A mechanism for Frenkel defect creation in amorphous SiO₂facilitated 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)-SiO. The precursor sites composed of wide O-Si-O bond angles in amorphous SiO 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 [Formula: see text] interstitial ions characterized by low transition barriers. The low barriers for the migration of [Formula: see text] 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-SiO based electronic and memory devices.

A microscopic mechanism of dielectric breakdown in SiO2 films: An insight from multi-scale modeling

“…38 This mechanism stems from the recent discovery that extra electrons can be trapped in the a-SiO 2 network and form deep electron states in the band gap of a-SiO 2 . 36 These trapping sites correspond to wide O-Si-O angles (>132 ) in the otherwise continuum random network a-SiO 2 structure and can accommodate up to two electrons.…”

“…As a result, the energy barrier to break the Si-O bonds adjacent to the trapped bi-electron is lowered to around 0.7 eV on average. 38 The detailed description of these electron traps, their optical absorption and EPR signatures, and electron injectioninduced bond dissociation in a-SiO 2 can be found in Refs. 36 and 38.…”

“…It turns out that when such wide angle intrinsic sites trap two electrons, the Si-O bond dissociation activation energy is reduced significantly, which facilitates the formation of O vacancies and interstitial O ions. 38 These studies suggest that both pre-existing defects and charge trapping play an active role in a-SiO 2 film and MOSFET degradation.…”

Light-activated resistance switching in SiOx RRAM devices

“…Electron injection and trapping at intrinsic defects in the pristine oxide lead to the increase in the creation rate of Frenkel pairs, which consist of oxygen vacancies and oxygen interstitial ions, with oxygen interstitial ions having low migration barriers (around 0.2 eV). 9,22 This results in faster conductive filament production by promoting oxygen vacancy formation. Once sufficient vacancies have been generated to create a continuous or semi-continuous filament bridging the oxide, the device switches to the LRS.…”

“…A crucial first step in this process is the generation of mobile oxygen species which, in the case of silicon oxide, is thought to involve a combination of applied field and electron injection. 9,10 There have been a handful of studies on light controllable resistance switching, [11][12][13][14] which conclude that optical illumination can improve switching properties or be an enabler for resistance switching. In these studies, the light illumination was used to control the resistance by modulating the trapped electrons in the binary strucutres 11 or by modulating the Schottky-like barriers.…”