Exploring the Effects of Mo Doping on Oxygen Vacancy Formation and Uniformity in HfO₂- and ZrO₂-Based RRAMs

Abstract

Metal doping plays an important role in the resistance switching mechanism of the resistive random access memory (RRAM). The oxygen vacancy (V O ) formation energy under different oxygen partial pressures (P Od 2 ) and temperatures (T), the interaction of Mo dopant with V O , and the electronic structures of Mo-doped defect systems have been investigated by first-principles calculations. It is found that Mo doping significantly reduces the formation energy of neutral V O and decreases the stability of the +2 charged V O , especially in the Mo-doped HfO 2 system. Lower P Od 2 and higher T values are more energetically favorable to the formation of V O . The strong attraction between Mo and V O with charge states of 0 and +1q allows more oxygen vacancies to generate around the dopant, indicating that the Mo dopant can effectively modulate the distribution of V O , thus improving the uniformity of HfO 2 -and ZrO 2 -based RRAMs. The results of the electronic structures show that Mo doping can significantly enhance the conductivity of the devices; more electrons will be localized around the dopant, V O , and their surrounding atoms, thus promoting the formation of conductive filaments (CFs). It can be concluded that Mo doping can reduce the forming voltage and improve the resistance switching performance of HfO 2 -and ZrO 2 -based RRAMs, which provides theoretical guidance for the applications of metal-doped HfO 2 -and ZrO 2 -based RRAM devices.