Magnetoresistant La1-xSrxMnO3 films by pulsed injection metal organic chemical vapor deposition:: effect of deposition conditions, substrate material and film thickness

High quality epitaxial La1-xSrxMnO3, films were deposited by pulsed injection metal organic chemical vapor deposition, using as precursor materials metal-2,2,6,6-tetramethyl-3,5-heptandionates dissolved in monoglyme. The influence of various deposition conditions, substrate material and film thickness on film properties was investigated. The best films were deposited on LaAlO3 substrates at 825 degreesC: films exhibited a sharp semiconductor-metal transition and high magnetoresistance (similar to40%) at a close-to-room temperature and in a rather low field of 1.5 T. In-situ or ex-situ high-temperature annealing in oxygen increased the temperature of semiconductor-metal transition, but decreased the magnetoresistance and the temperature coefficient of resistance. Biaxial strain imposed by the lattices' mismatch was clearly observed in thinner La1-xSrMnO3 films on perovskite substrates. Tensile strain was present in the films on SrTiO3, and compressive strain in the films on LaAlO3 (and less clearly on NdGaO3). Both tensile and compressive strains decreased the temperature of electric transition and the values of magnetoresistance. The strain was completely relaxed in the films more than similar to100 nm thick. (C) 2002 Elsevier Science B.V. All rights reserved.