Thin film deposition: a novel synthetic route to new materials

In this paper, we discuss the utility of thin film deposition as a synthetic approach to the realization of new oxide materials. Thin film deposition has been shown previously to be well suited to stabilizing both highly metastable phases and superlattices having unique atomic order which are not attainable via classical preparatory routes. That this approach is only in the early stages of realizing its full potential as a synthetic method is demonstrated using classical pulsed laser deposition to grow new, artificially layered materials. Superlattices of metastable copper and manganese oxides having perovskite-like sub-cells were grown; they have the nominal formulae (La _0.8 Ba _0.2 CuO _2.6±x ) _m (SrCuO _2+δ ) _n and (LaMnO ₃ ) _m (A′MnO ₃ ) _n (A′=Sr and Y). Superlattice reflections are observed in the X-ray diffraction spectra, indicative of a two-dimensional cationic order not observed in bulk materials of similar stoichiometries. Moreover, the chemistry of the dimensionally confined layers in the superlattices differs from that of similar ‘bulk-like’ materials. Anomalous CMR effects are presented for the (LaMnO ₃ ) _m (SrMnO ₃ ) _n superlattices, demonstrating that new and unique physical properties are attainable via this particular synthetic approach. We also discuss the structure and growth mode of single films of LaMnO ₃ with respect to superlattice formation.