A high-k Tb₂ TiO₅ nanocrystal memory

In this letter, a metal-oxide-high- k -oxide-silicon (MOHOS) memory structure incorporating a high-k Tb₂ TiO₅ nanocrystal film as the charge trapping layer is reported for nonvolatile memory application. The structural and morphological features of these films were explored by x-ray diffraction, transmission electron microscopic, atomic force microscopy, and x-ray photoelectron spectroscopic. The Tb₂ TiO₅ MOHOS-type memory annealed 800 °C exhibited large threshold voltage shifting (memory window of 2.9 V) and long data retention (charge loss of ∼15 % after ten years for programmed state at room temperature). These results are attributed to the higher probability for trapping the charge carrier due to the formation of a well-crystallized Tb₂ TiO₅ nanocrystal structure with a higher dielectric constant.