Resistive Switching Characteristics of HfOx/Al2O3 Nano-multilayers Structure Memristor Fabricated by Atomic Layer Deposition

We report a novel HfO
x
/Al
2
O
3
nano-multilayers (nano-MLs) structure memristor with ultrafast program/erase speed (50 ns), large memory window (~10
⁴
) and good pulse switching endurance (10
⁶
cycles) characteristics. Besides, 8 discrete resistance states can be successfully realized by controlling the Reset stop voltage (V
Reset-stop
). This indicates the potential capability to store 3 bits in each memristive cell. Through the analysis of the current-voltage (I-V) curves, a progressive decrease in conductance followed by a quantized conductance and finally a multilevel Reset phenomenon can be clearly observed in the Reset process. The Reset dynamics in our designed Ti/HfO
x
-Al
2
O
3
nano-MLs/Pt memristor can be interpreted as the evolution process of conductive filament as follows: gradually getting thinner followed by being atomic point contact, and eventually disconnecting layer by layer.