Observation and Control of Hot Atom Damage in Ferroelectric Devices

Ferroelectric materials are the most common example of a Landau structure, defined as a system having an atom/mass moving in a double-well energy landscape. These materials have applications in memories, actuators, low power logic transistors, and so on. For a bipolar ac signal typical in most of the applications, one suspects that the repeated roller coaster shuttling of the moving atoms located microscopically at the domain walls could lead to bond dissociation, suggesting a new channel for defect generation with no classical counterpart. Here, we demonstrate that once the bipolar pulses initiate transfer of atoms between the energy pockets, the transient overshoot away from their equilibrium positions (hot atoms) leads to significant increase in defect generation. We interpret the degradation theoretically and demonstrate a set of soft-switching schemes to control the hot atom damage and to improve the device lifetime dramatically. The damage mechanism should be generic in other Landau structures, such as microelectromechanical systems, nonvolatile memories, and analogous control strategies should improve the lifetime of all such bistable devices.