Utilization of the t* Partial Switching Properties of Ferroelectrics in Memory Devices

Some ferroelectric materials exhibit a transition from stable to unstable partial switching at a critical pulsewidth t*. Schemes are proposed for utilizing this t* effect for coincident and successive addressing of a matrix memory, for a nondestructive readout from a matrix and for the simplification of a ferroelectric-electroluminescent display system. The practical limitations on these schemes are considered in terms of measurements made of t* in single crystal triglycine sulphate (TGS). Though the t* effect was observed to be a sharp rather than an absolute transition in the switching properties, the degree of sharpness was, however, sufficiently high to make t* devices feasible. For example, a coincidentally addressed t* TGS matrix can tolerate 105 disturb pulses. By comparison, a conventional matrix designed around the pseudocoercive field of TGS can only tolerate 10 disturbs. Even more impressive is that for the ``nondestructive'' type of readout operation 109 readouts can be made from a t* matrix before the stored information has to be rewritten.