Browsing by Author "Lin, Chun-An"

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Effect of barrier layer on switching polarity of ZrO2-based conducting-bridge random access memory
(2017-09-11)
Chandrasekaran, Sridhar
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Simanjuntak, Firman Mangasa
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Tsai, Tsung-Ling
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Lin, Chun-An
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Tseng, Tseung-Yuen
In this study, metal diffusion barrier-dependent switching polarity in ZrO2-based conducting-bridge random access memory was investigated. The device without the barrier layer (BL) exhibited nonpolar switching characteristics. However, inserting TiW BL resulted in positive reset failure. This phenomenon depends on the size and shape of the conducting bridge and also on the defects that contribute to the formation and rupture of the bridge. Consequently, the properties of the conducting bridge govern the device switching performance. Cu- and oxygen vacancy-based conducting bridge during N-Set for a device with and without the BL was proposed. The effect of the insertion of BL on the switching performance was also discussed. The absence of BL resulted in switching instability and poor nonvolatility. By contrast, a device with BL exhibited enhanced uniformity and nonvolatility, and the retention was more than 10(5) s at 200 degrees C. Published by AIP Publishing.
Enhanced switching uniformity in AZO/ZnO1-x/ITO transparent resistive memory devices by bipolar double forming
(2015-07-20)
Simanjuntak, Firman Mangasa
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Panda, Debashis
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Tsai, Tsung-Ling
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Lin, Chun-An
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Wei, Kung-Hwa
The influence of single and double forming on the switching stability of AZO/ZnO1-x/ITO transparent resistive memory devices was investigated. Devices that underwent single forming exhibited severe switching instability, where as those that underwent double forming exhibited excellent switching uniformity. The quantity of conducting filaments can be limited by applying the two-step forming process. Consequently, the set/reset process can be controlled, enhancing switching stability. Satisfactory endurance with an acceptable ON/OFF ratio of 10(2) and satisfactory retention behavior of 10(4)s at room temperature confirmed the reliability of optimized devices. Furthermore, highly transparent devices (transparency of approximately 85% in visible range) have been fabricated. (C) 2015 AIP Publishing LLC.
Enhancing the memory window of AZO/ZnO/ITO transparent resistive switching devices by modulating the oxygen vacancy concentration of the top electrode
(2015-11-01)
Simanjuntak, Firman Mangasa
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Panda, Debashis
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Tsai, Tsung-Ling
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Lin, Chun-An
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Wei, Kung-Hwa
The effect of a defect concentration-modified top electrode on the bipolar resistance switching of transparent Al-doped ZnO/ZnO/ITO [AZO(TE)/ZnO/ITO(BE)] devices was investigated. Different oxygen vacancy concentrations in the top electrode, Al-doped ZnO, can be simply controlled by modulating the sputtering working pressure condition from 1.2 to 12 mTorr. The oxygen vacancy concentration between AZO and ZnO may trigger oxygen diffusion at the interface and affect the switching characteristic. High oxygen release from a ZnO resistive layer caused by excessive oxygen vacancy concentration at the top electrode is responsible for reducing the memory window as a result of reduced oxygen available to rupture the filament. Top electrode based on lower oxygen vacancy concentration has a higher memory window and an asymmetric resistive switching characteristic. However, all set of devices have excellent endurance of more than 10(4) cycles. This study showed that an Al-doped ZnO top electrode helps not only to achieve a transparent device but also to enhance memory properties by providing a suitable oxygen vacancy concentration.
Forming-free bipolar resistive switching in nonstoichiometric ceria films
(2014-01-27)
Ismail, Muhammad
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Huang, Chun-Yang
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Panda, Debashis
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Hung, Chung-Jung
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Tsai, Tsung-Ling
The mechanism of forming-free bipolar resistive switching in a Zr/CeO (x) /Pt device was investigated. High-resolution transmission electron microscopy and energy-dispersive spectroscopy analysis indicated the formation of a ZrO (y) layer at the Zr/CeO (x) interface. X-ray diffraction studies of CeO (x) films revealed that they consist of nano-polycrystals embedded in a disordered lattice. The observed resistive switching was suggested to be linked with the formation and rupture of conductive filaments constituted by oxygen vacancies in the CeO (x) film and in the nonstoichiometric ZrO (y) interfacial layer. X-ray photoelectron spectroscopy study confirmed the presence of oxygen vacancies in both of the said regions. In the low-resistance ON state, the electrical conduction was found to be of ohmic nature, while the high-resistance OFF state was governed by trap-controlled space charge-limited mechanism. The stable resistive switching behavior and long retention times with an acceptable resistance ratio enable the device for its application in future nonvolatile resistive random access memory (RRAM).
Impact of barrier layer on HfO2-based conductive bridge random access memory
(2019-03-04)
Lin, Chun-An
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Huang, Chu-Jie
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this letter, we report the impact of the barrier layer on the performance of HfO2-based conductive bridge RAM (CBRAM) devices with TeTiW as the source layer. The considerable improvement of retention in the CBRAM device using TiW as the barrier layer is attributed to the lower amount of oxygen vacancies in the switching layer, which is justified from the O1s core level in X-ray photoelectron spectroscopy analyses. Therefore, the diffusion of Te in the resistive layer of the device with the TiW barrier layer is limited even at high temperature. The TeTiW/TiW/HfO2/TiN CBRAM device provides an excellent endurance of more than 10(4) cycles, with an on/off ratio of 200. Such a device also features long retention for up to 10(4) s at 200 degrees C.
Impacts of Co doping on ZnO transparent switching memory device characteristics
(2016-05-02)
Simanjuntak, Firman Mangasa
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Prasad, Om Kumar
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Panda, Debashis
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Lin, Chun-An
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Tsai, Tsung-Ling
The resistive switching characteristics of indium tin oxide (ITO)/Zn1-xCoxO/ITO transparent resistive memory devices were investigated. An appropriate amount of cobalt dopant in ZnO resistive layer demonstrated sufficient memory window and switching stability. In contrast, pure ZnO devices demonstrated a poor memory window, and using an excessive dopant concentration led to switching instability. To achieve suitable memory performance, relying only on controlling defect concentrations is insufficient; the grain growth orientation of the resistive layer must also be considered. Stable endurance with an ON/OFF ratio of more than one order of magnitude during 5000 cycles confirmed that the Co-doped ZnO device is a suitable candidate for resistive random access memory application. Additionally, fully transparent devices with a high transmittance of up to 90% at wavelength of 550 nm have been fabricated. Published by AIP Publishing.
IMPROVEMENT OF RESISTIVE SWITCHING PROPERTIES OF Ti/ZrO2/Pt WITH EMBEDDED GERMANIUM
(2014-01-01)
Lin, Chun-An
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Panda, Debashis
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this study, we construct the Ti/ZrO2/Ge(5nm)/ZrO2/Pt structures with various positions of embedded Ge in ZrO2 films. After depositing a Ge layer, a 600 degrees C rapid thermal annealing is carried out. Compared to other Ge positions, the lowest forming voltage and the most stable resistive behavior are observed in the cell with a Ge layer near the top electrode. The curve fitting of high resistance state and low resistance state shows that Schottky emission in reset process and the ionic conduction during set process. The improved switching properties could be related to the formation of Gerrnanium oxide and the defect concentration reduction after annealing process.
Resistive Switching Characteristics and Reliability of SiNx-Based Conductive Bridge Random Access Memory
(2018-09-01)
Lin, Chun-An
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Dai, Guang-Jyun
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The switching properties of Te and TeTiW top electrodes (TEs) on TiW/SitsifTiN resistive switching memory devices are explored in this paper. The TeTiW TE device exhibits more favorable bipolar resistive switching behavior because of the decrease in binding energy after its use. This finding is confirmed through X-ray photoelectron spectroscopy analyses. The filament of the TeTiW TE device is metal like after forming, and the reset process corresponds with the thermal-dissolution mechanism. A physical model based on a Te filament is constructed to explain such phenomena. The TeTiW TE device provides the excellent endurance of more than 10(4) cycles, with an ON/OFF ratio of 500. The improvement can be attributed to the filament's robustness during the forming and set processes, which prevent its diffusion even at high temperature. The device also features long retention for up to 10(4) sat 225 degrees C without stress, and 10(4) s at 85 degrees C with stress of -0.3 V. Therefore, it has high potential for high-density nonvolatile memory applications.
Resistive switching characteristics of Pt/CeOx/TiN memory device
(2014-06-01)
Ismail, Muhammad
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Talib, Ijaz
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Huang, Chun-Yang
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Hung, Chung-Jung
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Tsai, Tsung-Ling
The resistive switching characteristics of Pt/CeOx/TiN memory devices are investigated for potential applications in nonvolatile resistive random access memory (RRAM). The X-ray diffraction characteristics of the sputtered CeOx layer indicate the formation of nanocrystalline single-phase CeO2 with a cubic fluorite structure. The existence of oxygen vacancies in the Pt/CeOx/TiN memory device was determined by X-ray photoelectron spectroscopic studies, while the presence of an interfacial layer between CeOx and the TiN bottom electrode was investigated by Xray diffraction and high resolution transmission electron microscopy. The TiON layer formed at the TiN/CeOx interface seems to play a key role in the resistive switching mechanism of the device. The present CeOx-based device shows excellent bipolar resistive switching characteristics, including a low operation current (100 mu A), high ON/OFF resistance ratio (similar to 10(5)), and good retention/stress characteristics at both room temperature and 85 degrees C. (C) 2014 The Japan Society of Applied Physics
Switching mechanism of double forming process phenomenon in ZrOx/HfOy bilayer resistive switching memory structure with large endurance
(2014-02-10)
Huang, Chun-Yang
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Huang, Chung-Yu
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Tsai, Tsung-Ling
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Lin, Chun-An
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Tseng, Tseung-Yuen
In this Letter, the mechanism of double forming process phenomenon revealing in ZrO2/HfO2 bilayer resistive random access memory structure is investigated. This phenomenon caused by the formation of TiON interfacial layer can be well explained by using the energy band diagram. The TiON interfacial layer will be a tunneling barrier during the first forming process when a negative voltage applied on the device, while it will breakdown when applying a positive voltage. Besides, due to the double forming process, an asymmetric conductive filament with narrower size at ZrO2/HfO2 interface is formed in the device. The point for formation and rupture of the conductive filament can be confined at the ZrO2/HfO2 interface, and it will suppress the consumption of oxygen ions during endurance test. Therefore, high speed (40 ns) and large endurance (10(7) cycles) characteristics are achieved in this device structure. (C) 2014 AIP Publishing LLC.