Ferroelectric behavior and reproducible Bi-stable resistance switching property in K-doped ZnO thin films as candidate for application in non-volatile memories

• Semiconducting ferroelectric properties in potassium-doped ZnO thin films are reported.
• Wave forms showing the applied input Vi and output Vo obtained for Al/ZnO:K/ITO structures evidencing real time hysteresis loop.
• Polarization versus voltage curve recorded for ZnO:K thin films.
• The reproducible bi-stable resistance switching phenomenon was observed for several cycles.
• No saturation is easily observed for ferroelectric loop as it is common in ferroelectric semiconductor.

Potassium-doped ZnO thin films electrodeposited on indium tin oxide (ITO) coated glass substrates exhibited ferroelectric behavior with a remnant polarization of 0.2 µC/cm2. Especially, wave forms showing the applied input voltage Vi and output voltage Vo were obtained for Al/ZnO:K/ITO structure. It exhibits a superposition of Vi (input) and Vo (output) signal from Al/ZnO:K/ITO structure with a clear phase shift between the two wave forms which again confirms that the observed ferroelectric hysteresis curve is not related to leaky dielectric materials. The current–voltage characteristics of Al/ZnO:K/ITO structures measured for several cycles revealed bi-stable switching characteristics. The reproducible bi-stable switching characteristics for the mentioned structures had good retention in one particular resistance state. Around one order of switching was realized between low and high resistance states. The switching property thought to be polarization induced originating out from the ferroelectric properties of the potassium doped ZnO thin film. The switching between ZnO:K/ITO interface is assumed to be critical for stability in switching for several cycles. Possible application of this structure in non-volatile memories is explored.