Influence of PZT template layer on pulsed laser deposited Pb(Mg1/3Nb2/3)O-3 thin films

Lead magnesium niobate (PMN) thin films were prepared by pulsed laser depos ition technique on different substrates. Because of the fit of the unit cel l structure and lattice constant with PMN. lead titanium zirconate (PZT) te mplate layers have been deposited on top of the bottom electrodes, while an other set of samples has been prepared by directly depositing PMN on metall ized substrates. The use of PZT layer favored the obtaining of an oriented crystalline PMN film with a minor pyrochlore content at relatively low temp erature (500 degreesC). The room temperature small-signal dielectric consta nt of the films has been measured on structures with 1 mm x 1 mm evaporated Au top electrodes, by using an impedance analyzer. The obtained values of the dielectric constant have been found to be much smaller than that of bul k PMN due to the presence of a very thin transition layer with low dielectr ic constant at the electrode/film interface, which highly decreases the eff ective dielectric constant of the samples. The measurement of the piezoelec tric properties evidenced the rather surprising presence of a relatively st rong piezoelectric effect in PMN films in the absence of a bias electric fi eld. (C) 2000 Elsevier Science B.V. All rights reserved.