TITLE: From point defects to the extended structure in Si

SPEAKER: Yaojun Du,

TIME: Monday June 13, 2005 at 4 PM

PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

Molecular dynamics combined with the nudged elastic band method reveals the microscopic self-diffusion process of compact silicon tri-interstitials. During the diffusion, a five defect-atom entity both translates and rotates in a screw-like motion along <111> directions with a diffusion barrier of 0.5 eV. The low-diffusion barrier suggests that the compact tri-interstitial is highly mobile and may play an important role in the growth of ion-implantation-induced extended interstitial defects. The combination of tight-binding molecular dynamics and density functional theory reveals a possible growth mechanism of silicon interstitial chains from the compact silicon tri-interstitial. We estimate the transition rate from a compact tri-interstitial to ground state tri-interstitial is 7.8 exp(- 1.4/k_BT) THz. The ground state tri-interstitial cannot directly develop into a short interstitial I₃-chain, which can readily decay to a ground state tri-interstitial with a barrier of ~ 100 meV. On the other hand, the ground state tri-interstitial can develop into a I₄-chain with a strong exothermic reaction by capture of a single interstitial, which starts the growth process of a interstitial chain.

100 Olin Physical Laboratory, 7507 Reynolda Station Wake Forest University Winston-Salem, NC 27109-7507 Phone: (336) 758-5337, FAX: (336) 758-6142 E-mail: wfuphys@wfu.edu	Quick Links Academics Research People Colloquia Info Physics