Characteristics of conductive SrRuO 3 thin films with different microstructures
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Characteristics of conductive SrRuO3 thin films with different microstructures Q. X. Jia, F. Chu, C. D. Adams, X. D. Wu, M. Hawley, J. H. Cho, A. T. Findikoglu, S. R. Foltyn, J. L. Smith, and T. E. Mitchell Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (Received 19 January 1996; accepted 20 May 1996)
Conductive SrRuO3 thin films were epitaxially grown on (100) LaAlO3 substrates by pulsed laser deposition over a temperature range from 650 ±C to 825 ±C. Well-textured films exhibiting a strong orientation relationship to the underlying substrate could be obtained at a deposition temperature as low as 450 ±C. The degree of crystallinity of the films improved with increasing deposition temperature as confirmed by x-ray diffraction, transmission electron microscopy, and scanning tunneling microscopy. Scanning electron microscopy revealed no particulates on the film surface. The resistivity of the SrRuO3 thin films was found to be a strong function of the crystallinity of the film and hence the substrate temperature during film deposition. A residual resistivity ratio (RRR r 300 Kyr 4.2 K ) of more than 8 was obtained for the SrRuO3 thin films deposited under optimized processing conditions.
I. INTRODUCTION
The metallic conductive oxide SrRuO3 , which crystallizes in the GdFeO3 -type orthorhombic distortedperovskite structure with lattice constants of a 0.5573 nm, b 0.5538 nm, and c 0.7856 nm, has recently found applications in many different fields. The thermal and chemical stability of SrRuO3 make it promising as a buffer layer for the growth of hightemperature superconducting YBa2 Cu3 O72x thin films on various substrates.1,2 The use of SrRuO3 as a normal-metal layer in the fabrication of high-temperature superconductor/normal-metal/superconductor Josephson junctions has been investigated by different groups.3,4 Its relatively high electrical conductivity and structural compatibility with ferroelectric or high dielectric constant materials also make it very attractive as a bottom electrode for dynamic random access memory capacitors.5–8 Crystalline SrRuO3 thin films have been successfully grown on different substrates, such as SrTiO3 ,9 LaAlO3 ,1,6 MgO with Pt or BaTiO3 buffer layers,2,7 and Si with yttria-stabilized zirconia (YSZ) as a buffer layer.8 The successfully employed deposition techniques have been either off-axis sputtering or pulsed laser deposition. It has been found that the resistivity of SrRuO3 is a strong function of its microstructure. Polycrystalline SrRuO3 has a room-temperature resistivity of around 1130 mV ? cm,10 whereas bulk single crystalline SrRuO3 has a room-temperature resistivity of around 280 mV ? cm.11 However, there has been no systematic study correlating structural with electrical properties of SrRuO3 thin films. J. Mater. Res., Vol. 11, No. 9, Sep 1996
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The purpose of this paper is to describe the relationship between
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