A mechanism for Frenkel defect creation in amorphous SiO2 facilitated by electron injection

Abstract

Using density functional theory (DFT) calculations we demonstrate how electron injection can facilitate the creation of Frenkel defects in amorphous (a)-SiO2. The precursor sites composed of wide O–Si–O bond angles in amorphous SiO2 act as deep electron traps and can accommodate up to two extra electrons. Trapping of two electrons at these intrinsic sites results in weakening of a Si–O bond and creates an efficient bond breaking pathway for producing neutral O vacancies and interstitial ions characterized by low transition barriers. The low barriers for the migration of ions of about 0.2 eV facilitate the separation of created defects. This mechanism may have important implications for our understanding of dielectric breakdown and resistance switching in a-SiO2 based electronic and memory devices.