Abstract
Enhanced resistive switching phenomena of IrO x /GdO x /W cross-point memory devices have been observed as compared to the via-hole devices. The as-deposited Gd2O3 films with a thickness of approximately 15 nm show polycrystalline that is observed using high-resolution transmission electron microscope. Via-hole memory device shows bipolar resistive switching phenomena with a large formation voltage of -6.4 V and high operation current of >1 mA, while the cross-point memory device shows also bipolar resistive switching with low-voltage format of +2 V and self-compliance operation current of <300 μA. Switching mechanism is based on the formation and rupture of conducting filament at the IrO x /GdO x interface, owing to oxygen ion migration. The oxygen-rich GdO x layer formation at the IrO x /GdO x interface will also help control the resistive switching characteristics. This cross-point memory device has also Repeatable 100 DC switching cycles, narrow distribution of LRS/HRS, excellent pulse endurance of >10,000 in every cycle, and good data retention of >104 s. This memory device has great potential for future nanoscale high-density non-volatile memory applications.
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Background
There is an increasing demand for next-generation high-density non-volatile memory devices because flash memories are approaching their scaling limits. Among many candidates to replace the flash memory devices, resistive random access memory (RRAM) is one of the promising candidates, owing to its simple metal-insulator-metal structure, fast switching speed, low-power operation, excellent scalability potential, and high density in crossbar structure [1–4]. Many switching materials such as TaO x [5–7], AlO x [8, 9], HfO x [10–15], TiO x [16, 17], NiO x [18–21], WO x [22, 23], ZnO x [24, 25], ZrO x [26–31], SrTiO3 [32, 33], SiO x [34, 35], and Pr0.7Ca0.3MnO3 [36, 37] have been studied by several groups. However, the rare-earth oxide such as Gd2O3 could be a promising resistive switching material because of its high resistivity, high dielectric permittivity (κ = 16), moderate energy gap (Eg = approximately 5.3 eV), and higher thermodynamic stability [38]. Recently, many researchers have reported the resistive switching properties by using Gd2O3 materials [38–40]. Cao et al. [38] have reported unipolar resistive switching phenomena using Pt/Gd2O3/Pt structure with a high RESET current of 35 mA. Liu et al. [39] have also reported unipolar resistive switching phenomena with a high RESET current of 10 mA in Ti/Gd2O3/Pt structure. Yoon et al. [40] have reported resistive switching characteristics using MoO x /GdO x bilayer structure with a RESET current of 300 μA. It is found that non-uniform switching and high overshoot current are the main drawbacks for practical application of non-volatile RRAM using Gd2O3 material. Even though many structures using the Gd2O3 materials have been reported, however, the cross-point memory devices using IrO x /GdO x /W structure have not yet been reported. It is reported [41] that the cross-point structure has a great potential for high-density memory application in the near future.
In this study, we discussed resistive switching phenomena of IrO x /GdO x /W cross-point memory structure. For comparison, the IrO x /GdO x /W via-hole structure has been also investigated. The IrO x /GdO x /W via-hole memory devices exhibit negative switching polarity, whereas the IrO x /GdO x /W cross-point memory devices show positive switching polarity. Switching non-uniformity and high operation voltage/current of the via-hole devices are observed. To improve the switching uniformity and control the current overshoot, we have designed the IrO x /GdO x /W cross-point memory devices. In the cross-point structure, IrO x /GdO x /W memory device shows stable and uniform positive switching due to the formation of oxygen-rich interfacial layer at the IrO x /GdO x interface. The cross-point memory device has self-compliance bipolar resistive switching phenomena of consecutive 100 cycles with narrow distribution of high resistance state (HRS), low resistance state (LRS), good device-to-device uniformity, excellent P/E cycles of >10,000, and good data retention with resistance ratio of 100 after 104 s under a low operation voltage of ±3.5 V.
Methods
First, the cross-point memory devices using the IrO x /GdO x /W structure were fabricated. After conventional RCA cleaning of p-type Si wafer, 200-nm-thick SiO2 was grown by wet oxidation process. Then, a tungsten (W) metal layer of approximately 200 nm was deposited on the SiO2/Si substrate by radio frequency (rf) sputtering process. The deposition power was 150 W, and argon (Ar) with flow rate of 25 sccm was used. The W bars with different widths of 4 to 50 μm were patterned by optical lithography and wet etching process, which serve as bottom electrode (BE). Another lithography process step was used to obtain top electrode bar (TE) by lift-off. The high-κ Gd2O3 as a switching material was deposited by electron beam evaporation. The thickness of the Gd2O3 film was approximately 15 nm. Pure Gd2O3 shots with granules sizes of 2 to 3 mm were used. The deposition rate of Gd2O3 was 0.2 Å/s, and the power was 400 W. Then, iridium-oxide (IrO x ) as a TE with a thickness of approximately 200 nm was deposited by rf sputtering. An iridium (Ir) target was used for the IrO x TE. The ratio of Ar to O gases was 1:1 (i.e., 25/25 sccm). The deposition power and chamber pressure were 50 W and 20 mTorr, respectively. The Ir bars with different widths of 4 to 50 μm were laid 90° with W BEs. Finally, lift-off was performed to get the final devices with different sizes of 4 × 4 to 50 × 50 μm2. Then, the device was annealed at 400°C in N2 ambient for 10 min. The N2 pressure was 5 SLM. The cross-point memories with different arrays of 1 × 1 to 10 × 10 were designed, and the memory device at the 1 × 1 position was measured in this study. Figure 1 shows a schematic view of our IrO x /GdO x /W cross-point memory device. Figure 2 shows the topography of the Gd2O3 and IrO x films, observed using atomic force microscope (AFM). AFM images of two-dimensional (2D) format are shown in Figure 2a,c, and three-dimensional (3D) images are shown in Figure 2b,d. The root mean square (rms, Rq) and average (Ra) surface roughness are found to be 0.688 and 0.518 nm of the Gd2O3 film on Si substrate, while those values are found to be 1.29 and 1.03 nm of the IrO x film on Gd2O3/SiO2/Si substrate, respectively. For comparison, we have also studied the surface roughness of W BE for the via-hole and cross-point memory devices. The root mean square (Rq) surface roughness of W BE for the via-hole and cross-point devices is found to be 1.35 and 4.21 nm, and the average surface roughness (Ra) is found to be 1.05 and 3.35 nm, respectively [42]. It is observed that the surface roughness of W BE is higher than those of GdO x and IrO x , which might have great impact on W BE as well as improved resistive switching characteristics.
Second, the via-hole devices were fabricated for comparison. The fabrication steps are as follows. The W metal as a BE was deposited by rf sputtering on SiO2 (200 nm)/Si wafers. In this device, the thickness of W layer was approximately 100 nm. To form the RRAM device, the SiO2 layer with a thickness of approximately 150 nm was deposited. Then, a small via-hole with an active area of 2 × 2 μm2 was designed using standard lithography. Photoresist (PR) was used to design the pattern and was opened at the active and TE regions. Then, the Gd2O3 film with a thickness of 15 nm was deposited. Finally, lift-off was performed to get the memory device. A schematic view of our IrO x /GdO x /W via-hole structure is shown in Figure 3. During electrical measurement of the memory devices, the BE was grounded and the sweeping bias was applied on the TE.
Results and discussion
Figure 4a shows the HRTEM image of our memory device for the as-deposited Gd2O3 film. Each layer is shown. The thickness of the GdO x layer is approximately 15 nm. To identify the crystalline nature of the Gd2O3 film, the calculated d spacings are found to be 2.78 Å (101), 2.91 Å (002), and 3.06 Å (100), which are similar (2.69 Å (200), 3.09 Å (111), and 1.89 Å (220)) to those reported in the literature [43]. This suggests that this as-deposited Gd2O3 film is polycrystalline. The energy diffraction X-ray spectroscopy (EDX) spectra confirm the presence of expected elements Ir, Gd, W, and O in respective layers, as shown in Figure 4b. The X-ray photoelectron spectroscopy (XPS) spectra of Gd 3d5/2 and Gd2O3 3d5/2 peaks are located at 1,186.73 and 1,189 eV, respectively (Figure 5), which proves a Gd-rich Gd2O3 film, i.e., GdO x . The height ratio of Gd/Gd2O3 is 1:0.93, and area ratio of Gd/Gd2O3 is 1:0.89. Arhen et al. [44] reported the same chemical bonding states at 1,186 and 1,188 eV for the Gd 3d5/2 and Gd2O3 3d5/2 peaks, respectively. This suggests that the as-deposited Gd2O3 film is a Gd-rich GdO x film. It is known that the grain boundary has more defects or weak Gd-O bonds. This suggests that the Gd-O bonds will break easily under external bias, and more oxygen vacancies will be created. The conducting filament will be formed through the grain boundaries. However, the nanotips on the W BE will help the structure have repeatable resistive switching memory characteristics.
Figure 6a shows the typical current–voltage (I-V) characteristics of a IrO x /GdO x /W RRAM device in via-hole structure, as illustrated schematically in Figure 3. The pristine device shows very low leakage current (arrow 1). In order to activate the resistive switching, an initial soft breakdown process (forming) was carried out by applying negative bias on the TE. The negative forming voltage (Vform) is -6.4 V to initiate the resistive switching with a current compliance (CC) of 100 μA. During the formation process, the Gd-O bonds break, which creates oxygen vacancy as well as oxygen vacancy filament, and set LRS. In consequence, the oxygen ions (O2–) will be migrated toward the W BE and react partially at the BE. Bipolar I-V characteristics are indicated by arrows 2 to 4. The SET (VSET) and RESET voltages (VRESET) are found to be -2.2 and +2 V, respectively. To elucidate the conduction mechanism of the IrO x /GdO x /W memory device, the I-V curves are plotted in log-log scale, as shown in Figure 6b. Both LRS and HRS show ohmic conduction behaviors with a slope approximately 1.1. The LRS is ohmic because of the conducting filament formation in the GdO x layer. The HRS is also ohmic because the electrons move through the defects of the GdO x grain boundary. The ohmic behavior of the HRS was also reported by Jung et al. [45]. The resistive switching mechanism can be explained as follows. When negative bias is applied on the TE, the oxygen ions will move from the GdO x layer to the WO x layer. Then, the oxygen vacancy filament will form in the GdO x layer, and the device switches to LRS, which is shown schematically in Figure 6c. The conducting filament will be ruptured by applying positive bias on the TE, and the device switches to HRS, as shown in Figure 6d. In this case, the O2– ions will move from the WO x layer toward the GdO x layer and oxidize the conducting filament. Basically, the conducting filament formation/rupture is due to the oxygen ion migration. This via-hole memory device has read pulse endurance of >105 cycles and good data retention at 85°C (not shown here). Both the LRS and HRS with a high resistance ratio of >103 can be retained after 104 s at 85°C. It is indicating that the memory device is non-volatile and stable at 85°C. However, this device operation current is high (>1 mA), and the I-V switching cycles has variation. This indicates that the via-hole device in an IrO x /GdO x /W structure needs high current operation and that multiple conducting filaments could be formed, which is difficult to control the repeatable switching, and it is also against the future application of nanoscale non-volatile memory. To resolve this issue, we have fabricated the cross-point memory device using the same IrO x /GdO x /W structure, and the improved memory characteristics are observed below.
Figure 7a shows self-compliance bipolar current–voltage characteristics of our cross-point memory device. Initially, the memory device was in HRS or initial resistance state (IRS). Therefore, the first switching cycle of the memory device shows like formation with small forming voltage (Vform) +2 V, which is comparatively very lower than the via-hole device (-6.4 V) as shown in Figure 6a. This suggests that extra forming step is not required in our cross-point device if it is operated within ±3 V, which is very useful for practical realization because of its cost effectiveness and reduction of circuit complexity. The cross-point memory device exhibits Repeatable 100 cycles with small operating voltage of ±3 V, has a low-positive-voltage format, and has a self-compliance with a low current approximately 300 μA at a voltage of ±2 V. Both SET and RESET currents are almost the same, which indicates a good current clamping between the TE and BE in the switching material. To identify the current conduction mechanism, the I-V curve was fitted in the log-log scale, as shown in Figure 7b. The slope values of LRS are 1.3 (I αV1.3) and 1.9 (I αV1.9) at low- and high-voltage regions, respectively, whereas the slope values of HRS are 2.3 (I αV2.3) and 4.3 (I αV4.3) at low- and high-voltage regions, respectively. This suggests that the conduction mechanism for both LRS and HRS is trap-controlled space charge-limited current conduction mechanism (TC-SCLC). The switching mechanism is based on the formation and rupture of the conducting filament at the IrO x (TE)/GdO x interface, depending upon the electrical bias. By applying negative bias on the TE of the IrO x /GdO x /W via-hole devices, the O2– ions drift toward the W BE and partially oxidize, as well as sink into the W BE. Due to the presence of huge numbers of oxygen vacancies into the GdO x layer, there is much possibility to form multiple filaments resulting in non-uniform resistive switching. This phenomenon was also observed for IrO x /TaO x /W structure [46]. By applying positive bias on the IrO x /GdO x /W via-hole devices, the O2– ions migrate toward the IrO x TE. Due to the porous nature of IrO x , some O2– ions drift out and some oxygen are gathered at the IrO x /GdO x interface. The porous IrO x film was also reported recently [47]. Oxygen-rich GdO x layer at the GdO x /TE interface acts as a series resistance which restricts the overshoot current and makes the filament uniform. This interfacial series resistance helps achieve a repeatable switching cycle; however, few devices are controllable. On the other hand, a cross-point memory device does not exhibit switching under negative bias on the IrO x TE, owing to higher resistivity of thinner IrO x TE, and the device cannot reach a higher operating current. However, the cross-point memory device exhibits excellent resistive switching characteristics under positive bias on the IrO x TE due to both the rough surface of the W BE and oxygen gathering at the IrO x /GdO x interface. The electric field enhancement on the nanotips of the W BE and the interfacial series resistance of IrO x /GdO x with thinner layer IrO x TE help the structure have controllable resistive switching characteristics. Owing to the structural shape and the W BE surface differences, the cross-point memory devices have low-positive-voltage format, repeatable switching cycles, and self-compliance, and have improved switching characteristics than the via-hole devices. The similar phenomena was also reported recently [48]. However, further study is ongoing to understand the different resistive switching characteristics between the via-hole and cross-point memory devices. To check the uniformity of the cross-point memory devices, the statistical distribution of IRS, HRS, and LRS were randomly measured in more than 20 devices, as shown in Figure 8. Some devices are not switchable, which may be due to process variation from our deposition system. Most of the memory devices exhibit good distribution of IRS, HRS, and LRS. The average values (σm) of IRS, HRS, and LRS are found to be 29.44G Ω, 9.57 MΩ, and 14.87 kΩ, and those values for standard deviation (σs) are 89.47, 7.21, and 6.67, respectively. This suggests that the memory device has great potential for high-density memory application. Excellent program/erase (P/E) of >10,000 cycles is manifested in our IrO x /GdO x /W cross-point memory device, as shown in Figure 9a. Every cycle was measured during the measurement. The program and erase voltages were +3.5 and -2.5 V, respectively, as shown schematically in the inset of Figure 9a. After 104 P/E cycles, the memory device maintain a resistance ratio of approximately 10 which is also acceptable for multilevel cell operation. Good data retention of >104 s is observed, as shown in Figure 9b. Both HRS and LRS were read out at +0.2 V. A large resistance ratio of approximately 100 is maintained after 104 s. This cross-point memory device paves a way in future nanoscale high-density non-volatile memory.
Conclusions
Enhanced resistive switching characteristics using the IrO x /GdO x /W cross-point memory structure have been obtained. The HRTEM image shows a polycrystalline structure of the GdO x films. The switching mechanism is based on the formation and rupture of the conducting filament by oxygen ion migration, and the oxygen-rich GdO x layer formation at the IrO x /GdO x interface acts as a series resistance to control the current overshoot effect and improves the switching uniformity as compared to the via-hole devices. The cross-point memory device shows self-compliance bipolar resistive switching phenomena of consecutive 100 cycles with narrow distribution of LRS and HRS, excellent P/E cycles of >10,000, and good data retention of >104 s with resistance ratio >102 under low operation voltage of ±3 V. This memory device paves a way for future nanoscale high-density non-volatile memory applications.
Authors’ information
DJ is a Ph.D. student since September 2010, and AP has received his Ph.D. degree on July 2013 under the instruction of Professor SM. SM has been an Associate Professor in the Department of Electronic Engineering, Chang Gung University since August 2009. YYC is a Ph.D. student in the Department of Materials Science and Engineering, National Taiwan University, under the instruction of Professor JRY. HCC has been a Professor in the Department of Electronic Engineering, Chang Gung University since August 2010.
References
Waser R, Aono M: Nanoionics-based resistive switching memories. Nat Mater 2007, 6: 833. 10.1038/nmat2023
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. Piscataway: IEEE: Technical Digest IEEE International Electron Devices Meeting. Edited by IEEE; 2010:460.
Ho CH, Hsu CL, Chen CC, Liu JT, Wu CS, Huang CC, Hu C, Fu-Liang Y: 9nm half-pitch functional resistive memory cell with <1 μA programming current using thermally oxidized sub-stoichiometric WOx film. Piscataway: IEEE: Technical Digest IEEE International Electron Devices Meeting. Edited by IEEE; 2010:436.
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. Piscataway: IEEE: Technical Digest IEEE International Electron Devices Meeting. Edited by IEEE; 2011:63.
Prakash A, Jana D, Maikap S: TaO x -based resistive switching memories: prospective and challenges. Nano Res Lett 2013, 8: 418. 10.1186/1556-276X-8-418
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
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
Wu Y, Yu S, Lee B, Wong P: 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
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.
Lee HY, Chen PS, Wang CC, Maikap S, Tzeng PJ, Lin CH, Lee LS, Tsai MJ: Low-power switching of nonvolatile resistive memory using hafnium oxide. Jpn J Appl Phys Part 1 2007, 46: 2175. 10.1143/JJAP.46.2175
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.
Long S, Lian X, Cagli C, Cartoixá X, Rurali R, Miranda E, Jiménez D, Perniola L, Liu M, Suñé J: Quantum-size effects in hafnium-oxide resistive switching. Appl Phys Lett 2013, 102: 183505. 10.1063/1.4802265
Long S, Perniola L, Cagli C, Buckley J, Lian X, Miranda E, Pan F, Liu M, Suñé J: Voltage and power-controlled regimes in the progressive unipolar RESET transition of HfO2-based RRAM. Sci Rep 2013, 3: 2929.
Long S, Lian X, Cagli C, Perniola L, Miranda E, Liu M, Suñé J: A model for the set statistics of RRAM inspired in the percolation model of oxide breakdown. IEEE Electron Device Lett 2010, 34: 999.
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.
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
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
Panda D, Huang CY, Tseng TY: Resistive switching characteristics of nickel silicide layer embedded HfO2 film. Appl Phys Lett 2012, 100: 112901. 10.1063/1.3694045
Long S, Cagli C, Ielmini D, Liu M, Suñé J: Reset statistics of NiO-based resistive switching memories. IEEE Electron Device Lett 2011, 32: 1570.
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.
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.
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
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
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.
Lin CC, Chang YP, Lin HB, Lin CH: Effect of non-lattice oxygen on ZrO2-based resistive switching memory. Nanoscale Research Lett 2012, 7: 187. 10.1186/1556-276X-7-187
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.
Liu Q, Guan W, Long S, Jia R, Liu M: Resistive switching memory effect of ZrO2 films with Zr+ implanted. Appl Phys Lett 2008, 92: 012117. 10.1063/1.2832660
Guan W, Long S, Liu Q, Liu M, Wang W: Nonpolar nonvolatile resistive switching in Cu-doped ZrO2. IEEE Electron Device Lett 2008, 29: 434.
Guan W, Long S, Jia R, Liu M: Nonvolatile resistive switching memory utilizing gold nanocrystals embedded in zirconium oxide. Appl Phys Lett 2007, 91: 062111. 10.1063/1.2760156
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
Sun X, Li G, Chen L, Shi Z, Zhang W: Bipolar resistance switching characteristics with opposite polarity of Au/SrTiO3/Ti memory cell. Nano Res Lett 2011, 6: 599. 10.1186/1556-276X-6-599
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
Liu CY, Huang JJ, Lai CH, Lin CH: Influence of embedding Cu nano-particles into a Cu/SiO2/Pt structure on its resistive switching. Nano Res Lett 2013, 8: 156. 10.1186/1556-276X-8-156
Sawa A: Resistive switching in transition metal oxides. Mater Today 2008, 11: 28.
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 Let 2009, 30: 919.
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
Liu KC, Tzeng WH, Chang KM, Chan YC, Kuo CC, Cheng CW: The resistive switching characteristics of a Ti/Gd2O3/Pt RRAM device. Microelectron Reliab 2010, 50: 670. 10.1016/j.microrel.2010.02.006
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 application. IEEE Electron Device Lett 2009, 30: 457.
Kim KH, Gaba S, Wheeler D, Cruz-Albrecht JM, Hussain T, Srinivasa N, Lu W: A functional hybrid memristor crossbar-array/CMOS system for data storage and neuromorphic applications. Nano Lett 2011, 12: 389.
Prakash A, Jana D, Samanta S, Maikap S: Self-compliance improved resistive switching using Ir/TaO x /W cross-point memory. Nano Res Lett 2013, 8: 527. 10.1186/1556-276X-8-527
Cho HK, Cho HJ, Lone S, Kim DD, Yeum JH, Cheong IW: Preparation and characterization of MRI-active gadolinium nano composite particles for neutron capture therapy. J Mater Chem 2011, 21: 15486. 10.1039/c1jm11608h
Arhen M, Selegard L, Klasson A, Soderlind F, Abrikossova N, Skoglund C, Bengtsson T, Engstrom M, Kall PO, Uvdal K: Synthesis and characterization of PEGylated Gd2O3 nanoparticles for MRI contrast enhancement. Langmuir 2010, 26: 5753. 10.1021/la903566y
Jung S, Kong J, Song S, Lee K, Lee T, Hwang H, Jeon S: Resistive switching characteristics of solution-processes TiO x for next-generation non-volatile memory application: transparency, flexibility and nano-scale memory feasibility. Microelectron Eng 2011, 88: 1143. 10.1016/j.mee.2011.03.054
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 2012, 51: 04DD06. 10.7567/JJAP.51.04DD06
Prakash A, Maikap S, Rahaman S, Majumdar S, Manna S, Ray SK: Resistive switching memory characteristics of Ge/GeO x nanowires and evidence of oxygen ion migration. Nano Res Lett 2013, 8: 220. 10.1186/1556-276X-8-220
Prakash A, Maikap S, Banerjee W, Jana D, Lai CS: Impact of electrically formed interfacial layer and improved memory characteristics of IrO x /high- κ x /W structures containing AlO x , GdO x . HfOx and TaOx switching materials. Nano Res Lett 2013, 8: 379.
Acknowledgements
This work was supported by the National Science Council (NSC) of Taiwan, under the contract no. NSC-102-2221-E-182-057-MY2.
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DJ carried out this research work, and AP helped fabricate the memory devices under the instruction of SM. YYC did TEM under the instruction of SM and JRY. HCC supported in the deposition of the Gd2O3 film. All the authors contributed to the revision of the manuscript, and they approved it for publication.
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Jana, D., Maikap, S., Prakash, A. et al. Enhanced resistive switching phenomena using low-positive-voltage format and self-compliance IrO x /GdO x /W cross-point memories. Nanoscale Res Lett 9, 12 (2014). https://doi.org/10.1186/1556-276X-9-12
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DOI: https://doi.org/10.1186/1556-276X-9-12