CMR FILMS STRUCTURE AS A FUNCTION OF GROWTH AND PROCESSING

Among the family encompassed by the complex metal oxides are the colos sal magneto-resistive perovskites with potential applications in advan ced high density magnetic data storage and sensor devices based on sin gle or multilayers of these materials fabricated by vapor phase deposi tion methods. Realization of this potential requires solving basic thi n film fabrication problems coupled to understanding the resulting str ucture-properties relationships. The specific objectives addressed in this study were to determine the dependence of growth and transport pr operties: (1) reproducibility on the pulsed laser deposition (PLD) tar get, (2) on sputter deposition chamber gas and substrate, and (3) on a post-deposition anneal in a reducing atmosphere. Toward these ends, w e have grown La0.67Ca0.33MnO3 films on perovskite substrates by PLD an d RF off-axis sputter deposition from stoichiometric targets at temper atures from 400 to 900 degrees C. The PLD films were grown from a new commercial target and post-deposition annealed in O-2 to reproduce, fo r comparison, the conditions used previously for the films grown with an in-house fabricated target. The sputter deposited films were grown in both Ar-O-2 mixed and Ar-only atmospheres, some grown simultaneousl y on different substrates; one Ar-O-2 grown film was post-annealed in a reducing atmosphere. Microstructures were studied by scanning probe microscopies and temperature-dependent transport properties by 4-point resistance measurements. Previously we reported on characterization o f the T-substrate(T-s)-dependent microstructure of PLD as-deposited an d post-annealed films consistency in T-dependent transport and magneti zation properties, independent of growth temperature. None of the as-g rown sputter deposited films grown in the Ar-O-2 mixture exhibited a m etallic transition while those grown in Ar-only at T-s > 800 degrees C had a range of transition temperatures between 110 and 180 K. The var iation in substrate-dependent structure demonstrated again the sensiti vity of growth mechanism to template. Finally, the 500 degrees C film grown in the Ar-O-2 mixture, went from insulating at all T's to exhibi ting a 215 degrees C metallic transition after the reducing anneal tre atment.