Ferroelectric and Dielectric Characteristics of (Pb_<1-y>La_y)[Mg_<(x+2y)>/3Nb_<(2x+y)>/3Ti_<1-x-y>]O_3 Thin Films Prepared by RF Magnetron Sputtering

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Ferroelectric thin films having compositions of xPb (Mg_<1/3>Nb_<2/3>)O_3+(1-x-y) PbTiO_3+yLa (Mg_<2/3>Nb_<1/3>) O_3 (PLMNT) with x=0.37-0.78 and y=0.03-0.13 were prepared on Pt/Ti/SiO_2/Si substrates by rf magnetron sputtering deposition at 520℃. Pure perovskite films were obtained for all compositions. The 0.5-μm-thick films having a constant La (Mg_<2/3>Nb_<1/3>) O_3 content of y=0.03 showed a ferroelectric-hysteresis characteristic with the remanent polarization and coercive field decreased from 8.5μC/cm^2 and 46 kV/cm to 4.2μC/cm^2 and 29 kV/cm, respectively, for changing the composition from x=0.645 to 0.78. Dielectric constant (k) of 1200-1300 and dielectric loss (tan δ) less than 0.04 were also measured at 1 kHz. The temperature of dielectric peak decreased to near room temperature for an increase of Pb (Mg_<1/3>Nb_<2/3>) O_3 content to x=0.78, which corresponded to a composition at the rhombohedral/cubic phase boundary of the PLMNT system. For films having composition lying along this phase boundary but containing La (Mg_<2/3>Nb_<1/3>) O_3⩾7 mol%, the dielectric peak became much more broadened (flattened), which provided a good dielectric stability against variation of temperature. Good dielectric stability against frequency up to 1 MHz was also observed. The films also showed weak ferroelectric-hysteresis characteristic.
社団法人応用物理学会の論文
1995-06-15