The ferroelectric properties of c-axis oriented Pb5Ge3O11 thin films prepared by metalorganic chemical vapor deposition

Abstract

C-axis oriented ferroelectric ${\mathrm{Pb}}_{\mathrm{5}}{\mathrm{Ge}}_{\mathrm{3}}{\mathrm{O}}_{\mathrm{11}}$ thin films were prepared on Pt/Ir-coated Si wafers by metalorganic chemical vapor deposition (MOCVD) and rapid thermal process annealing techniques. The films were specular and crack free and showed complete crystallization with c-axis orientation for growth temperatures between 500 and 550 °C. Good ferroelectric properties were obtained for a 150-nm-thick film with Pt/Ir electrodes: the remanent polarization ${\text{(2P}}_r)$ and coercive field ${\text{(2E}}_c)$ values were about 3.8 μC/cm² and 93 kV/cm, respectively. The films also showed excellent fatigue characteristics: no fatigue was observed up to ${\text{1×10}}^9$ switching cycles. The leakage current increased with increasing applied voltage, and is about ${\text{3.6×10}}^{\text{−7}}\hspace{0.5em}{\mathrm{A/cm}}^{\mathrm{2}}$ at 100 kV/cm. The dielectric constant showed behavior similar to most ferroelectric materials in that the dielectric constant changed with applied voltages. The maximum dielectric constant is about 45. High-quality MOCVD ${\mathrm{Pb}}_{\mathrm{5}}{\mathrm{Ge}}_{\mathrm{3}}{\mathrm{O}}_{\mathrm{11}}$ films can be used for single transistor ferroelectric memory devices.