Lead-free layered perovskite film capacitor for ferroelectric random access memory

Abstract

Lead-free Bi3.15Sm0.85Ti3O12 (BSmT) thin films were grown on Pt/TiO2/SiO2/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 (2P(r)) and the nonvolatile charge as compared to those of the Bi4-xLaxTi3O12 (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 muC/cm(2) at an applied voltage of 12 V while the net nonvolatile switching charge was as high as 20 muC/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 muC/cm(2) and a strong resistance against the imprinting failure.