NEW OR METASTABLE PHASES GROWN BY PLD
Jacques PERRIERE, Groupe de Physique des Solides, Universités Paris VI, Campus
Boucicaut, 140 rue de Lourmel, 75015 Paris, France.
Pulsed-laser deposition (PLD) is routinely used to obtain thin films, superlattices or
heterostructures. Besides this classical aspect, PLD may be now used for growing thin films with
new or metastable phases. Firstly, by the combinatorial approach it is possible to explore new
compositions or continuously spread compositions in thin films. Moreover due to the
stabilisation effect of phase by epitaxy on a substrate, the solubility limits of dopants in epitaxial
films can differ significantly from bulk values, leading to new compounds with new functional
properties. This approach will be discussed in the case of ZnO related compounds, taking into
account an important limitation related to the size and valency of the doping element. Secondly,
the growth of oxide films by PLD needs a partial oxygen pressure. It is therefore possible to
control the oxygen incorporation and therefore the stoichiometry of the oxide films, leading to
the growth of oxygen deficient metastable phases which can not be obtained in bulk form. This
aspect will be presented in the particular case of Ti-based perovskites, for which the Ti4+ as well
as Ti3+ ions can be stabilised according to the oxygen pressure during the growth. As a matter of
fact, epitaxial SrTiO2.5 thin films grown on MgO single crystal substrates under high vacuum,
show a high electronic conductivity, very different from the insulating behaviour observed in
stoichiometric SrTiO3 films. The effect of growth conditions on the structure and microstructure
of the films will be presented and correlated to their properties, and potential applications of such
metastable phases will be discussed.