Flat-band voltage hysteresis of MNOS structures

A shift of the flat-band voltage of metal–nitride–oxide–silicon (MNOS) elements connected with a hysteresis effect, is observed when voltage pulses exceeding a certain threshold amplitude are applied. The hysteresis behaviour is orientated in such a sense that the flat-band shifts to positive flat-band voltages with positive voltages applied, and to the reverse direction with negative voltages applied. The flat-band voltage shift is stable for voltages below the threshold voltage. Therefore, the flat-band state can be investigated without altering it. The shortest pulse times producing an effect are in the order of 1 μs. Elements with aluminium as a metal contact show a secondary effect, i.e. the flat-band voltage was changed to positive values with negative pulses. No considerable change in the course of the hysteresis effect was found at lower temperatures.