Atomic structure of (111) SrTiO3∕Pt interfaces

Abstract

Atomic resolution high-angle annular dark field (HAADF) imaging in scanning transmission electron microscopy was used to investigate the interface atomic structure of epitaxial, (111) oriented SrTiO3 films on epitaxial Pt electrodes grown on (0001) sapphire. The cube-on-cube orientation relationship of SrTiO3 on Pt was promoted by the use of a Ti adhesion layer underneath the Pt electrode. While a Ti-rich Pt surface was observed before SrTiO3 growth, HAADF images showed an atomically abrupt SrTiO3∕Pt interface with no interfacial layers. The SrTiO3 films contained two twin variants that were related by a 180° rotation about the ⟨111⟩ surface normal. HAADF images showed two different interface atomic arrangements for the two twins. The role of Ti in promoting (111) epitaxy and the implications for the dielectric properties are discussed.

Growth of highly (110)- and (111)-textured SrTiO3 thin films on Pt(111)/α-Al2O3(0001) substrates by ECR ion beam sputter deposition

“…The biaxial in-plane tensile strain was mainly generated in the film due to lattice mismatch ($ 0.4%) and thermal expansion difference (a STO ¼ 10 Â 10 À 6 K À 1 and a Sap ¼7 Â 10 À 6 K À 1 ) between the film and the substrate during the growth and cooling processes, respectively [21,22]. Our finding was inconsistent with the previous reports with regard to Ti atoms penetrating the Pt(111) surface which were needed in order to promote the nucleation sites for (111)-plane formation [9][10][11][12][13]. The (111)-textured STO film on Pt(111) could be explained by two possible reasons: (i) the high growth temperature of 750 1C provided sufficient surface energy for nucleating (111)-orientation since a (111)-plane has the highest surface energy in comparison with those of (110) and (100) planes and (ii) the films grown under the low level of oxygen pressure ($ 10 -4 Torr) might prevent the formation of Ti-O bond, leading to the minimization of larger grain sizes with a triangular shape were apparently seen.…”

“…In fact, the (111)-epitaxial STO films are expected to grow on the Pt(111) electrodes due to their structural similarity and close lattice match $0.4% (a Pt ¼3.912Å, a STO ¼3.905Å), but this is very difficult to achieve with a direct growth process due to the effects of surface energy and electrostatic interaction [7,8]. In the literatures, the insertion of a thin Ti buffer layer under the Pt(111) layer played an important role to promote nucleation sites on the Pt surface for (111)-perovskite growth [9][10][11][12][13]. Without the Ti buffer layer, most previous attempts have been done on either random or preferable (100)/(110) orientations [5,[14][15][16].…”

Temperature dependence of DC voltage activated Ba<inf>0.5</inf>Sr<inf>0.5</inf>TiO<inf>3</inf> solidly mounted resonator

“…The BST layer 280nm) was deposited by radio frequency magnetron sputtering from a stoichometirc Ba 0.5 Sr 0.5 TiO 3 target. The BST deposition parameters are described in another publication [10]. The top platinum electrode was deposited by electron beam evaporation and patterned by lift-off, and annealed at 700 o C in an N 2 environment in order to obtain good contact between the BST and the top electrode.…”

Capacitively coupled dc voltage switchable barium strontium titanate solidly mounted resonator filter

“…The BST layer (280 nm) was deposited by radio frequency magnetron sputtering from a stoichometric Ba 0.5 Sr 0.5 TiO 3 target. The BST deposition parameters are described in another publication [9]. The top electrode was deposited by electron-beam evaporation and patterned by liftoff.…”