Optimal migration route of Cu in HfO2

The movement of Cu in a HfO 2 -based resistive random access memory (RRAM) device is investigated in depth by first-principle calculations. Thermodynamics analysis shows that the dominant motion of Cu tends to be along the [001] orientation with a faster speed. The migration barriers along different routes are compared and reveal that the [001] orientation is the optimal migration route of Cu in HfO 2 , which is more favorable for Cu transportation. Furthermore, the preferable HfO 2 growth orientation along [100], corresponding to Cu migration along [001], is also observed. Therefore, it is proposed that the HfO 2 material should grow along [100] and the operating voltage should be applied along [001], which will contribute to the improvement of the response speed and the reduction of power consumption of RRAM.