Authors: Y. Umeno and T. Kitamura
Affilation: Kyoto University, Japan
Pages: 415 - 418
Keywords: ab initio, silicon, idal strength, shear deformation, inner displacement, band gap
Single crystal of silicon is commonly used for the substrate of electronic devices. Large stress is induced in the substrate due to thermal mismatch of device component. It is well known that a defect such as dislocation brought about by the stress aggravates the electronic property of silicon. It has been reported that the ideal shear strength can be correlated to the resolved shear stress to introduce the dislocation in the substrate. In this study, in order to evaluate the ideal shear strength, homogeneous shear deformation of silicon single crystal (slip plane: (111), slip direction: [ 01])is simulated by the ab initio calculation based on plane waves. Especially, the focus is put on the effects of normal stress and the inner displacement of atoms in the cell under the shear strain. The normal stress strongly affects on the instability strain, and the inner displacement remarkably decreases the strength. The peak stress of silicon crystal is about 10GPa at the shear strain of 0.3. The band gap becomes narrow as the strain increases. Since it disappears at the shear strain of 0.2, the deterioration of electronic property is more sensitive to the shear deformation than the mechanical one.