Article

International Journal of Fracture

, Volume 140, Issue 1, pp 125-140

First online:

Energy considerations in crack deflection phenomenon in single crystal silicon

  • Dov ShermanAffiliated withDepartment of Materials Engineering, Technion-Israel Institute of Technology Email author 

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Abstract

Crack deflection in single-crystal brittle occurs when a crack, propagating on one cleavage plane, ‘chooses’, from energy considerations, to continue propagating on another cleavage plane. This phenomenon was identified during dynamic crack propagation experiments of thin, rectangular [0 0 1] single-crystal (SC) silicon specimens subjected to three-point bending (3PB). Specimens with long pre-cracks (hence propagating at a ‘low’ energy and velocity) cleave along the vertical (1 1 0) plane, while the same specimens but with short pre-cracks (and therefore with higher propagation energy and velocity) cleave along the inclined (1 1 1) plane. The same specimens with intermediate pre-crack length show that the crack first propagates on the (1 1 0) plane and then deflects to the (1 1 1) plane. We show that the deflection is due to variations of the material property that resists cracking, Γ, the dynamic cleavage energy, with velocity and crystallographic orientation. We propose selection criteria to explain the deflection: The crack will deflect to the plane with the lowest dynamic cleavage energy. We further suggest that crack deflection is the basic mechanism controlling the way the crack consumes energy while propagating and is the main cause of surface perturbations. The spatial temporal fracture energy along the (1 1 0) cleavage plane is evaluated.

Keywords

Dynamic fracture Single-crystal Cleavage Crack deflection Energy dissipation