Impact of Cu Electrode on Switching Behavior in a Cu/HfO₂/Pt Structure and Resultant Cu Ion Diffusion

Abstract

In a newly proposed switching device using polycrystalline HfO2 thin film with ion diffusion path, we have found that a Cu electrode could contribute to improved switching performance. Current–voltage measurements at room temperature revealed clear resistive switching, not accompanied by a forming process, in our Cu/HfO2/Pt structure. The current step difference from one state to the other one was in the order of 103–104, giving a sufficient on/off ratio. Voltage sweep polarity suggested that filamentary Cu paths were formed due to Cu ion diffusion and annihilated at the HfO2/Pt interface at reversed bias. This filament path formation and annihilation was the origin of the switching device performance.

Unipolar resistive switching with forming-free and self-rectifying effects in Cu/HfO2/n-Si devices

“…HfO 2 is selected due to its simple composition, and it can be prepared easily and HfO 2 -based RRAMs have been reported to show sub-ns operation speed and extremely outstanding endurance property, 1,26 thus exhibiting a very promising prospect for future application. With regard to top electrode, copper is chosen not only for its easy participation in the redox reaction to form Cu conductive filament (CF) in various kinds of storage media (e.g., oxides, 27 nitrides, 28 and organics 29 ) but also for its excellent compatibility with the conventional CMOS process. The experiment results show that forming-free unipolar Cu/HfO 2 /n-Si RRAMs own excellent self-rectifying effect with rectification ratio of ∼10 4 @ ±1 V and large OFF/ON ratio of ∼10 4 @ 1 V, accompanied with outstanding uniformity of cycles and devices.…”

Coexistence of bipolar and unipolar resistive switching in Al-doped ceria thin films for non-volatile memory applications

“…Hence, it would be advantageous to develop scalable material stacks exhibiting both the bipolar and unipolar resistive switching behaviors to expand the device application scope in nonvolatile memories. To improve the performance as well as to minimize dispersion in switching characteristics of ReRAM devices, a number of methods are being investigated such as interface control [6], metal doping [7], optimization process [8] and embedding nano-particles [9,10] are a few to mention. In this work, we have explored that the insertion of Al layer inside the two CeO 2 layers not only improves its resistive switching characteristics but also enables it to exhibit both bipolar and unipolar resistive switching behaviors.…”

Microstructural transitions in resistive random access memory composed of molybdenum oxide with copper during switching cycles

“…11,12 The SE material is usually sandwiched between an electrochemically active electrode (e.g., copper (Cu) or silver (Ag)) and an inactive electrode (e.g., platinum (Pt) or titanium nitride (TiN)). [18][19][20][21][22][23][24][25][26][27][28] The resistance switching is considered to occur because of the formation and rupture (or shrinkage) of CFs composed of Cu (or Ag), and this type of ReRAM is called the conductive bridge RAM (CBRAM). The molybdenum oxide (MoO x )-based device with the Cu electrode investigated in this report is a type of CBRAM, 29 while MoO x shows ReRAM switching behaviour even without the Cu electrode.…”