Heterostructures for Programmable Catalysis

Realizing capacitors with high capacitance (>1.5mF/cm²), and low leakage current density (<1e^-6 A/cm²) with the ability to modulate high charge density (>2e¹³/cm²) are essential for various device applications. Recent studies have shown that programmed modulation of devices with high density of charges on catalyst surfaces can also allow for direct control over the surface chemistry and accelerate the reaction rates [1]. Perovskite oxide thin films with high dielectric constants (k) such as SrTiO₃ (k~300) and BaTiO₃ (k~600)  are ideal candidates for use in these applications for programmable catalysis [2]. In this work, we address the challenge of maintaining high capacitance per unit area while reducing the leakage by interfacial engineering. We report epitaxial growth of SrTiO₃-CaSnO­₃ heterostructure on Nb:SrTiO₃ (001) substrate via hybrid MBE approach. Thin CaSnO₃ film is introduced as a wide band gap (~4.6eV) layer to engineer the interface for obtaining low leakage. Pt/SrTiO₃-CaSnO­₃/Nb:SrTiO₃ capacitors were fabricated exhibiting high room-temperature capacitance ~1.8 mF/cm² at a leakage current density of 2e^-7 A/cm²_. We will present a detailed growth study, structural characterization, and electrical properties for various thicknesses of the SrTiO₃-CaSnO­₃ stack.

References

[1]          T. M. Onn et al., Platinum Graphene Catalytic Condenser for Millisecond Programmable Metal Surfaces, J. Am. Chem. Soc. 144, 22113 (2022).

[2]          Z. Yang, D. Lee, J. Yue, J. Gabel, T.-L. Lee, R. D. James, S. A. Chambers, and B. Jalan, Epitaxial SrTiO₃ Films with Dielectric Constants Exceeding 25,000, Proceedings of the National Academy of Sciences 119, e2202189119 (2022).