ULTRA-THIN FATIGUE-FREE BI4TI3O12 FILMS FOR NONVOLATILE FERROELECTRICMEMORIES

We have developed a new low temperature growth technique for Bi4Ti3O12 thin films using a MOCVD method in which an ultra-thin double buffer layer (5-nm thick Bi4Ti3O12/5-nm thick TiO2) is used to control the cr ystallization and fine grain structure. The 100-nm thick Bi4Ti3O12 thi n films fabricated at 400 degrees C showed an extremely smooth surface morphology and good electrical properties, namely, a large remanent p olarization of P-r = 11 mu C/cm(2), a coercive field of E(c) = 90 kV/c m and a low leakage current I-L = 7 x 10(-9) A/cm(2) at 3 V. Moreover, we successfully fabricated 50-nm ultra thin Bi4Ti3O12 films with P-r = 9 mu C/cm(2) and E(c) = 120 kV/cm at 3 V. For the first time, the fa tigue free property, which is very important for nonvolatile ferroelec tric memory (NVFRAM) applications, was confirmed up to 1 x 10(12) swit ching cycles.