Control of La-doped Pb(Zr, Ti)O3 crystalline orientation and its influence on the properties of ferroelectric random access memory

We investigated the crystallization mechanisms of sputter-deposited La-doped Pb(Zr, Ti)O-3 (PLZT) on a Pt/Ti metal stack in the postdeposition annealing (PDA) at 600 degrees C in O-2-mixed Ar ambient. As-deposited amorphous PLZT generally transforms to a perovskite phase over 550 degrees C through a metastable pyrochlore phase during the PDA. We found that the O-2 content of the PDA ambient crucially affects the pyrochlore-perovskite transformation (PPT) speed. While an O-2 content much higher than 2% of the PDA ambient suppresses PPT, an O-2 content much lower than 2% enhances PPT. An O-2 content around of 2% of the PDA suppresses PPT near the surface of PLZT and simultaneously keeps PPT fast in the inner regions of PLZT in the pyrochlore phase because of the O-2 diffusion limit from the PLZT surface, eventually resulting in almost only the growth of highly {111} oriented columnar PLZT on Pt, which reveals better electric properties than those obtained by the PDA with the ambient of O-2 contents much higher or lower than 2%. (C) 2017 The Japan Society of Applied Physics