Device physics of ferroelectric thin-film memories

Band structure match-ups are given theoretically from X-ray photoemission s pectroscopy (XPS) for the electrode interfaces between platinum electrodes and the ferroelectric thin-film materials commonly used for random access m emories(DRAMs and nonvolatile FRAMs): strontium bismuth tantalate(SBT), bar ium strontium titanate (BST), and lead zirconate titanate (PZT). The result s all agree with experimentally measured Schottky barrier heights. The elec tronegativity constant or S-factor (derivative of Schottky barrier height w ith respect to electron affinity) is found to be approximately 0.7 for thes e materials, not the purely ionic value of 1.0. The reduction of a factor o f a million in the effective Richardson coefficient is explained. And the p aradox of avalanche breakdown but decreasing breakdown fields with increasi ng temperature is reconciled.