TaO x -based resistive switching memories: prospective and challenges
© Prakash et al.; licensee Springer. 2013
Received: 9 August 2013
Accepted: 1 September 2013
Published: 9 October 2013
Resistive switching memories (RRAMs) are attractive for replacement of conventional flash in the future. Although different switching materials have been reported; however, low-current operated devices (<100 μA) are necessary for productive RRAM applications. Therefore, TaO x is one of the prospective switching materials because of two stable phases of TaO2 and Ta2O5, which can also control the stable low- and high-resistance states. Long program/erase endurance and data retention at high temperature under low-current operation are also reported in published literature. So far, bilayered TaO x with inert electrodes (Pt and/or Ir) or single layer TaO x with semi-reactive electrodes (W and Ti/W or Ta/Pt) is proposed for real RRAM applications. It is found that the memory characteristics at current compliance (CC) of 80 μA is acceptable for real application; however, data are becoming worst at CC of 10 μA. Therefore, it is very challenging to reduce the operation current (few microampere) of the RRAM devices. This study investigates the switching mode, mechanism, and performance of low-current operated TaO x -based devices as compared to other RRAM devices. This topical review will not only help for application of TaO x -based nanoscale RRAM devices but also encourage researcher to overcome the challenges in the future production.
KeywordsResistive switching Memory TaO x RRAM
This topical review investigates the switching mode, mechanism, and performances of the TaO x -based devices as compared to other RRAMs in literature. Long program/erase endurance and data retention of >85°C with high yield have a greater prospective of TaO x -based nanoscale RRAM devices; however, lower current (few microampere) operation is very challenging for practical application, which is reviewed in detail here.
Resistive RAM overview
Switching modes: unipolar/bipolar
Resistive switching mechanism
Further, depending on the switching material and electrodes, the resistive switching memory can be divided into two types: cation-based switching called electrochemical metallization (ECM) memory and anion-based switching called valance change memory (VCM) . In cation-based memory, a solid-electrolyte was used as a switching material and an electrochemically active metal such as copper (Cu), silver (Ag), and Nickel (Ni) as TE and an inert metal as BE . Generally, the ions of Cu and Ag were known as mobile ions. When positive voltage was applied on the Cu TE, for example, metallic Cu was reduced electrochemically to give Cu+ ions generated from metallic Cu due to anodic dissolution. These ions then diffused through the solid electrolyte due to electric field and reached to the BE where these ions reduced to become metallic Cu and electro-crystallize on the BE. As a result, a conducting filament grew preferentially from the BE and finally bridge the BE and TE. Consequently, the device switched to the LRS. That is the reason that ECM devices were also called conducting bridge RAM. When negative voltage was applied on the TE electrode, the Cu filament broken due to electrochemical dissolution reaction initiated by an electronic current through the metallic bridge, and, in parallel, an electrochemical current and the device came into HRS. In recent years, many solid electrolyte materials such as GeSe x [11, 59, 60], GeS [61, 62], Cu2S , Ag2S , Ta2O5[65, 66], SiO2, TiO2, ZrO2, HfO2, GeO x , MoO x /GdO x , TiO x /TaSiO y , GeSe x /TaO x , CuTe/Al2O3, and Ti/TaO x  were reported. The VCM devices consist of a sub-stoichiometric switching material and an inert electrode such as Pt, Ir, Au, etc., or reactive electrode such as W, Al, Ti, Ni, etc. In VCM devices, switching occurs due to the redox reaction induced by anion (O2-) migration to form conducting filament, as shown in Figure 4a. These devices usually need a forming step in order to switch between LRS and HRS reversibly [17, 21]. During electroforming process, the generation of oxygen O2- ions occurs in the switching material due to chemical bond breaking. The generated O2- ions migrate toward the TE under the external bias, and oxygen gas evolution at the anode due to anodic reaction are also reported in literature. To maintain the charge neutrality, the valance state of the cations changes. Therefore, it is called VCM memory. Due to O2- ion generation and anodic reaction, oxygen vacancy conducting path generates in the switching material between TE and BE, and device switches to LRS. The electroforming conditions strongly depend on the dimension of the sample, in particular, the switching material thickness. In addition, thermal effects play an essential role in the electroforming, and it sometimes damage the devices by introducing morphological changes [17, 21]. Partially blown electrodes during forming have been observed . Thus, the high-voltage forming step needs to be eliminated in order to product the RRAM devices in future. However, anion-based switching material with combination of different electrode materials and interface engineering will have good flexibility to obtain proper RRAM device.
Switching materials and SET/RESET current in published literature
RRAM materials with structure
Kim et al. 
Ielmini et al. 
Jousseaume et al. 
Yang et al. 
Pt/Ti/TiO2/W and Pt/W/TiO2/W
0.5 and 3 mA
Harmes et al. 
Ir/TiO x /TiN
Park et al. 
TiN/TiO x /HfO x /TiN
Pt/ZrO x /HfO x /TiN
Lee et al. 
Walczyk et al. 
Chen et al. 
TiN/TiON/HfO x /Pt
Yu et al. 
Ni or Co/Cu2O/Cu
Chen et al. 
Au or Pt/SrTiO3/Au or Pt
2.8 ± 0.8 mA
2.5 ± 0.5 mA
Szot et al. 
Sun et al. 
30 mA (self)
Lin et al. 
Liu et al. 
Wang et al. 
Wang et al. 
TiON/WO x /W/TiN
Ho et al. 
TiN/WO x /W
Chien et al. 
Pt/WO x /W
Kim et al. 
Lin et al. 
Wu et al. 
IrO x /Al2O3/IrO x ND/Al2O3/IrO x
Banerjee et al. 
Qinan et al. 
Peng et al. 
Andy et al. 
Chiu et al. 
Peng et al. 
TiW/SiO x /TiW
Yao et al. 
n-Si/SiO x /p-Si
Mehonic et al. 
Cao et al. 
IrO x /GdO x /WO x /W
Jana et al. 
Seong et al. 
Ni/GeO x /HfON/TaN
0.1 μA (self)
Cheng et al. 
IrO x /Al2O3/GeNWs/SiO2/p-Si
Prakash et al. 
Pt/TaO x /Pt
Wei et al. 
IrO x /TaO x /WO x /W
Prakash et al. 
Ta/TaO x /Pt
Yang et al. 
Lee et al. 
A schematic potential energy curve for TaO x is reported by Wei et al. . This implies that both the HRS and the LRS of TaO x are stable owing to small difference of Gibbs free energy in between LRS and HRS, and the barrier height between these states is quite high. Due to these benefits of TaO x switching material, it is important to design RRAM for real application. That is why this material has been studied in this review below.
Resistive RAM using TaO x material
Data comparison in published literature
Device size (μm2)
Set/reset voltage (V)
Current compliance (μA)
W/TiO x /TaO x /TiN 
0.15 × 0.15
>3 h, 85°C
0.5 × 0.5
50 × 50-0.03 × 0.03
10 years, 85°C
4 × 4
~0.4 × 0.4-0.03 × 0.03
Hf, Ti, Ta/HfO2/TiN 
0.04 × 0.04
0.01 × 0.01
5 × 107
Pt/ZrO x /HfO x /TiN 
0.05 × 0.05
TiN/WO x /TiN 
0.06 × 0.06
2 × 103 h, 150°C
It is reviewed that TaO x -based bipolar resistive switching memory could be operated at a low current of 80 μA [41, 109], which has prospective of RRAM applications in the future. Further, TaO x is a simple and useful material because of two stable phases of TaO2 and Ta2O5, as compared to other reported materials. Long program/erase endurance of >1010 and 10 years data retention are also reported in published literature [31, 110]. So far, bilayered TaO x with inert electrodes (Pt and/or Ir) or single-layer TaO x with semi-reactive electrodes (W and Ti/W or Ta/Pt) are reported; however, conducting nano-filament formation/rupture is controlled by oxygen ion migration through bilayered or interfacial layer design under external bias. Further, high-density memory with a small size of 30 × 30 nm2 could be designed using crossbar architecture . It is found that the memory performance is becoming worst at operation current of 10 μA. Therefore, it is very challenging to reduce the operation current (few microampere) of the RRAM devices. So far, good performance of TaO x -based resistive switching memory devices is investigated, as compared to other switching materials in different RRAMs. This topical review shows good prospective; however, it needs to overcome the challenges for future production of the TaO x -based nanoscale RRAM application.
This work was supported by the National Science Council (NSC), Taiwan, under contract numbers: NSC-101-2221-E-182-061 and NSC-102-2221-E-182-057-MY2. The authors thank Electronic and Optoelectronic Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan, for their experimental support.
- Hutchby J, Garner M: Assessment of the potential & maturity of selected emerging research memory technologies workshop & ERD/ERM working group meeting (April 6–7, 2010). 2010. http://www.itrs.net/Links/2010ITRS/2010Update/ToPost/ERD_ERM_2010FINALReportMemoryAssessment_ITRS.pdf
- Keeney SN: A 130 nm generation high density Etox™ flash memory technology. In Tech Dig - Int Electron Devices Meet2001. Washington, DC; 2001:2.5.1–2.5.4.
- Ray SK, Maikap S, Banerjee W, Das S: Nanocrystals for silicon based light emitting and memory devices. J Phys D Appl Phys 2013, 46: 153001. 10.1088/0022-3727/46/15/153001
- Kato Y, Yamada T, Shimada Y: 0.18-μm nondestructive readout FeRAM using charge compensation technique. IEEE Trans Electron Devices 2005, 52: 2616. 10.1109/TED.2005.859688
- Setter N, Damjanovic D, Eng L, Fox G, Gevorgian S, Hong S, Kingon A, Kohlstedt H, Park NY, Stephenson GB, Stolitchnov I, Taganstev AK, Taylor DV, Yamada T, Streiffer S: Ferroelectric thin films: review of materials, properties, and applications. J Appl Phys 2006, 100: 051606. 10.1063/1.2336999
- Durlam M, Chung Y, DeHerrera M, Engel BN, Grynkewich G, Martino B, Nguyen B, Salter J, Shah P, Slaughter JM: MRAM memory for embedded and stand alone systems. In Proceedings of the IEEE International Conference on Integrated Circuit Design and Technology. Austin; 2007:1–4.
- Sekikawa M, Kiyoyama K, Hasegawa H, Miura K, Fukushima T, Ikeda S, Tanaka T, Ohno H, Koyanagi M: A novel SPRAM (SPin-transfer torque RAM)-based reconfigurable logic block for 3D-stacked reconfigurable spin processor. In Tech Dig - Int Electron Devices Meet. San Francisco, CA; 2008:1–3.
- Raoux S, Burr GW, Breitwisch MJ, Rettner CT, Chen YC, Shelby RM, Salinga M, Krebs D, Chen SH, Lung HL, Lam CH: Phase-change random access memory: a scalable technology. IBM J Res Dev 2008, 52: 465.
- Beck A, Bednorz JG, Gerber C, Rossel C, Widmer D: Reproducible switching effect in thin oxide films for memory applications. Appl Phys Lett 2000, 77: 139. 10.1063/1.126902
- Baek IG, Lee MS, Seo S, Lee MJ, Seo DH, Suh DS, Park JC, Park SO, Kim HS, Yoo IK, Chung UI, Moon JT: Highly scalable non-volatile resistive memory using simple binary oxide driven by asymmetric unipolar voltage pulses. In Tech Dig - Int Electron Devices Meet. San Francisco, CA; 2004:587–590.
- Kozicki MN, Gopalan C, Balakrishnan M, Park M, Mitkova M: Non-volatile memory based on solid electrolytes. In Proceedings 2004 Non-Volatile Memory Technology Symposium. Orlando; 2004:10–17.
- Chen A, Haddad S, Wu YC, Fang TN, Lan Z, Avanzino S, Pangrle S, Buynoski M, Rathor M, Cai W, Tripsas N, Bill C, VanBuskirk M, Taguchi M: Non-volatile resistive switching for advanced memory applications. In Tech Dig - Int Electron Devices Meet. Washington, DC; 2005:746–749.
- Liu CY, Wu PH, Wang A, Jang WY, Young JC, Chiu KY, Tseng TY: Bistable resistive switching of a sputter-deposited Cr-doped SrZrO3 memory film. IEEE Electron Device Lett 2005, 26: 351.
- Waser R, Aono M: Nanoionics-based resistive switching memories. Nat Mater 2007, 6: 833. 10.1038/nmat2023
- Sawa A: Resistive switching in transition metal oxides. Mater Today 2008, 11: 28.
- Lee HY, Chen PS, Wu TY, Chen YS, Wang CC, Tzeng PJ, Lin CH, Chen F, Lien CH, Tsai MJ: Low power and high speed bipolar switching with a thin reactive Ti buffer layer in robust HfO2 based RRAM. In Tech Dig - Int Electron Devices Meet. San Francisco, CA; 2008:1–4.
- Waser R, Dittmann R, Staikov G, Szot K: Redox-based resistive switching memories - nanoionic mechanisms, prospects, and challenges. Adv Mater 2009, 21: 2632. 10.1002/adma.200900375
- Akinaga H, Shima H: Resistive random access memory (ReRAM) based on metal oxides. Proc IEEE 2010, 98: 2237.
- Pan F, Chen C, Wang ZS, Yang YC, Yang J, Zeng F: Nonvolatile resistive switching memories-characteristics, mechanisms and challenges. Proc Natl Acad Sci USA 2010, 20: 1.
- Park J, Lee W, Choe M, Jung S, Son M, Kim S, Park S, Shin J, Lee D, Siddik M, Woo J, Choi G, Cha E, Lee T, Hwang H: Quantized conductive filament formed by limited Cu source in sub-5nm era. In Tech Dig - Int Electron Devices Meet. Washington, DC; 2011:3.7.1–3.7.4.
- Torrezan AC, Strachan JP, Medeiros-Ribeiro G, Williams RS: Sub-nanosecond switching of a tantalum oxide memristor. Nanotechnology 2011, 22: 485203. 10.1088/0957-4484/22/48/485203
- Rahaman SZ, Maikap S, Tien TC, Lee HY, Chen WS, Chen FT, Kao MJ, Tsai MJ: Excellent resistive memory characteristics and switching mechanism using a Ti nanolayer at the Cu/TaO x interface. Nanoscale Res Lett 2012, 7: 345. 10.1186/1556-276X-7-345
- Wong HSP, Lee HY, Yu S, Chen YS, Wu Y, Chen PS, Lee B, Chen FT, Tsai MJ: Metal-oxide RRAM. Proc IEEE 1951, 2012: 100.
- Liu Q, Sun J, Lv H, Long S, Yin K, Wan N, Li Y, Sun L, Liu M: Resistive switching: real-time observation on dynamic growth/dissolution of conductive filaments in oxide-electrolyte-based RERAM. Adv Mater 2012, 24: 1774. 10.1002/adma.201290080
- Yang JJ, Strukov DB, Stewart DR: Memristive devices for computing. Nat Nanotechnol 2013, 8: 13.
- International technology roadmap for semiconductors 2011 edition emerging research devices. http://www.itrs.net/Links/2011itrs/2011Tables/ERD_2011Tables.xlsx
- Burr GW, Kurdi BN, Scott JC, Lam CH, Gopalakrishnan K, Shenoy RS: Overview of candidate device technologies for storage-class memory. IBM J Res Dev 2008, 52: 449.
- Ho C-H, Hsu C-L, Chen C-C, Liu J-T, Wu C-S, Huang C-C, Hu C, Fu-Liang Y: 9 nm half-pitch functional resistive memory cell with <1 μA programming current using thermally oxidized sub-stoichiometric WO x film. In Tech Dig - Int Electron Devices Meet. San Francisco, CA; 2010:19.1.1–19.1.4.
- Lee HY, Chen YS, Chen PS, Gu PY, Hsu YY, Wang SM, Liu WH, Tsai CH, Sheu SS, Chiang PC, Lin WP, Lin CH, Chen WS, Chen FT, Lien CH, Tsai MJ: Evidence and solution of over-RESET problem for HfOx based resistive memory with sub-ns switching speed and high endurance. In Tech Dig - Int Electron Devices Meet. San Francisco, CA; 2010:19.7.1–19.7.4.
- Kim S, Biju KP, Jo M, Jung S, Park J, Lee J, Lee W, Shin J, Park S, Hwang H: Effect of scaling WO x -based RRAMs on their resistive switching characteristics. IEEE Electron Device Lett 2011, 32: 671.
- Lee M-J, Lee CB, Lee D, Lee SR, Chang M, Hur JH, Kim Y-B, Kim C-J, Seo DH, Seo S, Chung UI, Yoo I-K, Kim K: A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O5-x/TaO2-x bilayer structures. Nat Mater 2011, 10: 625. 10.1038/nmat3070
- Hickmott TW: Low-frequency negative resistance in thin anodic oxide films. J Appl Phys 1962, 33: 2669. 10.1063/1.1702530
- Nielsen PH, Bashara NM: The reversible voltage-induced initial resistance in the negative resistance sandwich structure. IEEE Trans Electron Devices 1964, 11: 243.
- Gibbons JF, Beadle WE: Switching properties of thin NiO films. Solid-State Electron 1964, 7: 785. 10.1016/0038-1101(64)90131-5
- Simmons JG, Verderber RR: New conduction and reversible memory phenomena in thin insulating films. Proc R Soc London, Ser A 1967, 301: 77. 10.1098/rspa.1967.0191
- Chua LO: Memristors-the missing circuit element. IEEE Trans Circuit Theory 1971, CT-18: 507.
- Tsuruoka T, Terabe K, Hasegawa T, Aono M: Forming and switching mechanisms of a cation-migration-based oxide resistive memory. Nanotechnology 2010, 21: 425205. 10.1088/0957-4484/21/42/425205
- Chen YS, Lee HY, Chen PS, Wu TY, Wang CC, Tzeng PJ, Chen F, Tsai MJ, Lien C: An ultrathin forming-free HfO x resistance memory with excellent electrical performance. IEEE Electron Device Lett 2010, 31: 1473.
- Qinan M, Zhenguo J, Junhua X: Realization of forming-free ZnO-based resistive switching memory by controlling film thickness. J Phys D Appl Phys 2010, 43: 395104. 10.1088/0022-3727/43/39/395104
- Stille S, Lenser C, Dittmann R, Koehl A, Krug I, Muenstermann R, Perlich J, Schneider CM, Klemradt U, Waser R: Detection of filament formation in forming-free resistive switching SrTiO3 devices with Ti top electrodes. Appl Phys Lett 2012, 100: 223503. 10.1063/1.4724108
- Prakash A, Maikap S, Chiu H-C, Tien T-C, Lai C-S: Enhanced resistive switching memory characteristics and mechanism using a Ti nanolayer at the W/TaO x interface. Nanoscale Res Lett 2013, 8: 288. 10.1186/1556-276X-8-288
- Akinaga H, Shima H, Takano F, Inoue IH, Takagi H: Resistive switching effect in metal/insulator/metal heterostructures and its application for non-volatile memory. IEEJ T Electr 2007, 2: 453.
- Szot K, Speier W, Bihlmayer G, Waser R: Switching the electrical resistance of individual dislocations in single-crystalline SrTiO3. Nat Mater 2006, 5: 312. 10.1038/nmat1614
- Kwon D-H, Kim KM, Jang JH, Jeon JM, Lee MH, Kim GH, Li X-S, Park G-S, Lee B, Han S, Kim M, Hwang CS: Atomic structure of conducting nanofilaments in TiO2 resistive switching memory. Nat Nanotechnol 2010, 5: 148. 10.1038/nnano.2009.456
- Xu Z, Bando Y, Wang W, Bai X, Golberg D: Real-time in situ HRTEM-resolved resistance switching of Ag2S nanoscale ionic conductor. ACS Nano 2010, 4: 2515. 10.1021/nn100483a
- Rahaman SZ, Maikap S, Chen WS, Lee HY, Chen FT, Tien TC, Tsai MJ: Impact of TaO x nanolayer at the GeSe x /W interface on resistive switching memory performance and investigation of Cu nanofilament. J Appl Phys 2012, 111: 063710. 10.1063/1.3696972
- Yang Y, Gao P, Gaba S, Chang T, Pan X, Lu W: Observation of conducting filament growth in nanoscale resistive memories. Nat Commun 2012, 3: 732.
- Rahaman SZ, Maikap S, Chen WS, Lee HY, Chen FT, Kao MJ, Tsai MJ: Repeatable unipolar/bipolar resistive memory characteristics and switching mechanism using a Cu nanofilament in a GeO x film. Appl Phys Lett 2012, 101: 073106. 10.1063/1.4745783
- Jeong HY, Lee JY, Ryu M-K, Choi S-Y: Bipolar resistive switching in amorphous titanium oxide thin film. Phys Status Solidi RRL 2010, 4: 28. 10.1002/pssr.200903383
- Tsui S, Baikalov A, Cmaidalka J, Sun YY, Wang YQ, Xue YY, Chu CW, Chen L, Jacobson AJ: Field-induced resistive switching in metal-oxide interfaces. Appl Phys Lett 2004, 85: 317. 10.1063/1.1768305
- Jeon SH, Park BH, Lee J, Lee B, Han S: First-principles modeling of resistance switching in perovskite oxide material. Appl Phys Lett 2006, 89: 042904. 10.1063/1.2234840
- Seong D-j, Jo M, Lee D, Hwang H: HPHA effect on reversible resistive switching of P/Nb -doped SrTiO3 Schottky junction for nonvolatile memory application. Electrochem Solid-State Lett 2007, 10: H168. 10.1149/1.2718396
- Nian YB, Strozier J, Wu NJ, Chen X, Ignatiev A: Evidence for an oxygen diffusion model for the electric pulse induced resistance change effect in transition-metal oxides. Phys Rev Lett 2007, 98: 146403.
- Sawa A, Fujii T, Kawasaki M, Tokura Y: Hysteretic current–voltage characteristics and resistance switching at a rectifying Ti/Pr0.7Ca0.3MnO3 interface. Appl Phys Lett 2004, 85: 4073. 10.1063/1.1812580
- Fujii T, Kawasaki M, Sawa A, Akoh H, Kawazoe Y, Tokura Y: Hysteretic current–voltage characteristics and resistance switching at an epitaxial oxide Schottky junction SrRuO3/SrTi0.99Nb0.01O3. Appl Phys Lett 2005, 86: 012107. 10.1063/1.1845598
- Rozenberg MJ, Inoue IH, Sánchez MJ: Nonvolatile memory with multilevel switching: a basic model. Phys Rev Lett 2004, 92: 178302.
- Fors R, Khartsev SI, Grishin AM: Giant resistance switching in metal-insulator-manganite junctions: evidence for Mott transition. Phys Rev B 2005, 71: 045305.
- Oka T, Nagaosa N: Interfaces of correlated electron systems: proposed mechanism for colossal electroresistance. Phys Rev Lett 2005, 95: 266403.
- Kund M, Beitel G, Pinnow CU, Röhr T, Schumann J, Symanczyk R, Ufert KD, Müller G: Conductive bridging RAM (CBRAM): an emerging non-volatile memory technology scalable to sub 20 nm. In Tech Dig - Int Electron Devices Meet. Washington, DC; 2005:754–757.
- Rahaman SZ, Maikap S, Das A, Prakash A, Wu YH, Lai CS, Tien TC, Chen WS, Lee HY, Chen FT, Tsai MJ, Chang LB: Enhanced nanoscale resistive switching memory characteristics and switching mechanism using high-Ge-content Ge0.5Se0.5 solid electrolyte. Nanoscale Res Lett 2012, 7: 614. 10.1186/1556-276X-7-614
- Kozicki MN, Balakrishnan M, Gopalan C, Ratnakumar C, Mitkova M: Programmable metallization cell memory based on Ag-Ge-S and Cu-Ge-S solid electrolytes. In 2005 Non-Volatile Memory Technology Symposium. Dallas, TX; 2005:83.
- Jameson JR, Gilbert N, Koushan F, Saenz J, Wang J, Hollmer S, Kozicki M, Derhacobian N: Quantized conductance in Ag/GeS2/W conductive-bridge memory cells. IEEE Electron Device Lett 2012, 33: 257.
- Kaeriyama S, Sakamoto T, Sunamura H, Mizuno M, Kawaura H, Hasegawa T, Terabe K, Nakayama T, Aono M: A nonvolatile programmable solid-electrolyte nanometer switch. IEEE J Solid-State Circuits 2005, 40: 168.
- Terabe K, Hasegawa T, Nakayama T, Aono M: Quantized conductance atomic switch. Nature 2005, 433: 47. 10.1038/nature03190
- Sakamoto T, Lister K, Banno N, Hasegawa T, Terabe K, Aono M: Electronic transport in Ta2O5 resistive switch. Appl Phys Lett 2007, 91: 092110. 10.1063/1.2777170
- Maikap S, Rahaman SZ, Wu TY, Chen FT, Kao MJ, Tsai MJ: Low current (5 pA) resistive switching memory using high-κ Ta2O5 solid electrolyte. In The 39th European Solid-State Device Research Conference and the 35th European Solid-state Circuits Conference (ESSDERC/ESSCIRC). Athens; 2009:217.
- Schindler C, Thermadam SCP, Waser R, Kozicki MN: Bipolar and unipolar resistive switching in Cu-doped SiO2. IEEE Trans Electron Devices 2007, 54: 2762.
- Hsiung CP, Liao HW, Gan JY, Wu TB, Hwang JC, Chen F, Tsai MJ: Formation and instability of silver nanofilament in Ag-based programmable metallization cells. ACS Nano 2010, 4: 5414. 10.1021/nn1010667
- Liu Q, Long S, Lv H, Wang W, Niu J, Huo Z, Chen J, Liu M: Controllable growth of nanoscale conductive filaments in solid-electrolyte-based ReRAM by using a metal nanocrystal covered bottom electrode. ACS Nano 2010, 4: 6162. 10.1021/nn1017582
- Nagata T, Haemori M, Yamashita Y, Yoshikawa H, Iwashita Y, Kobayashi K, Chikyow T: Bias application hard X-ray photoelectron spectroscopy study of forming process of Cu/HfO2/Pt resistive random access memory structure. Appl Phys Lett 2011, 99: 223517. 10.1063/1.3664781
- Yoon J, Choi H, Lee D, Park JB, Lee J, Seong DJ, Ju Y, Chang M, Jung S, Hwang H: Excellent switching uniformity of Cu-doped MoO x /GdO x bilayer for nonvolatile memory applications. IEEE Electron Device Lett 2009, 30: 457.
- Tada M, Sakamoto T, Banno N, Aono M, Hada H, Kasai N: Nonvolatile crossbar switch using TiO x /TaSiO y solid electrolyte. IEEE Trans Electron Devices 1987, 2010: 57.
- Goux L, Opsomer K, Degraeve R, Muller R, Detavernier C, Wouters DJ, Jurczak M, Altimime L, Kittl JA: Influence of the Cu-Te composition and microstructure on the resistive switching of Cu-Te/Al2O3/Si cells. Appl Phys Lett 2011, 99: 053502. 10.1063/1.3621835
- Kim DC, Seo S, Ahn SE, Suh DS, Lee MJ, Park BH, Yoo IK, Baek IG, Kim HJ, Yim EK, Lee JE, Park SO, Kim HS, Chung UI, Moon JT, Ryu BI: Electrical observations of filamentary conductions for the resistive memory switching in NiO films. Appl Phys Lett 2006, 88: 202102. 10.1063/1.2204649
- Ielmini D, Nardi F, Cagli C: Physical models of size-dependent nanofilament formation and rupture in NiO resistive switching memories. Nanotechnology 2011, 22: 254022. 10.1088/0957-4484/22/25/254022
- Jousseaume V, Fantini A, Nodin JF, Guedj C, Persico A, Buckley J, Tirano S, Lorenzi P, Vignon R, Feldis H, Minoret S, Grampeix H, Roule A, Favier S, Martinez E, Calka P, Rochat N, Auvert G, Barnes JP, Gonon P, Vallée C, Perniola L, De Salvo B: Comparative study of non-polar switching behaviors of NiO- and HfO2-based oxide resistive-RAMs. Solid-State Electron 2011, 58: 62. 10.1016/j.sse.2010.11.023
- Yang JJ, Pickett MD, Li X, Ohlberg DAA, Stewart DR, Williams RS: Memristive switching mechanism for metal/oxide/metal nanodevices. Nat Nanotechnol 2008, 3: 429. 10.1038/nnano.2008.160
- Hermes C, Bruchhaus R, Waser R: Forming-free TiO2-based resistive switching devices on CMOS-compatible W-plugs. IEEE Electron Device Lett 2011, 32: 1588.
- Park J, Biju KP, Jung S, Lee W, Lee J, Kim S, Park S, Shin J, Hwang H: Multibit operation of TiO x -based ReRAM by Schottky barrier height engineering. IEEE Electron Device Lett 2011, 32: 476.
- Cheng CH, Chen PC, Wu YH, Yeh FS, Chin A: Long-endurance nanocrystal TiO2 resistive memory using a TaON buffer layer. IEEE Electron Device Lett 2011, 32: 1749.
- Park WY, Kim GH, Seok JY, Kim KM, Song SJ, Lee MH, Hwang CS: A Pt/TiO2/Ti Schottky-type selection diode for alleviating the sneak current in resistance switching memory arrays. Nanotechnology 2010, 21: 195201. 10.1088/0957-4484/21/19/195201
- Lee H-Y, Chen P-S, Wang C-C, Maikap S, Tzeng P-J, Lin C-H, Lee L-S, Tsai M-J: Low-power switching of nonvolatile resistive memory using hafnium oxide. Jpn J Appl Phys, Part 1 2007, 46: 2175. 10.1143/JJAP.46.2175
- Lee J, Bourim EM, Lee W, Park J, Jo M, Jung S, Shin J, Hwang H: Effect of ZrO x /HfO x bilayer structure on switching uniformity and reliability in nonvolatile memory applications. Appl Phys Lett 2010, 97: 172105. 10.1063/1.3491803
- Walczyk D, Walczyk C, Schroeder T, Bertaud T, Sowinska M, Lukosius M, Fraschke M, Tillack B, Wenger C: Resistive switching characteristics of CMOS embedded HfO2-based 1T1R cells. Microelectron Eng 2011, 88: 1133. 10.1016/j.mee.2011.03.123
- Chen YY, Goux L, Clima S, Govoreanu B, Degraeve R, Kar GS, Fantini A, Groeseneken G, Wouters DJ, Jurczak M: Endurance/retention trade-off on HfO2/metal cap 1T1R bipolar RRAM. IEEE Trans Electron Devices 2013, 60: 1114.
- Yu S, Chen H-Y, Gao B, Kang J, Wong HSP: HfO x -based vertical resistive switching random access memory suitable for bit-cost-effective three-dimensional cross-point architecture. ACS Nano 2013, 7: 2320. 10.1021/nn305510u
- Chen A, Haddad S, Wu YC, Fang TN, Kaza S, Lan Z: Erasing characteristics of Cu2O metal-insulator-metal resistive switching memory. Appl Phys Lett 2008, 92: 013503. 10.1063/1.2828864
- Sun X, Li G, Chen L, Shi Z, Zhang W: Bipolar resistance switching characteristics with opposite polarity of Au/SrTiO3/Ti memory cells. Nanoscale Res Lett 2011, 6: 1.
- Lin CY, Wu CY, Wu CYC-Y, Lee TC, Yang FL, Hu C, Tseng TY: Effect of top electrode material on resistive switching properties of ZrO2 film memory devices. IEEE Electron Device Lett 2007, 28: 366.
- Liu Q, Long S, Wang W, Zuo Q, Zhang S, Chen J, Liu M: Improvement of resistive switching properties in ZrO2-based ReRAM with implanted Ti ions. IEEE Electron Device Lett 2009, 30: 1335.
- Wang S-Y, Lee D-Y, Tseng T-Y, Lin C-Y: Effects of Ti top electrode thickness on the resistive switching behaviors of rf-sputtered ZrO2 memory films. Appl Phys Lett 2009, 95: 112904. 10.1063/1.3231872
- Wang SY, Lee DY, Huang TY, Wu JW, Tseng TY: Controllable oxygen vacancies to enhance resistive switching performance in a ZrO2-based RRAM with embedded Mo layer. Nanotechnology 2010, 21: 495201. 10.1088/0957-4484/21/49/495201
- Chien WC, Chen YC, Lai EK, Yao YD, Lin P, Horng SF, Gong J, Chou TH, Lin HM, Chang MN, Shih YH, Hsieh KY, Liu R, Chih-Yuan L: Unipolar switching behaviors of RTO WO x RRAM. IEEE Electron Device Lett 2010, 31: 126.
- Lin CY, Wu CY, Hu C, Tseng TY: Bistable resistive switching in Al2O3 memory thin films. J Electrochem Soc 2007, 154: G189. 10.1149/1.2750450
- Banerjee W, Rahaman SZ, Prakash A, Maikap S: High-κ Al2O3/WO x bilayer dielectrics for low-power resistive switching memory applications. Jpn J Appl Phys 2011, 50: 10PH01. 10.1143/JJAP.50.10PH01
- Wu Y, Yu S, Lee B, Wong HSP: Low-power TiN/Al2O3/Pt resistive switching device with sub-20 μA switching current and gradual resistance modulation. J Appl Phys 2011, 110: 094104. 10.1063/1.3657938
- Banerjee W, Maikap S, Rahaman SZ, Prakash A, Tien TC, Li WC, Yang JR: Improved resistive switching memory characteristics using core-shell IrO x nano-dots in Al2O3/WO x bilayer structure. J Electrochem Soc 2012, 159: H177. 10.1149/2.067202jes
- Peng HY, Li GP, Ye JY, Wei ZP, Zhang Z, Wang DD, Xing GZ, Wu T: Electrode dependence of resistive switching in Mn-doped ZnO: filamentary versus interfacial mechanisms. Appl Phys Lett 2010, 96: 192113. 10.1063/1.3428365
- Andy S, Wendi Z, Julia Q, Han-Jen Y, Shuyi C, Zetian M, Ishiang S: Highly stable resistive switching on monocrystalline ZnO. Nanotechnology 2010, 21: 125201. 10.1088/0957-4484/21/12/125201
- Chiu FC, Li PW, Chang WY: Reliability characteristics and conduction mechanisms in resistive switching memory devices using ZnO thin films. Nanoscale Res Lett 2012, 7: 1. 10.1186/1556-276X-7-1
- Peng CN, Wang CW, Chan TC, Chang WY, Wang YC, Tsai HW, Wu WW, Chen LJ, Chueh YL: Resistive switching of Au/ZnO/Au resistive memory: an in situ observation of conductive bridge formation. Nanoscale Res Lett 2012, 7: 1. 10.1186/1556-276X-7-1
- Yao J, Zhong L, Natelson D, Tour JM: Intrinsic resistive switching and memory effects in silicon oxide. Appl Phys A 2011, 102: 835. 10.1007/s00339-011-6267-6
- Mehonic A, Cueff S, Wojdak M, Hudziak S, Jambois O, Labbe C, Garrido B, Rizk R, Kenyon AJ: Resistive switching in silicon suboxide films. J Appl Phys 2012, 111: 074507. 10.1063/1.3701581
- Cao X, Li X, Gao X, Yu W, Liu X, Zhang Y, Chen L, Cheng X: Forming-free colossal resistive switching effect in rare-earth-oxide Gd2O3 films for memristor applications. J Appl Phys 2009, 106: 073723. 10.1063/1.3236573
- Jana D, Maikap S, Tien TC, Lee HY, Chen WS, Chen FT, Kao MJ, Tsai MJ: Formation-polarity-dependent improved resistive switching memory performance using IrO x /GdO x /WO x /W structure. Jpn J Appl Phys 2012, 51: 04DD17.
- Seong DJ, Hassan M, Choi H, Lee J, Yoon J, Park JB, Lee W, Oh MS, Hwang H: Resistive-switching characteristics of Al/Pr0.7Ca0.3MnO3 for nonvolatile memory applications. IEEE Electron Device Lett 2009, 30: 919.
- Cheng CH, Chin A, Yeh FS: Ultralow switching energy Ni/GeO x /HfON/TaN RRAM. IEEE Electron Device Lett 2011, 32: 366.
- Prakash A, Maikap S, Rahaman S, Majumdar S, Manna S, Ray S: Resistive switching memory characteristics of Ge/GeO x nanowires and evidence of oxygen ion migration. Nanoscale Res Lett 2013, 8: 220. 10.1186/1556-276X-8-220
- Wei Z, Kanzawa Y, Arita K, Katoh Y, Kawai K, Muraoka S, Mitani S, Fujii S, Katayama K, Iijima M, Mikawa T, Ninomiya T, Miyanaga R, Kawashima Y, Tsuji K, Himeno A, Okada T, Azuma R, Shimakawa K, Sugaya H, Takagi T, Yasuhara R, Khoriba G, Kumigashira H, Oshima M: Highly reliable TaO x ReRAM and direct evidence of redox reaction mechanism. In Tech Dig - Int Electron Devices Meet. San Francisco, CA; 2008:1–4.
- Yang JJ, Zhang MX, Strachan JP, Miao F, Pickett MD, Kelley RD, Medeiros-Ribeiro G, Williams RS: High switching endurance in TaO x memristive devices. Appl Phys Lett 2010, 97: 232102. 10.1063/1.3524521
- Zhang L, Huang R, Zhu M, Qin S, Kuang Y, Gao D, Shi C, Wang Y: Unipolar TaO x -based resistive change memory realized with electrode engineering. IEEE Electron Device Lett 2010, 31: 966.
- Gu T, Tada T, Watanabe S: Conductive path formation in the Ta2O5 atomic switch: first-principles analyses. ACS Nano 2010, 4: 6477. 10.1021/nn101410s
- Wei Z, Takagi T, Kanzawa Y, Katoh Y, Ninomiya T, Kawai K, Muraoka S, Mitani S, Katayama K, Fujii S, Miyanaga R, Kawashima Y, Mikawa T, Shimakawa K, Aono K: Demonstration of high-density ReRAM ensuring 10-year retention at 85°C based on a newly developed reliability model. In Tech Dig - Int Electron Devices Meet. Washington, DC; 2011:31.4.1–31.4.4.
- Prakash A, Maikap S, Lai CS, Tien TC, Chen WS, Lee HY, Chen FT, Kao MJ, Tsai MJ: Bipolar resistive switching memory using bilayer TaO x /WO x films. Solid-State Electron 2012, 77: 35.
- Chen C, Song C, Yang J, Zeng F, Pan F: Oxygen migration induced resistive switching effect and its thermal stability in W/TaO x /Pt structure. Appl Phys Lett 2012, 100: 253509. 10.1063/1.4730601
- Prakash A, Maikap S, Lai CS, Lee HY, Chen WS, Chen FT, Kao MJ, Tsai MJ: Improvement of uniformity of resistive switching parameters by selecting the electroformation polarity in IrO x /TaO x /WO x /W structure. Jpn J Appl Phys, Part 1 2012, 51: 04DD06.
- Yang Y, Sheridan P, Lu W: Complementary resistive switching in tantalum oxide-based resistive memory devices. Appl Phys Lett 2012, 100: 203112. 10.1063/1.4719198
- Bishop SM, Bakhru H, Capulong JO, Cady NC: Influence of the SET current on the resistive switching properties of tantalum oxide created by oxygen implantation. Appl Phys Lett 2012, 100: 142111. 10.1063/1.3701154
- Marinella MJ, Dalton SM, Mickel PR, Dodd PED, Shaneyfelt MR, Bielejec E, Vizkelethy G, Kotula PG: Initial assessment of the effects of radiation on the electrical characteristics of TaO x memristive memories. IEEE Trans Nucl Sci 2012, 59: 2987.
- Ninomiya T, Wei Z, Muraoka S, Yasuhara R, Katayama K, Takagi T: Conductive filament scaling of TaO x bipolar ReRAM for improving data retention under low operation current. IEEE Trans Electron Devices 2013, 60: 1384.
- Diokh T, Le-Roux E, Jeannot S, Cagli C, Jousseaume V, Nodin J-F, Gros-Jean M, Gaumer C, Mellier M, Cluzel J, Carabasse C, Candelier P, De Salvo B: Study of resistive random access memory based on TiN/TaO x /TiN integrated into a 65 nm advanced complementary metal oxide semiconductor technology. Thin Solid Films 2013, 533: 24.
- Mickel PR, Lohn AJ, Choi BJ, Yang JJ, Zhang M-X, Marinella MJ, James CD, Williams RS: A physical model of switching dynamics in tantalum oxide memristive devices. Appl Phys Lett 2013, 102: 223502. 10.1063/1.4809530
- Schmelzer S, Linn E, Bottger U, Waser R: Uniform complementary resistive switching in tantalum oxide using current sweeps. IEEE Electron Device Lett 2013, 34: 114.
- Lee D, Woo J, Cha E, Kim S, Lee W, Park S, Hwang H: Interface engineering for low power and uniform resistive switching in bi-layer structural filament type ReRAM. Microelectron Eng 2013, 109: 385.
- Kim S, Kim S-J, Kim KM, Lee SR, Chang M, Cho E, Kim Y-B, Kim CJ, In Chung U: Physical electro-thermal model of resistive switching in bi-layered resistance-change memory. Sci Rep 2013, 3: 1.
- Zhuo VYQ, Jiang Y, Li MH, Chua EK, Zhang Z, Pan JS, Zhao R, Shi LP, Chong TC, Robertson J: Band alignment between Ta2O5 and metals for resistive random access memory electrodes engineering. Appl Phys Lett 2013, 102: 062106. 10.1063/1.4792274
- Elliman RG, Saleh MS, Kim TH, Venkatachalam DK, Belay K, Ruffell S, Kurunczi P, England J: Application of ion-implantation for improved non-volatile resistive random access memory (ReRAM). Nucl Instrum Methods Phys Res, Sect B 2013, 307: 98.
- Yang Y, Choi S, Lu W: Oxide heterostructure resistive memory. Nano Lett 2013, 13: 2908. 10.1021/nl401287w
- Garg SP, Krishnamurthy N, Awasthi A, Venkatraman M: The O-Ta (oxygen-tantalum) system. J Phase Equil 1996, 17: 63. 10.1007/BF02648373
- Birks N, Meier GH, Pettit FS: Introduction to the high-temperature oxidation of metals. Cambridge: Cambridge University Press; 2006. http://www.doitpoms.ac.uk/tlplib/ellingham_diagrams/interactive.php
- Fujimoto M, Koyama H, Konagai M, Hosoi Y, Ishihara K, Ohnishi S, Awaya N: TiO2 anatase nanolayer on TiN thin film exhibiting high-speed bipolar resistive switching. Appl Phys Lett 2006, 89: 223509. 10.1063/1.2397006
- Hur JH, Lee M-J, Lee CB, Kim Y-B, Kim C-J: Modeling for bipolar resistive memory switching in transition-metal oxides. Phys Rev B 2010, 82: 155321.
- Yoshida C, Kinoshita K, Yamasaki T, Sugiyama Y: Direct observation of oxygen movement during resistance switching in NiO/Pt film. Appl Phys Lett 2008, 93: 042106. 10.1063/1.2966141
- Linn E, Rosezin R, Kugeler C, Waser R: Complementary resistive switches for passive nanocrossbar memories. Nat Mater 2010, 9: 403. 10.1038/nmat2748
- Long S, Lian X, Cagli C, Cartoix X, Rurali R, Miranda E, Jimenez D, Perniola L, Ming Liu M, Sune J: Quantum-size effects in hafnium-oxide resistive switching. Appl Phys Lett 2013, 102: 183505. 10.1063/1.4802265
- Long S, Cagli C, Ielmini D, Liu M, Sune J: Analysis and modeling of resistive switching statistics. J Appl Phys 2012, 111: 074508. 10.1063/1.3699369
- Terai M, Sakotsubo Y, Saito Y, Kotsuji S, Hada H: Effect of bottom electrode of ReRAM with Ta2O5/TiO2 stack on RTN and retention. In Tech Dig - Int Electron Devices Meet. Baltimore, MD; 2009:1–4.
- Chen YS, Lee HY, Chen PS, Liu WH, Wang SM, Gu PY, Hsu YY, Tsai CH, Chen WS, Chen F, Tsai MJ, Lien C: Robust high-resistance state and improved endurance of HfO x resistive memory by suppression of current overshoot. IEEE Electron Device Lett 2011, 32: 1585.
- Govoreanu B, Kar GS, Chen Y, Paraschiv V, Kubicek S, Fantini A, Radu IP, Goux L, Clima S, Degraeve R, Jossart N, Richard O, Vandeweyer T, Seo K, Hendrickx P, Pourtois G, Bender H, Altimime L, Wouters DJ, Kittl JA, Jurczak M: 10 × 10nm2 Hf/HfO x crossbar resistive RAM with excellent performance, reliability and low-energy operation. In Tech Dig - Int Electron Devices Meet. Washington, DC; 2011:31.6.1–31.6.4.
- Chien WC, Chen YR, Chen YC, Chuang ATH, Lee FM, Lin YY, Lai EK, Shih YH, Hsieh KY, Chih-Yuan L: A forming-free WO x resistive memory using a novel self-aligned field enhancement feature with excellent reliability and scalability. In Tech Dig - Int Electron Devices Meet. San Francisco, CA; 2010:19.2.1–19.2.4.
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