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Perovskite Ba0.5Sr0.5TiO3 thin films have been synthesized on (001) LaAlO3 substrates by pulsed laser ablation. Extensive x-ray diffraction, rocking curve, and pole-figure studies suggest that the films are c-axis oriented and exhibit good in-plane relationship of 〈100〉BSTO//〈100〉LAO. Rutherford backscattering spectrometry studies indicate that the epitaxial films have excellent crystalline quality with an ion beam minimum yield χmin of only 2.6%. The dielectric property measurements by the interdigital technique at 1 MHz show room-temperature values of the relative dielectric constant, εr, and loss tangent, tan δ, of 1430 and 0.007 with no bias, and 960 and 0.001 with 35 V bias, respectively. The obtained data suggest that the as-grown Ba0.5Sr0.5TiO3 films can be used for development of room-temperature tunable microwave elements.

Metallic oxide films of SrRuO 3 deposited on ͑001͒ SrTiO 3 by pulsed laser deposition have been investigated by transmission electron microscopy ͑TEM͒ techniques. These films have a single crystalline structure with an extremely smooth surface. A TEM study of cross-sectional samples shows that the film grew epitaxially on the ͑001͒ surface of the SrTiO 3 substrate. The films grew along the ͓110͔ directions with an in-plane orientation relationship of either SrRuO 3 ͓110͔//SrTiO 3 ͓100͔ and SrRuO 3 ͓001͔//SrTiO 3 ͓010͔, or SrRuO 3 ͓110͔//SrTiO 3 ͓010͔ and SrRuO 3 ͓001͔//SrTiO 3 ͓100͔. Domains with a rotation of 90°around SrRuO 3 ͓110͔ were observed in the dark-field image of plan-view samples. © 1998 American Institute of Physics. ͓S0003-6951͑98͒03308-7͔Heterostructures based on semiconductors, metals, insulators, superconductors, ferroelectrics, and metal oxides are considered as important material systems. This is because they are important in the development of device applications, as well as in fundamental issues such as in interface physics and growth mechanisms of artificial structures. 1-3 Semiconducting heterostructures have been extensively investigated over the past two decades, both theoretically and experimentally, while the study of heterostructures of metal oxides is still in the early stages of development. In the present letter, we report a transmission electron microscopy ͑TEM͒ study of the heterostructure of SrRuO 3 thin films on a SrTiO 3 substrate prepared by pulsed laser ablation.SrRuO 3 belongs to the ternary ruthenium oxide system which includes compounds such as CaRuO 3 , BaRuO 3 and Sr 2 RuO 4 . 4,5 It is a distorted, pseudo-cubic perovskite 5 and was reported to be an orthorhombic phase of GdFeO 3 type. 6 The space group was determined to be Pbnm ͑No. 62͒ and lattice parameters aϭ5. 5670, bϭ5.5304, and cϭ7.8446 Å. 7 It is paramagnetic and metallic conductive at room temperature 8 and ferromagnetic below ϳ160 K. 4 Epitaxial thin films of SrRuO 3 have been found useful for electrodes and junctions in microelectronic devices, due to the high resistance to chemical corrosion, outstanding thermal conductivity, and stability. Recently, thin crystalline films of high quality were reported to be successfully grown on different substrate materials by different methods, such as on SrTiO 3 ͑100͒ and LaAlO 3 ͑100͒ by 90°off-axis sputtering technique, 9 on LaAlO 3 ͑100͒ 10 and on SrTiO 3 ͑001͒ 11 by pulsed laser ablation. However, to our knowledge, detailed studies on the structural characteristics of these films have not yet been reported. To examine the quality of the films and to determine their crystallographic structure in order to understand their influence on physical properties, TEM investigations of both cross-sectional and plan-view specimens of the SrRuO 3 films have been conducted in the present work.SrRuO 3 thin films were deposited on ͑001͒ SrTiO 3 by means of pulsed laser ablation. Details on the growth procedure were described in the literature. 11 Cross-sectional slices were obtaine...

Perovskite barium strontium titanate Ba0.5Sr0.5TiO3(BST) thin films were grown on (001) LaAlO3 (LAO) using pulsed-laser ablation. The microstructures of the as-grown BST films were studied with selected electron diffraction, transmission electron microscopy, and scanning transmission electron microscopy. The BST thin films are oriented with their [001] directions parallel to the 〈102〉 directions of the LAO. Both cross-sectional and plan-view studies show the BST films to be single crystals with smooth surfaces. The interfaces were seen to be atomically sharp by cross-sectional, high-resolution electron microscopy. The density of misfit dislocations was consistent with the 4.3% lattice mismatch, and they were found to be dissociated into partials.

Transmission electron microscopy (TEM) of a perovskite Ba0.5Sr0.5TiO3 thin film, grown on a (001) LaAlO3 substrate by pulsed-laser ablation, reveals that the film of single-crystal quality has an unusually distorted lattice with lattice parameters a and b (parallel to the interface) larger than c (perpendicular to the interface) by 1.4%. There is evidence that the as-examined Ba0.5Sr0.5TiO3 film is a variant of its high-temperature cubic phase due to its anisotropic thermal contraction during cooling. A large lattice mismatch value of 5.7% (to be compared to the normal value of 4.13%) is observed from selected area electron diffraction patterns and high-resolution TEM images of cross-sectional specimens, which suggests that the growing high-temperature film under the film growth condition may have a larger lattice constant and a different thermal expansion behavior with respect to the bulk material.