Fatigue-free Samarium-modified Bismuth Titanate Having Large Remanent Polarization and Charge-retaining Ability

Abstract

Fatigue-free and highly c-axis oriented Bi_4-xSm_xTi₃O₁₂ (BSmT; x = 0.85) 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 (P_r) and the nonvolatile charge as compared to those of the Bi_4-xLa_xTi₃O₁₂ (BLT; x = 0.75) film capacitor, recently known as a promising candidate for nonvolatile memories. The 2P_r value of the BSmT capacitor was 49 μC/cm² at an applied voltage of 10 V while the net nonvolatile charge was as high as 20 μC/cm² and remained essentially constant up to 4.5 × 10¹⁰ read/write switching cycles at a frequency of 1 MHz. In addition to these, the capacitor showed excellent charge-retention characteristics with its sensing margin of 17 μC/cm² and a strong resistance against the imprinting failure.