This letter presents the formation of nickel nanocrystal on HfO2 high-k dielectric and its application to the nonvolatile memory devices. The effects of the initial nickel layer thickness and annealing temperature on nickel nanocrystal formation are investigated. The n-metal-oxide-semiconductor field-effect transistor with nickel nanocrystals and HfO2 tunneling dielectrics is fabricated and its programming, data retention, and endurance properties are characterized to demonstrate its advantages for nonvolatile memory device applications.

A simple preparation process of Na-4-mica (ideal brittle mica composition of Na4Mg6Al4Si4O20F4‚xH2O) from kaolinite yielded a nearly pure and very fine Na-4-mica with a crystallite size of about 0.2 µm. Strontium-sodium ion exchange in the hydrated interlayers of the Na-4-mica was demonstrated with this fine mica. The forward ion exchange of Sr 2+ f 2Na + (Sr-ion adsorption) was determined after equilibration for 4 weeks, and the Sr exchange capacity reached a value of about 200 mequiv (100 g) -1 . The parabolic diffusion or modified Freundlich model described the forward exchange process well. Only a small reverse exchange 2Na + f Sr 2+ (Sr-ion desorption) occurred from the hydrated Sr 2+ -saturated sample in 4 weeks. The irreversible sodium-strontium ion-exchange isotherm was obtained at room temperature after 4 weeks of equilibration. This mica showed much higher selectivities for Sr and Ba than for Mg and Ca, as expected. This selective Sr-ion exchanger with a large ion-exchange capacity and extremely low Sr leachability is expected to be useful for 90 Sr removal followed by its immobilization at room temperature.

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The relationship between the structural property and the electrical characteristics of thin Si02 below 4nm is investigated. The structural "strained-layer" near SiOz/Si interface is confirmed to affect strongly the TDDB (Time Dependent Dielectric Breakdown) lifetime of the thin gate oxides. The increase of the built-in comprcssive strain analyzed by the XPS (X-ray Photoelectron Spectroscopy)-based technique is experimentally found to decrease the TDDB lifetime.

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