Growth of highly oriented La 0.84 Sr 0.16 MnO 3 perovskite films

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We have grown thin films of La0.8&~.~~Mn03 on SrTiO3 (loo), MgO (loo), Ce02 (100)/A1203, and (100) oriented yttria-stabilized zirconia (YSZ) substrates by using a 90" off-axis RF magnetron sputtering deposition. X-ray diffraction analysis and ion beam channeling experiments reveal that the deposited films grow epitaxially on SrTi03, biaxially textured on MgO, and highly textured on YSZ. Scanning tunneling microscopy reveals that the thin films possess extremely smooth surfaces.

1. INTRODUCTION

Research into the growth of high-quality single crystalline thin films of high T , superconductors has stimulated interest in other, similar, perovskite metal oxides with a variety of physical properties.' Thin films of perovskite materials are potential candidates for electrochemical, magnetic, catalytic, gas separation, sensor, optical, and superconducting applications, For example, perovskite-type solid solutions based on lanthanum strontium manganate of composition Lao84Sro 16MnO3 have been reported to be the most promising high temperature fuel cell electrodes because of their good chemical and thermal compatibility with yttriastabilized zirconia (YSZ) and their high catalytic activity for the reduction of oxygen.2 Unfortunately, 16MnOs have been largely single crystals of Lao unavailable as a model catalyst/electrolyte system. In addition, recently the discovery of colossal magnetoresistance (CMR) effects in lanthanum strontium manganates3 offers possibilities for improved magnetic sensors and memories. Growth of highly oriented thin films of lanthanum strontium manganates may optimize CMR properties, thus improving magnetic devices. Lao s4Sro16Mn03is also desirable as normalmetal oxide electrodes in epitaxial, multilayer electronic, and magnetic film devices. In our work, we report the structural properties of the thin films of oriented and highly textured lanthanum strontium manganate of composition Laos4Sro16Mn03 grown on different substrates commonly used for electrochemical, electronic, and magnetic device fabrications.

II. EXPERIMENTAL We have deposited in situ films using 90" off-axis radio-frequency (RF) magnetron ~ p u t t e r i n g ~from ,~ a single 2-inch-diameter, hot-pressed stoichiometric target of Lao.&ro 16Mn03 (purchased from Seattle Specialty Ceramics) onto SrTiO3 (loo), MgO (loo), and 2518

J. Mater. Res., Vol. 10, No. 10, Oct 1995

http://journals.cambridge.org

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yttria stabilized zirconia (YSZ) (100)-oriented substrates and onto (100) oriented films of Ce02 grown on rplane sapphire.6 The substrates were fastened using silver paint, to a resistively heated nickel plate, and the temperature was measured using an IR pyrometer. All of the depositions were carried out at an RF power of 100 W and a growth temperature of 700 "C. Typical sputtering pressures were between 40 and 42 mTorr (60% argon and 40% oxygen). After deposition, the films were cooled down in pure oxygen, at a pressure of 5 Torr. X-ray diffraction methods were used to characterize the crystal structure, quality,

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