High uniformity and forming-free ZnO-based transparent RRAM with HfO_x inserting layer

The impacts of HfOx inserting layer thickness on the electrical properties of the ZnO-based transparent resistance random access memory （TRRAM） device were investigated in this paper. The bipolar resistive switching behavior of a single ZnO film and bilayer HfOx/ZnO films as active layers for TRRAM devices was demonstrated. It was revealed that the bilayer TRRAM device with a 10-nm HfOx inserted layer had a more stable resistive switching behavior than other devices including the single layer device, as well as being forming free, and the transmittance was more than 80% in the visible region. For the HfOx/ZnO devices, the current conduction behavior was dominated by the space-charge-limited current mechanism in the low resistive state （LRS） and Schottky emission in the high resistive state （HRS）, while the mechanism for single layer devices was controlled by ohmic conduction in the LRS and Poole-Frenkel emission in the HRS.

Forming-free flexible memristor with multilevel storage for neuromorphic computing by full PVD technique

Flexible resistive random access memory(RRAM) has shown great potential in wearable electronics.With tunable multilevel resistance states,flexible memristors could be used to mimic the bio-synapses for constructing high-efficient wearable neuromorphic computing system.However,the flexible substrate has intrinsic disadvantages including low-tempe rature tolerance and poor complementary metal-oxidesemiconductor(CMOS) compatibility,which limit the development of flexible electronics.The physical vapor deposition(PVD) fabrication process could prepare RRAM without requirement of further treatment,which greatly simplified preparation steps and reduced the production costs.On the other hand,forming process,as a common pre-programing operation in RRAM,increases the energy consumption and limits the application scenarios of RRAM.Here,a NiO-based forming-free RRAM with low set voltage was fabricated via full PVD technique.The flexible device exhibited reliable re sistive switching characteristics under flat state even compre s sive and tensile states(R=10 mm).The tunable multilevel resistance states(5 levels) could be obtained by controlling the compliance current.Besides,synaptic plasticities also were verified in this device.The flexible NiO-based RRAM shows great potential in wearable forming-free multibit memo ry and neuromorphic computing electronics.