High- κ Hf O2 nanocrystal memory capacitors prepared by phase separation of atomic-layer-deposited Hf O2 Al2 O3 nanomixtures

Physical and electrical characteristics of atomic-layer-deposited high- κ Hf O2 nanocrystals in a p-SiSi O2 [Hf O2 Al2 O3] Al2 O3 Pt at elevated temperature (∼900°C) have been investigated. Because the phase separation of high- κ Hf O2 Al2 O3 nanomixtures after high-temperature (∼900°C) treatment, the high- κ Hf O2 nanocrystals with an average diameter of 5-10 nm and moderate density of >1× 1011 cm-2 have been confirmed by both high-resolution transmission electron microscope and X-ray photoelectron spectroscope. The high- κ Hf O2 nanocrystal capacitor shows a large hysteresis memory window of ΔV≈4.2 V and high charge density of 1.1× 1013 cm2 for the sweeping gate voltage of 10 V-8 V, due to charge storage in the high- κ Hf O2 nanocrystals, while the as-deposited memory capacitor does not show memory window up to the gate voltage of 10 V. An initial memory window of ΔV≈1.2 V is observed at a small programming voltage of +5 V, and a memory window of ΔV≈0.9 V is observed after 104 s of retention at 85°C, due to the charge confinement in the layer-by-layer of high- κ Hf O2 nanocrystals.