Dislocation Nucleation and Multiplication at Crack Tips in Silicon

Scandian, Chérlio; Azzouzi, Hamid; Maloufi, Nabila; Michot, G.; George, A.

doi:10.1002/(sici)1521-396x(199901)171:1<67::aid-pssa67>3.0.co;2-t

Cited by 29 publications

(24 citation statements)

References 29 publications

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“…Such defects can be preexisting ledges (8) , but may be also caused by the intersection of dislocations with the crack front (2), (7), (9) . In-situ X-Ray topography experiments in Si have shown that a single dislocation intersecting the crack front can stimulate the emission of other dislocations in an avalanche-type multiplication process (7), (9), (10) . Such dislocation sources created at the crack front by intersecting dislocations are believed to play an important role in the fracture behavior of all brittle materials.…”

Section: Introductionmentioning

confidence: 99%

Atomistic Simulations of Dislocation - Crack Interaction

Bitzek

Gumbsch

2008

JMMP

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The interaction of dislocations with a static mode I crack is studied by large scale molecular dynamics simulations. The model consists of a blunted [001](110) crack in nickel, to which after relaxation at K < K Ic the displacement field of a dislocation is added. The response of the system is monitored during its evolution in the microcanonical ensemble. The simulations allowed to identify different characteristic processes during the interaction of the impinging dislocation with the crack. In particular, stimulated dislocation emission and cross slip processes are observed to be important for the development of a plastic zone.

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Section: Introductionmentioning

confidence: 99%

Atomistic Simulations of Dislocation - Crack Interaction

Bitzek

Gumbsch

2008

JMMP

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confidence: 97%

“…Several observations support this assumption, especially for strained layers and misfit dislocations at interfaces [2,3,4]. The formation at surfaces is also relevant where large stresses exist, like near a crack [5,6,7,8,9].Since in situ experimental observations of dislocation nucleation is not yet possible due to the very small dimensions and short observation timescales, the formation of dislocations at surfaces has been mainly investigated theoretically, particularly with continuum models and elasticity theory [10,11,12]. However, in these approaches, the predicted activation energy is very large, in disagreement with experiments.…”

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confidence: 99%

Dislocation formation from a surface step in semiconductors: Anab initiostudy

et al. 2006

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The role of a simple surface defect, such as a step, for relaxing the stress applied to a semiconductor, has been investigated by means of large scale first principles calculations. Our results indicate that the step is the privileged site for initiating plasticity, with the formation and glide of 60• dislocations for both tensile and compressive deformations. We have also examined the effect of surface and step termination on the plastic mechanisms. The plasticity of semiconductors has been extensively studied for the last decades in both fundamental and applied research, leading to significant progresses in the understanding of the key mechanisms involved. Several issues remain unsolved, however, one of the most essential being the formation of dislocations in nanostructured semiconductors such as nano-grained materials, or nanolayers in heteroepitaxy, systems extensively used in devices. While in bulk materials the few native dislocations are able to multiply via Frank-Read type mechanisms to ensure plasticity, the situation is different in nanostructured materials where dimensions are too small to allow dislocation multiplication [1]. The presence of dislocations in these materials appears to be more controlled by nucleation than by multiplication processes. It has been proposed that surfaces and interfaces, which become prominent for small dimensions, play a major role. Several observations support this assumption, especially for strained layers and misfit dislocations at interfaces [2,3,4]. The formation at surfaces is also relevant where large stresses exist, like near a crack [5,6,7,8,9].Since in situ experimental observations of dislocation nucleation is not yet possible due to the very small dimensions and short observation timescales, the formation of dislocations at surfaces has been mainly investigated theoretically, particularly with continuum models and elasticity theory [10,11,12]. However, in these approaches, the predicted activation energy is very large, in disagreement with experiments. It has been proposed that surface defects, such as steps, help the formation by lowering the activation energy. This is supported by experimental facts in the context of dislocation nucleation at or near crack fronts, with dislocation sources located on the cleavage surface and coinciding with cleavage ledges [13,14,15,16]. In addition, it has been shown that, in a stressed solid, a surface step is a source of local stress concentration [17,18,19], although not as efficient as a crack tip. Therefore, a number of continuum models have been developed, taking into account the energy gain associated to the step elimination in the process of dislocation nucleation [20,21,22,23]. Atomistic calculations have also been performed for characterizing the energetics, the processes involved, and the role of surface defects [24,25,26,27,28,29,30].These studies led to a better knowledge of the dislocation formation from surface steps or cleavage ledges, but we are still far from a complete understanding of the phenomenon. Fu...

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“…These authors proposed to adapt the KosterlitzThouless instability [26,27] to treat the BDT, this instability being related to the unbinding of dislocation pairs. While some changes in their original study are called for [28,29], the discussion What we stress, first of all, is that KPV refer to a rule of thumb that in materials with low initial dislocation density, the transition temperature T BDT is roughly one-half of the melting temperature T m . In SHH [30], referring to N i as an example they consider, T BDT is quoted as 895K, to be compared with the melting temperature T m given in Table 3.2 above as 1726K.…”

Section: Brittle-to-ductile Transition In Directionally Bonded D-elecmentioning

confidence: 99%

“…Though these discussions (see also [28] and [29]) are evidently yielding further insight into the BDT, Klein and March [31] have very recently emphasized the central importance of rotationdislocations or, as alternatively termed, disclinations for the BDT. This leads naturally into the third area of chemically bonded materials to be discussed, namely graphite and silicon.…”

Section: Brittle-to-ductile Transition In Directionally Bonded D-elecmentioning

confidence: 99%

Melting and related precursor cooperative phenomena in chemically bonded assemblies

March

2006

Physics and Chemistry of Liquids

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A number of experimental studies of condensed matter assemblies with different types of chemical bonding will provide the focus of this work. Condensed compounds X(CH 3 ) 4 , with X = C, Si or Ge, are the first of such assemblies; two phase boundaries in the pressuretemperature plane being studied: melting and a solid phase boundary heralding orientational disordering of molecules still however on a lattice. Secondly, directionally bonded d-electron transition metals such as N i, P d and N b will be treated. Here, melting is the main focus, but the precursor transition is now the separation of a high-temperature ductile solid from a lower temperature mechanically brittle phase. A dislocation-mediated model of these transitions is discussed, leading into the third area of covalently bonded solids graphite and silicon. Here topological defect models again provide the focus; both dislocations and rotation-dislocations now being invoked. Some qualitative suggestions are made to interpret the melting curve of graphite subjected to high pressure. MIRAMARE -TRIESTE September 2004 BackgroundMelting models and/or criteria have a long history and, naturally enough, have often focussed on simple crystals formed from almost spherical building blocks, condensed argon being a prime example.Here our aim is different and the focus of the present study will be on chemically bonded assemblies. We have chosen three specific areas by way of illustration, namely: I) Melting and a related lower temperature phase boundary of solid X(CH 3 ) 4 : X = C, Si, Ge as a function of pressure.II) Melting and associated physical properties in d-electron transition metals, examples referred to including the body-centred-cubic (bcc) element N b and the face-centred-cubic structures of P d and N i and III) Melting transition in graphite, and quite briefly also in silicon.As to the related precursor cooperative phenomena referred to in the title of this paper, in area I this concerns the phase boundary in solid X(CH 3 ) 4 which marks the separation, prior to melting, of a low-temperature orientationally ordered molecular phase, say at a given pressure, from a phase characterized by orientational disorder, with in both cases however the molecules still attached to the sites of a crystal lattice.In area II, the precursor transition to melting, say in the bcc transition metal N b referred to above, is the so-called brittle-to-ductile transition (BDT). A rule of thumb sometimes used by materials scientists, and detailed further below, at atmospheric pressure, relates grossly the temperature of this transition denoted by T BDT , to a fraction of the melting temperature T m .As to the third area, silicon is possibly the elemental solid in which the BDT has been most carefully studied experimentally. However, although a BDT seems not to have been observed at the time of writing in graphite, for presentational purposes a single graphene layer consisting of hexagons of C atoms with sp 2 hybridization provides a most useful starting point.With this ba...

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Dislocation Nucleation and Multiplication at Crack Tips in Silicon

Cited by 29 publications

References 29 publications

Atomistic Simulations of Dislocation - Crack Interaction

Atomistic Simulations of Dislocation - Crack Interaction

Dislocation formation from a surface step in semiconductors: Anab initiostudy

Melting and related precursor cooperative phenomena in chemically bonded assemblies

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