Chih-Yang Lin

Effect of Top Electrode Material on Resistive Switching Properties of

The influence of top electrode material on the resistive switching properties of ZrO2-based memory film using Pt as a bottom electrode was investigated in this letter. In comparison with Pt/ZrO2/Pt and Al/ZrO2/Pt devices, the Ti/ZrO2/Pt device exhibits different resistive switching current-voltage (I- V) curve, which can be traced and reproduced by a dc voltage more than 1000 times only showing a little decrease of resistance ratio between high and low resistance states. Furthermore, the broad dispersions of resistive switching characteristics in the Pt/ZrO2/Pt and Al/ZrO2/Pt devices are generally observed during successive resistive switching, but those dispersions are suppressed by the device using Ti as a top electrode. The reliability results, such as cycling endurance and continuous readout test, are also presented. The write-read-erase-read operations can be over 104 cycles without degradation. No data loss is found upon successive readout after performing various endurance cycles

\hbox{ZrO}_{2}

In this study, we investigate the resistive switching behavior of radio frequency (rf)-sputtered Al 2 O 3 thin films. It is observed that both high-conducting state (ON state) and low-conducting state (OFF state) are stable and reproducible during successive resistive switchings by dc voltage sweeping. The ratio of resistance of the ON and OFF state is over 10 3 . Such a reproducible resistive switching can be performed at 150°C, and the resistance of the ON state can be altered by various current compliances. The conduction mechanisms of the ON and OFF states are demonstrated as ohmic conduction and Frenkel-Poole emission, respectively. Both states, performed by dc voltage sweeping and applying short pulse, are stable over 10 4 s at a read voltage of 0.3 V and the electrical-pulse-induced resistance change (EPIR) phenomenon is demonstrated, which are all important properties for further resistive random access memory application.

Film Memory Devices

The influence of Ti top electrode material on the resistive switching properties of ZrO2-based memory film using Pt as bottom electrode was investigated in the present study. When Ti is used as top electrode, the resistive switching behavior becomes dependent on bias polarity and no current compliance is needed during switching into high conducting state. This phenomenon is attributed to the fact that a series resistance between Ti and ZrO2 film, composed of a TiOx layer, a ZrOy layer, and even the contact resistance, imposed a current compliance on the memory device. Besides, our experimental results imply that switching the device into high conducting state is a field driven process while switching back into low conducting state is a current driven process.

Bistable Resistive Switching in Al2O3 Memory Thin Films

In this study, we propose a simple method to produce the various interface thicknesses within Ti/ZrO2 by changing the thickness of the Ti top electrode. As the Ti thickness increases, the induced interface thickness also increases to degrade the dielectric strength of the ZrO2, further lowering the forming voltage. However, when the interface layer is thick enough, it will trap sufficient charges to build up an opposite electric field to increase the forming voltage. The induced interface thickness is found to obviously affect the bias polarity of the resistive switching behavior and the device reliability. A fluctuant ON process is also demonstrated to be attributed to the competition between the formation and rupture of the conducting filaments.

Modified resistive switching behavior of ZrO2 memory films based on the interface layer formed by using Ti top electrode

In this paper, nonpolar resistive switching behavior is reported for the first time in a SZO-based memory device. The electrode materials used which have different conductivities affect the resistive switching properties of the device. The Al/V:SZO-LNO/Pt device shows nonpolar switching behavior, whereas the Al/V:SZO/LNO device has bipolar switching property. The resistance ratios of these two devices are quite distinct owing to the difference between the resistance of low resistance states. The Al/V:SZO-LNO/Pt device with lower resistive switching voltages (mnplus7 V turn on and mnplus2 V turn off) and higher resistance ratio is more suitable for practical applications compared to the Al/V:SZO/LNO device. The switching speed of the Al/V:SZO-LNO/Pt device is 10 ns, which is the fastest speed that has ever been reported. The conduction mechanisms, nondestructive readout property, retention time, and endurance of this device are also reported in this paper.

Effects of Ti top electrode thickness on the resistive switching behaviors of rf-sputtered ZrO2 memory films

The resistive switching mechanisms of ZrO 2 memory films are proposed to explain why resistive switching characteristics of Ti/ZrO 2 /Pt device are more stable than those of Pt/ZrO 2 /Pt and Al/ZrO 2 /Pt devices in this study. Different from the Pt/ZrO 2 /Pt and the Al/ZrO 2 /Pt devices, the carrier conduction mechanisms in the Ti/ZrO 2 /Pt device obey space charge limited current theory, which may be caused by the formation of the interface layer between Ti and ZrO 2 . Moreover, the resistive switching mechanisms are proposed to be related to the filament formation/rupture theory and oxygen ion migration. The location where filament formation/rupture takes place should be confined near the interface between Ti and ZrO 2 , leading to the stable resistive switching characteristics and a better endurance performance. During successive resistive cycles at room temperature and 150°C, the fatigue behaviors are observed due to the degradation of both two memory states, which might be related to the transformation of the interface layers between Ti and ZrO 2 and the coalescence of ZrO x clusters.

Voltage-Polarity-Independent and High-Speed Resistive Switching Properties of V-Doped

The stabilization of the resistive switching properties is necessary to realize the memory application of the SrZrO3(SZO)-based resistive switching devices. During continuous resistive switching cycle, broad variations of the resistive switching parameters of the SZO-based memory devices can be improved by a thin embedded Cr layer. The Cr metal layer is proposed to diffuse into and dope the SZO thin film to produce the space charge region, further reducing the effective resistive switching region. Hence, the good stabilization of the resistive switching properties can be obtained in the SZO films with embedded Cr layer.