Interface engineering for substantial performance enhancement in epitaxial all-perovskite oxide capacitors

Abstract

Capacitors based on ABO3-type perovskite oxides show considerable promise for overcoming the limitations of nanoscale integration with dynamic random access memory (DRAM) devices. Among the thermodynamically stable perovskite oxides, titanates (ATiO3) exhibit high dielectric permittivity in metal–insulator–metal (MIM) configurations. However, their performance in mitigating the large leakage current caused by their narrow bandgap (3 eV) remain under scrutiny. Herein, substantially enhanced dielectric properties of an epitaxial SrRuO3/Ba0.5Sr0.5TiO3/SrRuO3 MIM capacitor with a thin dielectric layer (10 nm) are reported. The dielectric/electrode heterointerface was engineered to realize a capacitor with a low leakage current and high dielectric permittivity. A pit-free and stoichiometric SrRuO3 bottom electrode with an atomically smooth surface was exploited to suppress defect formation at the heterointerface. The critical roles of oxygen vacancies and substituted transition-metal atoms in determining the leakage current were assessed, and a strategy for reducing the leakage current via interface engineering was established. Consequently, a dielectric permittivity of 861 and a leakage current density of 5.15 × 10−6 A/cm2 at 1 V were obtained with the thinnest dielectric layer ever reported. Our work paves the way for the development of perovskite-oxide-based capacitors in next-generation DRAM memories.

Atomic‐Scale Study of Dead Layers in Epitaxial Perovskite Dielectric Thin Films with Oxide and Metal Top Electrodes

“…If Ru diffuses from the bottom SrRuO 3 electrode to the Ba 0.5 Sr 0.5 TiO 3 dielectric, the diffused Ru can form shallow‐level defects of 0.07–0.12 eV and act as a trap site for P‐F emission. [ 17 ] Both capacitors in this study demonstrated P‐F emissions with trap sites that have an energy level of 0.1 eV; thus, this P‐F emission can be attributed to Ru diffusion from the bottom electrode. Meanwhile, the dominant conduction mechanism of the capacitor with the Ru top electrode changed from the P‐F emission to the hopping conduction in the high voltage area, unlike the capacitor with the SrRuO 3 top electrode.…”

A new pathway to correlate the octahedral tilt coupling and spin-orbit reconstruction at oxide interfaces

“…The possibility for groundbreaking research lies at the interface of robust perovskite systems, where control of spin, charge, orbital, and lattice interactions holds immense possibilities from both fundamental and device perspectives. 1,2,3 To unravel the correlations among these diverse degrees of freedom, numerous approaches are being studied, including engineering of strain 4,5 , interface 6 , defects 7,8 and symmetry. 9,10 However, scant attention has been paid to the engineering of bonding geometry within and in-between metal-oxygen octahedra.…”

“…24 However, their effectiveness is constrained by the demand for high-quality interfaces. Interestingly, the unstrained perovskite LaCoO3 (LCO) is merely an insulator and non-magnetic (paramagnetic) material that exhibits a systematic temperaturedependent spin-state transition starting from a low spin state (LS, t2g 6 , S = 0) to an intermediate spin state (IS, t2g 5 eg 1 , S = 1) or a high spin state (HS, t2g 4 eg 2 , S = 2). 25,26,27 Nevertheless, the single layer LCO thin films can exhibit unusual ferromagnetic insulator (FMI) behavior with Curie temperature (TC) ranging from 24-92 K, depending on the substrate-induced strain.…”