Surface step terrace tuned microstructures and dielectric properties of highly epitaxial CaCu3Ti4O12 thin films on vicinal LaAlO3 substrates

Abstract

Controllable interfacial strain can manipulate the physical properties of epitaxial films and help understand the physical nature of the correlation between the properties and the atomic microstructures. By using a proper design of vicinal single-crystal substrate, the interface strain in epitaxial thin films can be well controlled by adjusting the miscut angle via a surface-step-terrace matching growth mode. Here, we demonstrate that LaAlO3 (LAO) substrates with various miscut angles of 1.0°, 2.75°, and 5.0° were used to tune the dielectric properties of epitaxial CaCu3Ti4O12 (CCTO) thin films. A model of coexistent compressive and tensile strained domains is proposed to understand the epitaxial nature. Our findings on the self-tuning of the compressive and tensile strained domain ratio along the interface depending on the miscut angle and the stress relaxation mechanism under this growth mode will open a new avenue to achieve CCTO films with high dielectric constant and low dielectric loss, which is critical for the design and integration of advanced heterostructures for high performance capacitance device applications.

Contact Guidance Effect and Prevention of Microfouling on a Beta Titanium Alloy Surface Structured by Electron-Beam Technology

“…As expected, surface texturing increases roughness with respect to the mirror polished samples because of the introduction of the grooves. However, as previously reported for Ti-cp and Ti6Al4V, the final roughness value of the treated samples is lower (or slightly higher, in the case of EB10HT) than the threshold reported in the literature to avoid an increase in bacterial adhesion (0.2 µm) [48][49][50]. The Ra values here obtained on Ti15Mo samples are close to the ones obtained on Ti-cp and Ti6Al4V [32,33].…”

Controlled BZO Nanorod Growth and Improved Flux Pinning in YBCO Films Grown on Vicinal STO Substrates

“…The vicinally grown YBCO films exhibit a range of unique phenomena, including lattice misfit-induced defect modifications, , anisotropic critical current density, , twin domain modifications, vortex channeling, and c -axis tilt alterations due to the combined strain from lattice misfit and surface-step dimensions . Moreover, the interfacial and surface effects at the substrate/film interface can significantly alter the alignment and uniformity of the second-phase nanorod inclusions in the YBCO films, providing a tool to fine-tune the vortex pinning landscape for specific applications. , It has been found that the superconducting properties are influenced by both lattice misfit strain and surface-step dimensions, where the formation of the nanocolumns further helps to accommodate the strain and to reduce the defect density in the YBCO matrix. , To gain a comprehensive understanding of the substrate surface’s impact on the critical characteristics of YBCO film with regard to the APC concentration, a more systematic investigation of the growth mechanism is necessary.…”

Breaking Lattice Symmetry in Highly Strained Epitaxial VO2 Films on Faceted Nanosurface

“…In fact, surface step terraces (SSTs) are present on the r-planes (Figure b). Chen et al developed a model for inducing local strain by lattice mismatch on step terraces that may explain the origin of the strain in SL-N. − In theory, the local strain ε induced by SSTs can be calculated as follows , where Δ d is the residual space, D is the width of the terrace, N f is the maximum number of film unit cells on one terrace to ensure positive Δ d , a f is the lattice constant of the bulk film, and a f ’ is the resultant unit-cell spacing in the film. Equation is for elongated conditions, and eq is for the compressed case.…”