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This study determines the relationship between retention and endurance reliability for a HfOx-based resistive random access memory (ReRAM). A TiN (15 nm) / HfOx (6 nm) / Ti (10 nm) / TiN (40 nm) stacked structure is fabricated and tested to verify its basic characteristics and reliability. The high resistance states (HRS) retention behavior is characterized and is found to degrade over 100x on the endured bits because there is a sequential high temperature procedure. The degradation is reduced slightly to a ~30x drop for the endured devices with one single refresh cycle. During the endurance and retention test procedures, the HRS resistance decreases because neutral oxygen vacancy filaments grow and this cannot be reversed. The I-V characteristics for endured devices are also determined. The results show that isothermal treatment causes a gradual SET and RESET process with multiple feasible states. The thermally induced filament degradation model (isolated filament vs. continuous filament) is verified by the relationship between retention and endurance reliability. Design guidance is recommended for an improvement in ReRAM reliability.

A SET-state conductance change in a hafnium-oxide resistive switching memory cell due to repeated read events is investigated. We characterize a read-induced conductance change at different read voltages and SET-state conductance levels. Our result shows that the read-induced conductance degradation exhibits a two-stage evolution with the read pulse number. A SET-state conductance decreases slightly in the first stage and then follows inverse power-law dependence on the read number in the second stage. The power factor is an exponential function of a read voltage without regard to the SET-state conductance level, and the read pulse number at the transition of the two stages is related to a read voltage and conductance level. An analytical model to describe the two-stage conductance evolution is proposed. The parameters in the model are extracted from measurement data. Our model is verified by good agreement between the modeled and measured results in a wide range of read pulse number, read voltage, and SET-state conductance level.

In this study, ZrO2 formed by the nitric acid oxidation method is proposed to be the tunneling oxide for nonvolatile memory device applications. The sputtered Zr thin film was oxidized by immersing in the nitric acid solution (HNO3:H2O = 1:10) for 60 s at room temperature. The quality of the formed ZrO2 was also extracted by the capacitance-voltage and current density-voltage measurements. Then, X-ray photoelectron spectroscopy has been used to confirm that the deposited Zr can be oxidized completely after the oxidation process. Moreover, a CoSi2 thin film was deposited on the nitric acid oxidized ZrO2 as the self-assembled layer of the memory device. After the device fabrication, the electrical and material characteristics of the CoSi2 nanocrystal memory devices have also been demonstrated and discussed.

High magnetization (Mr) and enhanced coercivity magneto-optical (MO) recording media TbFeCo (TFC) were investigated for hybrid magnetic flux reading/optical recording due to their large magnetic flux. To increase the stability of high Mr TFC media, dual-layer disks composed of TM-rich readout layer with saturation magnetization (MS)=370 emu/cm/sup 3/ and RE-rich memory layer were fabricated. Coercivity and interface energy between double layers as a function of active layer thickness were examined. By simulating thermo-magnetic writing, the dual-layer media were shown to be applicable for optical writing/magnetic flux reading recording.

The resistive switching behaviors of sputtered V-doped SrZrO3 (V:SZO) memory films were investigated in this letter. The current states of the memory films were switched between high current state (H-state) and low current state (L-state). The resistance ratio of the two current states was over 1000 at a read voltage. The switching mechanism from L- to H-state corresponds to the formation of current paths. However, this mechanism from Hto L-state is thought to be due to the fact that the defects present in the V:SZO film randomly trap electrons, and hence, the current paths are ruptured. The conduction mechanism of the H-state is dominated by ohmic conduction, whereas the L-state conduction is dominated by Frenkel-Poole emission. The polarity direction of the resistive switching is an intrinsic property of the SrZrO3 oxides. The V:SZO films with high uniformity and good stability are expected to be used in nonvolatile memory

The microwave sintering (ms) process is observed to be superior to conventional sintering (cs) in the densification of Y/sub 3/Fe/sub 5/O/sub 12/ materials. A density of 97.3% theoretical density (T.D.) with pure garnet phase and small grain size (5/spl sim/7 /spl mu/m) was obtained for materials microwave sintered at 1300/spl deg/C for 20 minutes. By contrast, only 94.3% of T.D. can be reached for materials sintered by conventional processing at 1425/spl deg/C for 8 h and the grains are large (/spl sim/25 /spl mu/m). A higher densification rate in the microwave sintering process, as compared with that in conventional sintering processing, is ascribed to the lower activation energy of densification (i.e., (E/sub a/)/sub ms/=83.3 kcal/mol and (E/sub a/)/sub cs/=163.2 kcal/mol). On the other hand, small grain size in microwave sintered samples is attributed to the fact that the (E/sub a/)/sub ms/-value is smaller than the activation energy of grain boundary migration (E/sub g/=94.8 kcal/mol).