Poly͑N-vinylcarbazole͒ ͑PVK͒ has been fabricated by spin-coating to show the bistable resistance switching characteristics. Various resistance states can be made by controlling the on-state current through the PVK films. The resistance of the on-state PVK films also affects the turn-off current, which needs to erase the on state. The filament theory is used to elucidate the observed phenomenon. We demonstrate that the PVK films exhibit good retention and stable "read-write-read-erase" cyclic switching characteristics. The PVK films also show a good switching behavior with on-off ratio of 10 4 , which will be a potential material for nonvolatile memory application.

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We have used composite flip chip solder joints to study thermomigration. The composite solder joint has 97Pb3Sn on the Si side and eutectic 37Pb63Sn on the substrate side. Redistribution of Sn and Pb occurs in thermomigration, and we found that Sn has moved to the Si side (the hot end) and Pb to the substrate side (the cold end). We estimate the driving force that a temperature gradient of 1000°C∕cm or a temperature difference of 10°C across a solder joint of 100μm in diameter is sufficient to induce the thermomigration.

Nanoindentation-induced mechanical deformation in GaN thin films prepared by metal-organic chemical-vapour deposition was investigated using the Berkovich diamond tip in combination with the cross-sectional transmission electron microscopy (XTEM). By using focused ion beam milling to accurately position the cross-section of the indented region, the XTEM results demonstrate that the major plastic deformation was taking place through the propagation of dislocations. The present observations are in support of attributing the pop-ins that appeared in the load–displacement curves to the massive dislocation activities occurring underneath the indenter during the loading cycle. The absence of indentation-induced new phases might have been due to the stress relaxation via the substrate and is also consistent with the fact that no discontinuity was found upon unloading.

Thermomigration in flip chip solder joints of eutectic SnPb has been studied at an ambient temperature of 100°C. Redistribution of Sn and Pb occurs with Pb moving to the cold end. A stepwise concentration profile is observed. Significantly, the lamellar microstructure becomes much finer after thermomigration. Since the lamellar interface is disordered and is a fast path of diffusion, it indicates a high rate of entropy production in the thermomigration, in agreement with Onsager’s principle of irreversible processes. The effect of entropy production on microstructure change is shown here. The molar heat of transport of Pb has been calculated to be −25.3kJ∕mole.