chapters, and form a short diffusion path in the direction of the current. These two possible diffusion paths can lead to the significantly different device failure time dependence on the current density. This can lead to an important implication for the way device lifetime/reliability is assessed.
Arief Suriadi Budiman
Chapter 6. Indentation Size Effects in Single Crystal Cu as Revealed by Synchrotron X-ray Microdiffraction
Abstract
The observation of Laue peak streaking near small indentations in the (111) surface of a copper single crystal is described. The geometrically necessary dislocation (GND) density is computed from the µSXRD data for a different indentation depths. It is shown that GND density increases with decreasing indentation depth, which is in agreement with a revised Nix-Gao model. This finding supports that the indentation size effect is associated with geometrically necessary dislocations and related strain gradients.
Arief Suriadi Budiman
Chapter 7. Smaller is Stronger: Size Effects in Uniaxially Compressed Au Submicron Single Crystal Pillars
Abstract
A study of submicron single crystal Au pillar, before and after uniaxial plastic deformation, is discussed in this chapter. There is no evidence of measurable lattice rotation or lattice bending/polygonization due to the deformation up to a plastic strain of about 35 % and a flow stress of close to 300 MPa. These observations, coupled with other examinations using electron microscopy, suggest that plasticity here is not controlled by strain gradients, but rather by dislocation source starvation.
Arief Suriadi Budiman
Chapter 8. Conclusions
Abstract
Our present understanding of the electromigration-induced plasticity, indentation size effect, and small-scale plasticity at the uniaxial compressive stress are summarized in this chapter.
Arief Suriadi Budiman
Metadaten
Titel
Probing Crystal Plasticity at the Nanoscales
verfasst von
Arief Suriadi Budiman
Copyright-Jahr
2015
Verlag
Springer Singapore
Electronic ISBN
978-981-287-335-4
Print ISBN
978-981-287-334-7
DOI
https://doi.org/10.1007/978-981-287-335-4

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