Microstructure of Epitaxial SrTiO₃/Pt/Ti/ Sapphire Heterostructures

Abstract

The microstructure and orientation relationships of epitaxial (111)-oriented SrTiO3 thin films grown by radio frequency magnetron sputtering on epitaxial (111)-oriented Pt/Ti electrodes on sapphire were investigated using x-ray diffraction, conventional and scanning transmission electron microscopy. We show that the epitaxial growth of (111)-oriented SrTiO3 films was promoted by thin Ti adhesion layers underneath the Pt electrode. The SrTiO3 films nucleated with two twin-related orientation variants, rotated by 180° about the 〈111〉 surface normal. The twin boundaries were oriented approximately normal to the film plane, but no strong preference for a specific boundary plane was observed. Growth mechanisms and the relationships to the dielectric properties are discussed.

Contributions to the dielectric losses of textured SrTiO3 thin films with Pt electrodes

“…Some (100) oriented grains could also be detected in XRD. In contrast, the SrTiO 3 films grown on the electron beam evaporated Pt with Ti adhesion layers contained mostly (111) oriented grains, as was confirmed by plan-view TEM studies that will be reported elsewhere [16]. The (111) peaks of SrTiO 3 in the XRD spectra ( Fig.…”

“…Substrates for the electron beam evaporated Pt electrodes were covered with ~ 3 nm thick e-beam Ti adhesion layers, which significantly affected the texture of the SrTiO 3 films subsequently grown onto them, as described below. As reported elsewhere [14][15][16] . The epitaxial Pt films showed rotational twinning [14,15,17].…”

Atomic structure of (111) SrTiO3∕Pt interfaces

“…Despite their technological importance, relatively few studies have succeeded in obtaining an atomic level understanding of these interfaces. Pt/SrTiO 3 thin film heterostructures are an ideal model system [10][11][12][13]. SrTiO 3 is an incipient ferroelectric with the cubic perovskite structure and it has a small lattice mismatch with Pt (~ 0.4 % at room temperature).…”

“…SrTiO 3 is an incipient ferroelectric with the cubic perovskite structure and it has a small lattice mismatch with Pt (~ 0.4 % at room temperature). We have recently shown that (111) SrTiO 3 thin films can be grown epitaxially on (111) oriented epitaxial Pt electrodes on (0001) sapphire if a thin (~ 3 nm) Ti layer was deposited under the Pt electrode [13]. If no Ti layer was present, the SrTiO 3 thin films were predominantly (110) oriented, although they also showed an epitaxial relationship with the (111) Pt electrode [12].…”

“…This wafer had been exposed to a 5 min "pre-sputtering" treatment in the and small letters represent Sr-O or Ti layers, respectively. In the film interior twin boundaries were oriented mostly perpendicular to the film surface, but did not show pronounced faceting [13]. Films grew in an island (Volmer-Weber) growth mode, with threading dislocations accommodating small misorientations between the nuclei upon coalescence [13].…”