A series of micrometer-scale Si thin films were fabricated by electron-beam deposition on the Cu substrate with specially treated concave-convex surface. The combined analyses involving scanning and transmission electron microscopy, selected area electron diffraction, and X-ray diffraction revealed that the deposited Si layer possessed good adhesion to the substrate and a discontinuous amorphous microstructure in which there existed large amounts of interface regions. The surface changes of the Si thin-film electrodes during Li insertion and extraction were investigated by glow discharge optical emission spectroscopy. The half-cell tests showed that these thicker films had higher capacity and more impressive cycleability relative to those reported in the literature; their cycleability could be substantially improved by limiting Li insertion depth. The full-cell tests indicated that Si films thicker than 4 m could provide sufficient capacity to match the standard LiCoO 2 cathode with a ϳ70-m-thick coating layer. Such cells demonstrated small self-discharge rate as well as good cycling stability and efficiency in the long run, suggesting feasibility for potential practical applications.

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Three new stacking variants have been found in the systems MgZn2-MgAg 2 and MgCuz-MgA12. The crystal structure of Mg(Z%.ooAg0.~o) 2 has been determined by X-ray diffraction methods. The structure is a rhombo-

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