Strain states and evolutionary mechanism of microstructures at the crack tips of monocrystalline silicon

Strains, microstructures and dislocations at crack tips on silicon were studied using EBSD and TEM. Anisotropic strain distributions existed in the cracking regions on Si (001) and Si (111). Strain concentration zones at the crack tips were generated on both Si (001) and Si (1 1 1). The area of strain concentration zone on Si (1 1 1) was larger than that on Si (001). Positive and negative strains with extremums of & PLUSMN;5% were generated due to the dislocations with Burger's vector of a/2 (110). Dislocation generation was the root cause of plastic deformation and strain concentration at the crack tips. Further crack propagation was inhibited by the strain concentration zone and the material resistance from the outer thin foil into the thicker regions of the foil. Although tau max of 3.09 GPa along (220) was bigger than tau f110 of 1.01 GPa, tau max was smaller than Kg of 3.34 GPa and Kc of 25.01 GPa. That was the reason why strain states at the crack tip existed stably. Kc was bigger than Kg, which revealed that dislocation generation preceded crack propagation at the crack tip. Dislocation movement and microcrack nucleation-propagation were coexisting but competing, which was the evolutionary mechanism of quasi -cleavage fracture of monocrystalline silicon.

Automated summary

This study investigates strains, microstructures, and dislocations at crack tips on silicon. Anisotropic strain distributions and strain concentration zones were observed at crack tips on different crystal planes. The generation of dislocations was found to be the main cause of plastic deformation and strain concentration. The presence of strain concentration zones and material resistance inhibited further crack propagation.