Electronic and Dielectric Properties of Epitaxial CaSnO₃ Films

The alkaline-earth stannate CaSnO₃ has recently emerged as a promising ultra-wide bandgap perovskite oxide owing to its wide bandgap (4.4 - 4.6 eV) and structural compatibility with other functional oxides. We successfully synthesized epitaxial CaSnO₃ films using hybrid molecular beam epitaxy and systematically investigated their transport properties by doping with La [1]. A metal-insulator-metal capacitor based on CaSnO₃ exhibited a stable dielectric constant of ~15-20 and a low loss tangent (< 0.04) over wide ranges of temperature (1.8 - 400 K) and frequency (20 Hz - 1 MHz), independent of thickness or electrode geometry. Additionally, hard X-ray photoelectron spectroscopy revealed a conduction band offset of ~ 0.5 eV relative to SrTiO₃, suggesting potential viability of modulation doped heterostructures consisting of CaSnO₃ and SrTiO₃.

[1] F. Liu, P. Golani, T. K. Truttmann, I. Evangelista, M. A. Smeaton, D. Bugallo, J. Wen, A. K. Manjeshwar, S. J. May, L. F. Kourkoutis, A. Janotti, S. J. Koester, B. Jalan, ACS Nano 2023, 17, 17, 16912–16922