Device models for PZT/Pt, BST/Pt, SBT/Pt, and SBT/Bi ferroelectric memories

We have used x-ray photoelectron spectroscopy (XPS) and ultraviolet absorpt ion measurements to determine unambiguous values of the electron affinities and band structure alignments for the three most popular ferroelectric mem ory materials (strontium bismuth tantalate SET, lead zirconate-titanate PZT , and barium strontium titanate BST) on platinum electrodes. The PZT/Pt res ults and model disagree quantitatively and qualitatively with the earlier w ork of Wouters, Willems, and Maes [Microelectron. Eng. 29, 249 (1995)], who inferred an electron affinity of 2.6 eV, compared with our value of 3.5 eV . Nano-electrode fabrication is discussed for such memories, and nano-elect rode interface models of SBT/Bi are included.