Lead-Free Layered Perovskite Film Capacitor for Ferroelectric Random Access Memory

摘要

Lead-free Bi_(3.15)Sm_(0.85)Ti_3O_(12) (BSmT) thin films were grown on Pt/TiO_2/SiO_2/Si(100) substrates using the method of metal-organic sol decomposition. The BSmT film capacitor with a top Pt electrode showed significantly improved values of the remanent polarization (2Pr) and the nonvolatile charge as compared to those of the Bi_(4-x)La_xTi_3O_(12) (BLT; x=0.75) film capacitor, recently known as the most promising candidate for nonvolatile memories. 2P_r value of the BSmT capacitor was 52 藽/cm~2 at an applied voltage of 12 V while the net nonvolatile switching charge was as high as 20 μC/cm~2 and remained essentially constant up to 4.5x10~(10) read/write switching cycles at a frequency of 1 MHz. In addition to these, the capacitor demonstrated excellent charge-retention characteristics with its sensing margin of 17 μC/cm~2 and a strong resistance against the imprinting failure.