switching memory devices using a low-cost process. Considering the CsPbX3 perovskites are usually prepared by solution method, point defects such as vacancies, interstitials, and antisites are possible in the crystals. These defects are essential for the defect drift-dominated resistive switching memory. Thus, these CsPbX3 perovskites have great potential for application in memory devices. Given the fact that resistance switching in halide perovskite-based RRAM is caused by migrations of halide atoms through vacancies, the migration characteristics of a vacancy within the RRAM are one of the most important material properties of the RRAM determining the key features of it. However, despite its importance, the activation energy of halide vacancy in RRAMs has been no serious study topic at all. Obviously, a small activation barrier of halide vacancy expected in halide perovskite-based RRAMs plays a central role in allowing this RRAM to operate at low voltages and thus at low power consumption mode. Demonstrations Papers at the IEDM Conference in 2007 suggested for the first time that ReRAM exhibits lower programming currents than PRAM or MRAM without sacrificing programming performance, retention or endurance. Some commonly cited ReRAM systems are described further below. HfO2-based ReRAM At IEDM 2008, the highest-performance ReRAM technology to date was demonstrated by ITRI using HfO2 with a Ti buffer layer, showing switching times less than 10 ns and currents less than 30μA. At IEDM 2010, ITRI again broke the speed record, showing <0.3 ns switching time, while also showing process and operation improvements to allow yield up to 100% and endurance up to 10 billion cycles. IMEC presented updates of their ReRAM program at the 2012 Symposia on VLSI Technology and Circuits, including a solution with a 500 nA operating current. ITRI had focused on the Ti/HfO2 system since its first publication in 2008. ITRI's patent 8362454 has since been sold to TSMC; the number of prior licensees is unknown. On the other hand, IMEC focused mainly on Hf/HfO2. Winbond had done more recent work toward advancing and commercializing the HfO2-based ReRAM. Panasonic Panasonic revealed its TaOx-based ReRAM at IEDM 2008. A key requirement was the need for a high work function metal such as Pt or Ir to interface with the TaOx layer. The change of O content results in resistance change as well as Schottky barrier change. More recently, a Ta2O5/TaOx layer was implemented, which still requires the high work function metal to interface with Ta2O5.