Influence of carrier concentration on the resistive switching characteristics of a ZnO-based memristor

Sandwich-style memristor devices were synthesized by electrochemical deposition with a ZnO film serving as the active layer between Al-doped ZnO (AZO) and Au electrodes. The carrier concentration of the ZnO films is controlled by adding HNO₃ during the growth process. A resulting increase in carrier concentration from 10¹⁷ to 10¹⁹ cm^–3 was observed, along with a corresponding drop in the on–off ratio from 6, 437% to 100%. The resistive switching characteristics completely disappeared when the carrier concentration was above 10¹⁹ cm^–3, making it unsuitable for a memory device. The decreasing switching ratio is attributed to a reduction in the driving force for oxygen vacancy drift. Systematic analysis of the migration of oxygen vacancies is presented, including the concentration gradient and electrical potential gradient. Such oxygen vacancy migration dynamics provide insight into the mechanisms of the oxygen vacancy drift and provide valuable information for industrial production of memristor devices.