Conductive Path Formation in the Ta₂O₅ Atomic Switch: First-Principles Analyses

Abstract

The conductive path formed by the interstitial Cu or oxygen vacancies in the Ta(2)O(5) atomic switch were investigated in detail by first-principles methods. The calculated results indicated that the defect state induced by the interstitial Cu is located just at the Fermi level of the Cu and Pt electrodes in the Cu/Ta(2)O(5)/Pt heterostructure and that a conduction channel is formed in the Ta(2)O(5) film via the interstitial Cu. On the other hand, oxygen vacancies in Ta(2)O(5) do not form such a conduction channel because of the lower energy positions of their defect states. The above results suggest that the conductive path could be formed by interstitial Cu in the Ta(2)O(5) atomic switch, whereas the oxygen vacancies do not contribute to the formation of the conductive path.

In situ observation of filamentary conducting channels in an asymmetric Ta2O5−x/TaO2−x bilayer structure

“…The simulation results using the first-principles method based on density functional theory [23][24][25] are shown in Fig. 1d.…”

Conduction paths in Cu/amorphous-Ta2O5/Pt atomic switch: First-principles studies

“…17 In this case, the distance between the adjacent Cu atoms, 3.91 Å , is much larger than that in the bulk Cu crystal. In addition, we found the alternate Cu-Ta bonding is essential to form a conduction path (for detail, please see supplementary material 32 ( Fig.…”

“…The computational conditions were the same as those adopted in our previous study. 17 A numerical atomic basis set, a single-f basis with polarization, was used to solve the Kohn-Sham equations. The Perdew-Burke-Ernzerhof (PBE) functional form within the generalized gradient approximation (GGA) 25 was adopted for electron-electron interaction.…”

“…In the case of the Ta 2 O 5 -based atomic switch, our study showed that a conduction channel can be formed in the crystal Ta 2 O 5 film via interstitial Cu atoms. 17 However, these our previous studies are insufficient in the sense that they assumed crystalline structures while in experimentally fabricated atomic switches have amorphous phases of oxide or electrolyte.…”

“…We focus on the Ta 2 O 5 -based atomic switch, which is particularly promising as a practical device because of its compatibility with semiconductor fabrication processes. In contrast to our previous work, 17 we examine the case of amorphous Ta 2 O 5 (a-Ta 2 O 5 ) in the present study, since the amorphous phase is usually adopted in experiments and prototype devices 18,19 as mentioned above. The atomic and electronic structures of Cu filaments of different thicknesses in a-Ta 2 O 5 have been discussed.…”