Systematic study of homogenously oxygen-vacancy-doped bulk KTaO₃

Potassium tantalate (KTaO₃, KTO), like strontium titanate (SrTiO₃, STO), has a cubic-perovskite structure and is an incipient-ferroelectric insulator. While STO has been extensively studied across a wide range of doping levels, similar studies on KTO are much more limited. Metallicity in KTO can be achieved through electron doping, for example, by inducing oxygen vacancies. Yet, there are no reported methods to homogeneously induce oxygen vacancies in bulk KTO. Here, we report on an alternative, oxygen-getter-based annealing method to induce charge carriers in bulk KTO. We anneal KTO wafers of different surface orientations under various controlled conditions in an attempt to achieve homogeneous doping across a wide range of carrier concentrations. From Hall measurements, we have achieved higher carrier concentrations (up to 8.1×10¹⁹ cm^-3) than previous oxygen-vacancy-doping works. In addition, only 2D superconductivity has been observed in KTO (e.g., electrolyte gating) [1], so we also report on our ongoing search for bulk superconductivity in undeformed and plastically deformed KTO, motivated by a recent observation of enhanced superconductivity in plastically deformed STO [2].

[1] K. Ueno et al., Nat. Nanotech. 6, 408 (2011)

[2] S. Hameed et al., Nat Mater. 21, 54 (2022)