Abstract
Using density functional theory (DFT) calculations, we investigated oxygen vacancy diffusion and aggregation in relation to dielectric breakdown in amorphous silicon dioxide (a-SiO2). Our calculations indicate the existence of favourable sites for the formation of vacancy dimers and trimers in the amorphous network with maximum binding energies of approximately 0.13 eV and 0.18 eV, respectively. However, an average energy barrier height for neutral vacancy diffusion is found to be about 4.6 eV, rendering this process unfeasible. At Fermi level positions above 6.4 eV with respect to the top of the valence band, oxygen vacancies can trap up to two extra electrons. Average barriers for the diffusion of negative and double negatively charged vacancies are found to be 2.7 eV and 2.0 eV, respectively. These barriers are higher than or comparable to thermal ionization energies of extra electrons from oxygen vacancies into the conduction band of a-SiO2. In addition, we discuss the competing pathways for electron trapping in oxygen deficient a-SiO2 caused by the existence of intrinsic electron traps and oxygen vacancies. These results provide new insights into the role of oxygen vacancies in degradation and dielectric breakdown in amorphous silicon oxides.
Highlights
IntroductionThe fundamental mechanisms behind these processes are still poorly understood
The aggregation of oxygen vacancies as a result of electrically stressing amorphous SiOx (x = 1.3–2) films is thought to facilitate the dielectric breakdown of complementarymetal-oxide-semiconductor (CMOS) devices [1] and electroforming in resistive random access memory devices (RRAM) [2,3,4,5,6]
Feasibility of the latter process and use theoretical modelling to investigate the structures and binding energies of vacancy dimers and trimers in a-SiO2, energy barriers for individual vacancy diffusion, and whether this diffusion can be stimulated by the trapping of injected electrons at vacancies
Summary
The fundamental mechanisms behind these processes are still poorly understood. Both the creation of additional oxygen vacancies [3, 6, 7] and the clustering of diffusing vacancies [2, 5] have been proposed as mechanisms for vacancy aggregation. The aggregation of oxygen vacancies has been suggested as the mechanism for electroforming and resistive switching in RRAM devices employing several oxides, such as TiO2 and NiO, as reviewed in [8]. The resistive switching mechanism of Ti/HfOx/Pt memory devices, studied using x-ray photoelectron spectroscopy and cross-sectional transmission electron
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
