Low Temperature Heteroepitaxial Growth of a New Phase Lead Zirconate Titanate Film on Si Substrate with an Epitaxial (ZrO_2)_<1-x>(Y_2O_3)_x Buffer Layer

We investigated the crystalline and electrical properties of heteroepitaxial lead zirconate titanate (PZT) films grown on Si covered with epitaxial (100) (ZrO_2)_<1-x>(Y_2O_3)_x (YSZ) buffer layers. The PZT films were prepared by reactive sputtering. When the substrate temperature was between 400 and 485°C, we obtained a heteroepitaxial (110) oriented monoclinic PZT (m-PZT) film which was metastable. The lattice parameters were as follows: a=b=0.379 nm, c= 0.521 nm and γ=81.3°. The m-PZT film had a larger oxygen composition ratio O/(Zr+Ti) of 3.2 to 3.8 than the perovskite phase. Although the resistivity of the as-grown m-PZT film was much lower than that of the normal perovskite phase, it was increased by two to five orders of magnitude by a step-annealing process of 300°C for 120 min, 325°C for 120 min and 350°C for 180 min in sequence. From the C?V characteristics of the step-annealed m-PZT/YSZ/Si structure, the relative dielectric constant was estimated to be about 45.