Programme

P.86 -- Posters, VCTP-51

Date: Thursday, 6 August 2026

Time: 09:30 - 10:30

Design of polaron confinement by Ta doping in rutile TiO$_2$ for colossal permittivity

Ngoc Dung Dinh (1, 2), Van An Dinh (1), Quang Minh Ngo (2), and Yoshitada Morikawa (1)

(1) Department of Precision Engineering, Graduate School of Engineering, the University of Osaka, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan; (2) Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Nghia Do, Hanoi, Vietnam

Polarons in Nb-doped TiO$_2$ have attracted significant interest due to their hopping behavior, which contributes to the colossal permittivity observed at low temperatures. However, polaron hopping and its impact on permittivity of TiO$_2$ doped with other pentavalent elements has not yet been systematically investigated. In this work, we employ density functional theory (DFT), combined with chemical bond analysis, to investigate the behavior of polarons in Ta-doped TiO$_2$, and their influence on the permittivity. We find that the polaron in Ta-doped TiO$_2$ preferentially localizes at the second-nearest Ti site relative to the Ta dopant along the [001] direction. This behavior contrasts with that of V- and Nb-doped TiO$_2$, where the polaron is most stable at the dopant site and the first-nearest Ti neighbor of the dopant, respectively. The polaron in Ta-doped TiO$_2$ predominantly hops between Ti sites located between Ta dopants, rather than passing through the dopant itself, in contrast to Nb-doped TiO$_2$. This behavior suggests a higher permittivity in Ta-doped TiO$_2$ at low temperatures. At high doping concentrations, we also find that Ta dopants exhibit a tendency to stay spatially separated rather than forming a cluster. This arrangement is expected to promote extended polaron hopping pathways, thereby contributing to an increase in permittivity.

Presenter: Dinh Ngoc Dung