Effects of top electrode material in hafnium-oxide-based memristive systems on highly-doped Si.

This work provides useful insights into the development of HfO-based memristive systems with a p-type silicon bottom electrode that are compatible with the complementary metal-oxide-semiconductor technology. The results obtained reveal the importance of the top electrode selection to achieve unique device characteristics. The Ag/HfO/Si devices have exhibited a larger memory window and self-compliance characteristics. On the other hand, the Au/HfO/Si devices have displayed substantial cycle-to-cycle variation in the ON-state conductance. These device characteristics can be used as an indicator for the design of resistive-switching devices in various scenes such as, memory, security, and sensing. The current-voltage (I-V) characteristics of Ag/HfO/Si and Au/HfO/Si devices under positive and negative bias conditions have provided valuable information on the ON and OFF states of the devices and the underlying resistive switching mechanisms. Repeatable, low-power, and forming-free bipolar resistive switching is obtained with both device structures, with the Au/HfO/Si devices displaying a poorer device-to-device reproducibility. Furthermore, the Au/HfO/Si devices have exhibited N-type negative differential resistance (NDR), suggesting Joule-heating activated migration of oxygen vacancies to be responsible for the SET process in the unstable unipolar mode.