Abstract:The development of a resistance switching (RS) memory cell that contains rectifi cation functionality in itself, highly reproducible RS performance, and electroforming-free characteristics is an impending task for the development of resistance switching random access memory. In this work, a two-layered dielectric structure consisting of HfO 2 and Ta 2 O 5 layers, which are in contact with the TiN and Pt electrode, is presented for achieving these tasks simultaneously in one sample confi guration. The HfO 2 lay… Show more
“…To mitigate such problems, Yoon et al recently adopted the Pt/ Ta 2 O 5 /HfO 2 /TiN structure, wherein the HfO 2 /TiN interface comprises the quasi-Ohmic contact and the Pt/Ta 2 O 5 contact has a high Schottky barrier that suppresses the carrier transport during the set and reset switching. 19 This is consistent with the case shown in Fig. 1(b).…”
Electronic bipolar resistance switching (eBRS) in an Al/TiOx/Al structure, where the TiOx layer was reactively sputter-deposited, was examined in conjunction with a structural analysis using transmission electron microscopy. A thin (3-5 nm) insulating Al(Ti)Ox layer was formed at the bottom Al electrode interface, which provided the necessary asymmetric potential barrier for the eBRS to emerge, whereas the top Al electrode interface appeared to have provided the fluent carrier (electron) injection. The set and reset switching were related to the trapping and detrapping of the carriers at the trap centers, the characteristic energy of which was ∼0.86 eV, across the entire electrode area. The general features of this material system as the feasible RS memory were insufficient: endurance cycle, <∼8000, and retention time at 85 °C, 10(6) s. However, the detailed analysis of the switching behavior based on the space-charge limited current conduction mechanism, and its variation with the switching cycles, provided useful information on the general features of the eBRS, which could also be applicable to other binary (or even ternary) metal-oxide RS systems based on the electronic switching mechanism.
“…To mitigate such problems, Yoon et al recently adopted the Pt/ Ta 2 O 5 /HfO 2 /TiN structure, wherein the HfO 2 /TiN interface comprises the quasi-Ohmic contact and the Pt/Ta 2 O 5 contact has a high Schottky barrier that suppresses the carrier transport during the set and reset switching. 19 This is consistent with the case shown in Fig. 1(b).…”
Electronic bipolar resistance switching (eBRS) in an Al/TiOx/Al structure, where the TiOx layer was reactively sputter-deposited, was examined in conjunction with a structural analysis using transmission electron microscopy. A thin (3-5 nm) insulating Al(Ti)Ox layer was formed at the bottom Al electrode interface, which provided the necessary asymmetric potential barrier for the eBRS to emerge, whereas the top Al electrode interface appeared to have provided the fluent carrier (electron) injection. The set and reset switching were related to the trapping and detrapping of the carriers at the trap centers, the characteristic energy of which was ∼0.86 eV, across the entire electrode area. The general features of this material system as the feasible RS memory were insufficient: endurance cycle, <∼8000, and retention time at 85 °C, 10(6) s. However, the detailed analysis of the switching behavior based on the space-charge limited current conduction mechanism, and its variation with the switching cycles, provided useful information on the general features of the eBRS, which could also be applicable to other binary (or even ternary) metal-oxide RS systems based on the electronic switching mechanism.
“…Additionally, it is worth noting from the XPS results in Fig. 2c that the binding energy of Ta 4f well coincided with the reported value of the Ta 4f peak (26.6 eV for Ta 4f7/2 and 28.4 eV for Ta 4f5/2) in Ta 2 O 5 [3, 8]. For HfO 2- x , grown by directly oxidizing the metal Hf via oxygen plasma with a duration 1600 s, the core-level Hf4f7/2–Hf4f5/2 was observed at an energy corresponding to the non-stoichiometric HfO 2 (12.7–18.5 eV) [9], which indicated the presence of the neutral oxygen vacancy in our HfO 2- x layer.…”
Section: Resultssupporting
confidence: 77%
“…1b). The wealth of self-rectifying phenomena in different structures reported so far, while either too high switching voltage [3, 4] or insufficient ON/OFF window [5, 6] is exposed by most reports.Fig. 1
a The sneak-path issue happened in crossbar structure and b typical I–V characteristics and read scheme of 1R with S-R cells
…”
In this study, we present a bilayer resistive switching memory device with Pt/Ta2O5/HfO2-x/Hf structure, which shows sub-1 μA ultralow operating current, median switching voltage, adequate ON/OFF ratio, and simultaneously containing excellent self-rectifying characteristics. The control sample with single HfO2-x structure shows bidirectional memory switching properties with symmetrical I–V curve in low resistance state. After introducing a 28-nm-thick Ta2O5 layer on HfO2-x layer, self-rectifying phenomena appeared, with a maximum self-rectifying ratio (RR) of ~4 × 103 observed at ±0.5 V. Apart from being a series resistance for the cell, the Ta2O5 rectifying layer also served as an oxygen reservoir which remains intact during the whole switching cycle.
“…[ 16,24,25 ] In addition, the integration potential of the crossbar array confi guration could also be restricted by the electroforming process. [ 26 ] On the other hand, increasing demand for high density data storage with continuous downscaling has triggered research attention towards multilevel RRAM which offers an opportunity to store more than 2-bits in a single cell. [ 27,28 ] Therefore, a large ON/OFF ratio of different resistive states is generally required to keep the stable operation of multilevel switching, [ 29,30 ] and it is also an important feature for the resistive memory to avoid misreading during the device operation.…”
(CFs) formation/rupture within the insulating layer leads to the resistive switching in RRAM, which can offer the possibility to scale down the memory device to less than 10 nm. [ 2,15,16,23 ] In order to activate the fresh resistive memory into switching states, the electroforming process, which usually adopts a higher voltage than the usual operation voltage, is needed to form the localized semipermanent conductive fi lament inside the active materials. [ 8,16,23 ] However, the device yield and the switching performance would be limited with high electroforming voltage which may cause permanent damage to the RRAM. [ 16,24,25 ] In addition, the integration potential of the crossbar array confi guration could also be restricted by the electroforming process. [ 26 ] On the other hand, increasing demand for high density data storage with continuous downscaling has triggered research attention towards multilevel RRAM which offers an opportunity to store more than 2-bits in a single cell. [ 27,28 ] Therefore, a large ON/OFF ratio of different resistive states is generally required to keep the stable operation of multilevel switching, [ 29,30 ] and it is also an important feature for the resistive memory to avoid misreading during the device operation.Several propositions have been developed to reduce the electroforming voltage with the improvement of the switching performances. [ 7,8,11,31,32 ] However, these methods commonly involve relatively complex fabrication process [ 8,11 ] or require high temperature for thermal annealing treatment [ 7,32 ] which may degrade the previously deposited selector or diode performance and are not suitable for stackable integration. [ 9,33 ] Furthermore, the high temperature processes are also not suitable to fabricate memory devices on the thermal instability fl exible substrates. [ 34,35 ] On the other hand, to increase the ON/OFF ratio of resistive switching memory, some methods have been developed. [ 25,29,36,37 ] For example, the ON/OFF ratio can be increased by doping boron (B) atoms into carbon nanotubes [ 29 ] or manganese (Mn) atoms into ZnO thin fi lm, [ 37 ] of which the fabrication processes are complicated and not easy to control.In order to meet the desirable requirements of (a) lowering the electroforming voltage ( V forming ) and (b) enhancing the ON/ OFF ratio, a simple approach was proposed. In this report, the Amorphous Si (a-Si) based memory devices that offer signifi cant improvement in switching performance are fabricated by inserting a gold nanoparticles (Au NPs) monolayer between the amorphous Si and inert bottom electrodes. It is demonstrated that the Au NPs-interlayer amorphous Si memory devices deliver great improvements in lowering the electroforming voltage as well as enhancing the ON/OFF ratio, as compared to a pure amorphous Si memory structure. The switching mechanism is due to the modifi ed electric fi eld distribution with the insertion of Au NPs, which can directly affect the dynamic transport of ions and lead to the change of fi lament growth. T...
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