Compensated thermal conductivity of metallically conductive Ta-doped TiO2

Abstract

Electrical and thermal conductivities of epitaxial, high-quality Ta-doped TiO2 (Ta:TiO2) thin films were experimentally investigated in the temperature range of 35–375 K. Structurally identified as the anatase phase, degenerate Ta doping leads to high electrical conductivity in TiO2, reaching >105 (Ω-m)−1 at 5 at. % of Ta, making it a potential candidate for indium-free transparent conducting oxides. In stark contrast, Ta doping suppresses the thermal conductivity of TiO2 via strong phonon-impurity scattering imposed by the Ta dopant which has a high mass contrast with Ti that it substitutes. For instance, the near-peak value shows a >50% reduction, from 9.0 down to 4.4 W/m-K, at just 2 at. % doping at 100 K. Interestingly, further Ta doping beyond 2 at. % no longer reduces the measured total thermal conductivity, which is attributed to a high electronic contribution to thermal conduction that compensates the alloy-scattering loss, as well as possibly the renormalization of phonon dispersion relation in the heavy doping regime originating from doping-induced lattice stiffening. As a result, at high Ta doping, TiO2 exhibits high electrical conductivity without much degradation of thermal conductivity. For example, near room temperature, 5 at. % Ta doped TiO2 shows over 3 orders of magnitude enhancement in electrical conductivity from undoped TiO2, but with only less than 10% reduction in thermal conductivity. The metallic Ta:TiO2 maintaining reasonable good thermal conductivity might find application in energy devices where good conduction to both charge and heat is needed.

Electronic structure and effective mass analysis of doped TiO$_2$ (anatase) systems using DFT+$U$

“…The band gap was essentially unchanged, which could mean that Tadoped TiO 2 to have transparency similar to that of pristine TiO 2 . Improved conductivity in Ta-doped anatase thin films has also been observed experimentally [41,42,6,43]. Nb dopant formed delocalized Nb states (see Fig.…”

Anisotropic thermal conductivity in two-dimensional van der Waals crystals

“…크로 패드에서의 온도 상승, 그리고 sensing 마이크로 패드에서의 온도 상승을 나타낸다. [37] 최종적으로 물질 의 열전도도는 κ=LG s /A 식에 의해서 구할 수 있으며, 여기서 L과 A는 물질의 길이, 그리고 단면적이다. [38] TMB는 MWNTs [39] 뿐만 아니라, 그래핀, [52,58] 질화 붕 소, [40] 흑린, [31] 그리고 TMDs [59] 전 소자에서 뛰어난 가능성을 보여주었다.…”

Ta Doping Effect on Structural and Optical Properties of InTe Thin Films

“…For instance, several Ti-doped chalcogenides have been well studied in theory and experiments, but little has been reported about other inert metal elements [ 15 , 19 ]. In the present work, tantalum, an inert metal element, is chosen as the dopant because it has a higher solid solubility and can induce high electrical conductivity while preserving high transmittance [ 20 , 21 ]. For example, Ta has been used as an outstanding candidate for improving stability and thermal properties of chalcogenide thin films [ 22 ].…”