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In organic resistive memory device field, alternating current (AC) has seldom been studied systematically. In the present work, square wave voltage pulses are considered to obtain memory switching to the ON state with voltage amplitude lower than the threshold voltage of the device, even with less time. The ON states induced by such AC depend on both frequency and amplitude. A possible mechanism related to filamentary formation was proposed to explain the AC induced effect.

The morphologies of self-assembled Ge/Si(001) islands with initial Si capping at a temperature of 640 °C are investigated by atomic force microscopy. Before Si capping, the islands show a metastable dome shape with very good size uniformity. This dome shape changes to a pyramid shape with {103} facets at a Si capping thickness of 0.32 nm, and then changes to pyramid shapes with {104} and {105} facets at Si capping thicknesses of 0.42 and 0.64 nm, respectively. Noteworthy is that islands with one side retained their dome shape while the other three sides that changed to {103} facets are observed at a Si capping thickness of 0.18 nm. These observations indicate that island shape change with Si capping is a kinetic rather than thermodynamic process. The atomic processes associated with this island shape change are kinetically limited at a low temperature of 400 °C, and no significant change in size and shape of islands is observed when Si capping layers are deposited at this temperature.