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ZrN-Based Flexible Resistive Switching Memory
(2020-05-01)
Kumar, Dayanand
;
Chand, Umesh
;
Siang, Lew Wen
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
In this letter, ZrN-based resistive random access memory (RRAM) is investigated for flexible memory applications for the near future. Due to the room-temperature fabrication process, the device is suitable for low-temperature flexible monolithic technologies. The TiN/ZrN/TiN device exhibits excellent AC endurance cycling (10(7)), a rapid speed (45 ns) and stable retention (10(4) s) at 100 degrees C without any degradation. In addition, RRAM devices built with an additional HfN interface layer exhibit small operational voltage variations and stable switching characteristics. The flexibility of the device is excellent, and it maintains excellent electrical characteristics at a bending radius of up to 4 mm.
Improving linearity by introducing Al in HfO2 as a memristor synapse device
(2019-11-01)
Chandrasekaran, Sridhar
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Simanjuntak, Firman Mangasa
;
Saminathan, R.
;
Panda, Debashis
;
Tseng, Tseung-Yuen
Artificial synapse having good linearity is crucial to achieve an efficient learning process in neuromorphic computing. It is found that the synaptic linearity can be enhanced by engineering the doping region across the switching layer. The nonlinearity of potentiation and depression of the pure device is 36% and 91%, respectively; meanwhile, the nonlinearity after doping can be suppressed to be 22% (potentiation) and 60% (depression). Henceforth, the learning accuracy of the doped device is 91% with only 13 iterations; meanwhile, the pure device is 78%. A detailed conduction mechanism to understand this phenomenon is proposed.
One Bipolar Selector-One Resistor for Flexible Crossbar Memory Applications
(2019-03-01)
Kumar, Dayanand
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Aluguri, Rakesh
;
Chand, Umesh
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
A bipolar, highly nonlinear n-p-n selector is coupled in series with resistive switching memory device to suppress the sneak path current. The memory characteristics are measured for the crossbar array fabricated on a flexible polyethylene terephthalate substrate. Dominant conduction mechanism is the Zener tunneling to obtain the high nonlinearity in the selector device. This phenomenon validates the I-V characteristics which are temperature dependent, which leads to decrease in the turn-on voltage of the device as the temperature increases. The proposed one bipolar selector-one resistor device demonstrates better memory characteristics with the high nonlinearity (similar to 10(3)), observable memory window of about one order, excellent ac endurance (10(7)) cycles, fast switching speed (60 ns), and stable retention (10(4) s) at 100 degrees C. The results show the substantial potential of the proposedone selector-one-resistor structure in suppressing the leakage current, making it attractive for future high-density flexible crossbar memory array.
Low-Power and Highly Reliable Multilevel Operation in ZrO2 1T1R RRAM
(2011-08-01)
Wu, Ming-Chi
;
Lin, Yi-Wei
;
Jang, Wen-Yueh
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
The Ti/ZrO2/Pt resistive memory devices with one transistor and one resistor (1T1R) architecture are successfully fabricated in this letter. The tested devices show low operation current (20 mu A), low switching voltage (set/reset, 0.8/-1 V), and reliable data retention for low-resistance state (LRS) with a 20-mu A set current at 80 degrees C (over ten years) via an excellent current limiter, namely, a metal-oxide-semiconductor field-effect transistor (MOSFET). In addition, multilevel storage characteristics are also demonstrated by modulating the amplitude of the MOSFET gate voltage. The various LRS levels obtained are possibly attributed to the formation of different numbers and sizes of conducting filaments consisting of oxygen vacancies caused by an external electric field. Moreover, reproducible resistive switching characteristics up to 2000 switching cycles are achieved in the same device. Our 1T1R ZrO2-based resistive switching access memory with low-power and highly reliable multilevel operation has high potential for practical applications.
Peroxide induced volatile and non-volatile switching behavior in ZnO-based electrochemical metallization memory cell
(2017-09-20)
Simanjuntak, Firman Mangasa
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Chandrasekaran, Sridhar
;
Pattanayak, Bhaskar
;
Lin, Chun-Chieh
;
Tseng, Tseung-Yuen
We explore the use of cubic-zinc peroxide (ZnO2) as a switching material for electrochemical metallization memory (ECM) cell. The ZnO2 was synthesized with a simple peroxide surface treatment. Devices made without surface treatment exhibits a high leakage current due to the self-doped nature of the hexagonal-ZnO material. Thus, its switching behavior can only be observed when a very high current compliance is employed. The synthetic ZnO2 layer provides a sufficient resistivity to the Cu/ZnO2/ZnO/ITO devices. The high resistivity of ZnO2 encourages the formation of a conducting bridge to activate the switching behavior at a lower operation current. Volatile and non-volatile switching behaviors with sufficient endurance and an adequate memory window are observed in the surface-treated devices. The room temperature retention of more than 10(4) s confirms the non-volatility behavior of the devices. In addition, our proposed device structure is able to work at a lower operation current among other reported ZnO-based ECM cells.
Conductive bridge random access memory characteristics of SiCN based transparent device due to indium diffusion
(2018-03-23)
Kumar, Dayanand
;
Aluguri, Rakesh
;
Chand, Umesh
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
In this work, the transparent bipolar resistive switching characteristics of a SiCN-based ITO/ SiCN/AZO structure due to In diffusion from ITO is studied. The SiCN based device is found to be 80% transparent in the visible wavelength region. This device, with AZO as both top and bottom electrodes, does not show any RRAM property due to deposition of the high quality O-2-free SiCN film. Replacing the AZO top electrode with ITO in this device results in good resistive switching (RS) characteristics with a high on/off ratio and long retention. Replacing the SiCN film with ZrO2 also results in excellent RS characteristics due to the formation of an oxygen vacancies filament inside the ZrO2 film. A resistance ratio of on/off is found to be higher in the SiCN based device compared to that of the ZrO2 device. Diffusion of In from ITO into the SiCN film on application of high positive voltage during forming can be attributed to the occurrence of RS in the device, which is confirmed by the analyses of energy dispersive spectroscopy and secondary-ion mass spectrometry. This study shows a pathway for the fabrication of CBRAM based transparent devices for non-volatile memory application.
Role of nanorods insertion layer in ZnO-based electrochemical metallization memory cell
(2017-12-01)
Simanjuntak, Firman Mangasa
;
Singh, Pragya
;
Chandrasekaran, Sridhar
;
Lumbantoruan, Franky Juanda
;
Yang, Chih-Chieh
An engineering nanorod array in a ZnO-based electrochemical metallization device for nonvolatile memory applications was investigated. A hydrothermally synthesized nanorod layer was inserted into a Cu/ZnO/ITO device structure. Another device was fabricated without nanorods for comparison, and this device demonstrated a diode-like behavior with no switching behavior at a low current compliance (CC). The switching became clear only when the CC was increased to 75 mA. The insertion of a nanorods layer induced switching characteristics at a low operation current and improve the endurance and retention performances. The morphology of the nanorods may control the switching characteristics. A forming-free electrochemical metallization memory device having long switching cycles (> 10(4) cycles) with a sufficient memory window (10(3) times) for data storage application, good switching stability and sufficient retention was successfully fabricated by adjusting the morphology and defect concentration of the inserted nanorod layer. The nanorod layer not only contributed to inducing resistive switching characteristics but also acted as both a switching layer and a cation diffusion control layer.
Mechanism of Nonlinear Switching in HfO2-Based Crossbar RRAM With Inserting Large Bandgap Tunneling Barrier Layer
(2015-11-01)
Chand, Umesh
;
Huang, Kuan-Chang
;
Huang, Chun-Yang
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
In this paper, the nonlinear switching mechanism of the Ti/HfO2/Al2O3/TiN crossbar structure resistive random access memory device with good reliability is investigated. The nonlinearity of the device can be revealed by inserting a large bandgap of an Al2O3 thin layer between the TiN bottom electrode and the HfO2 switching film. The nonlinear switching mechanism caused by Flower-Nordheim tunneling involves the tunneling barrier of the Al2O3 layer. Besides, the nonlinear behavior is also sensitive to the thickness of the inserting Al2O3 layer. A high nonlinear factor of 37, large endurance more than 10(4), and good retention properties are achieved in the Ti/HfO2/Al2O3 (1-nm)/TiN structure.
Resistive switching mechanisms of V-doped SrZrO3 memory films
(2006-09-01)
Lin, Chun-Chieh
;
Tu, Bing-Chung
;
Lin, Chao-Cheng
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
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 H- to 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.
Effect of top electrode material on resistive switching properties of ZrO2 film memory devices
(2007-05-01)
Lin, Chih-Yang
;
Wu, Chen-Yu
;
Wu, Chung-Yi
;
Lee, Tzyh-Cheang
;
Yang, Fu-Liang
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.

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