STM and X-Ray Diffraction Temperature-Dependent Growth Study of SrRuO3 PLD Thin Films

SrRuO3 (SRO) has recently found a number of applications in different fields, e. g. as a buffer layer for the growth of high temperature superconductor (HTS) YBa2Cu3O7-x films and as a bottom electrode for ferroelectric or high dielectric constant thin film capacitors and nonvolatile data storage. The growth of high crystallinity SRO films with good structural and electrical properties is the prerequisite for each of these applications. In this paper we describe the affect of one growth parameter, temperature (T), on the crystalline quality, epitaxial substrate relationship and resulting electrical properties. SRO films were deposited on LaAlO3 single crystal substrates by pulsed laser deposition at substrate temperatures (Ts) ranging from room temperature (RT) up to 800° C with a nominal film thickness of 150 nm range. The resulting films were characterized by x-ray diffraction, 4-point transport, and STM. The films’ microstructures, as revealed by STM, evolved from polygranular at RT to a layered plate-like structure at higher deposition temperatures, Ts. Increasing Ts was marked first by increasing grain size, then a stronger orientational relationship between film and substrate, finally followed by the development of increased connectivity between grains to an extended island or condensed layered state. The transition from polygranular to layered structure occurred at Ts > 650° C. Increased conductivity paralleled the changes in microstructure. The surfaces of all of the films were relatively smooth; the oriented films are suitable for use as conductive templates in multilayer structures.