Improved Switching Uniformity and Low-Voltage Operation in ${\rm TaO}_{x}$-Based RRAM Using Ge Reactive Layer

Zhuo, Victor Yi-Qian; Jiang, Yu; Zhao, Rong; Shi, Lu; Yang, Yi; Chong, Tow Chong; Robertson, John

doi:10.1109/led.2013.2271545

Cited by 37 publications

(26 citation statements)

References 15 publications

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“…However, the 10G20T devices did show significant improvement in uniformity as can be seen in the substantial reduction of 53 % in the standard deviation (u) of VFORM when compared to the 20T devices. This coincides with results of our previous work whereby adding a Ge reactive layer was able to increase the spatial uniformities of the VSET and VRESET by 76 % and 28%, respectively[5]. Hence, low voltage operation and high uniformity were achieved in the lOG20T devices.Both the 20T and lOG20T devices show bipolar switching behavior with a positive VSET and a negative V RESET as shown in Fig.…”

supporting

confidence: 91%

“…Hence, it might be possible that at the Ge/TaOx interface, these trap centers trap carriers and facilitate the reformation of the conductive filament at elevated temperatures, leading to HRS retention failure. On the other hand, an advantage of this lower Ea for HRS retention is that it is easier for the 1 OG20T device to set, which is evident in the significantly lower VSET in the 1OG20T devices as compared to the 20T devices [5]. However, the tradeoff is that the HRS retention is affected to a slight extent as can be seen in Fig.…”

Section: Introductionmentioning

confidence: 96%

“…RON and ROFF switching parameters were achieved in TaOx-based RRAM, simply with the addition of a Ge reactive layer. The Ge/TaOx devices also showed large reductions in the operation voltages [5].…”

Section: Introductionmentioning

confidence: 97%

See 2 more Smart Citations

Thermal stability investigation in highly- uniform and low-voltage tantalum oxide-based RRAM

Zhuo

Jiang

Robertson

2014

2014 14th Annual Non-Volatile Memory Technology Symposium (NVMTS)

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Resistive switching behavior of TaO,-based resistive switching devices is investigated at temperatures of 25 ·C to 300 .c. Both the set and reset voltages decrease with increasing temperature. Long retention (>10 years at 150 .C) and good thermal stability were achieved for the TaO,-based RRAM. At elevated temperatures from 240 ·C to 300 ·C, the low resistance state exhibits no significant change with time. In contrast, the high resistance state (HRS) shows degradation followed by sudden failure. The HRS failure times for both TaO, and Ge/TaO, devices exhibit Arrhenius dependence with activation energies of 1.45 eV and 1.27 eV, respectively.

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supporting

confidence: 91%

Section: Introductionmentioning

confidence: 96%

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Thermal stability investigation in highly- uniform and low-voltage tantalum oxide-based RRAM

Zhuo

Jiang

Robertson

2014

2014 14th Annual Non-Volatile Memory Technology Symposium (NVMTS)

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“…Nevertheless, it is useful for the O vacancy to be in the positive charge state, to ensure controlled drift under the switching field. Experimentally, scavenger metal layer has been used to optimize the performance of RS memory cells [59,60]. Guo et al [56] rationalized that scavenger metal of larger work function than the parent metal electrode lowers the Fermi energy to ensure Ov in its positively charged state.…”

Section: Ov Formation Energies In Ta2o5 and Tio2mentioning

confidence: 99%

Identifying and Engineering the Electronic Properties of the Resistive Switching Interface

Hong

Zhang

Shi

2015

Journal of Elec Materi

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We study the electronic structures of TiO2/Ti4O7 and Ta2O5/TaO2 interfaces using the screened exchange (sX-LDA) functional. Both of these bilayer structures are useful infrastructures for high performance RRAMs. We find that the system Fermi energies of both interfaces are just above the conduction band edge of the corresponding stoichiometric oxides. According to the charge transition levels of the oxygen vacancies, the oxygen vacancies are stabilized at the -2 charged state in both Ta2O5 and TiO2. We propose to introduce interfacial dopants to shift the system Fermi energies downward so that the +2 charged oxygen vacancy can be stable, which is important for the controlled resistive switching under the electrical field. Several dipole models are presented to account for the ability of Fermi level shift due to the interfacial dopants. IntroductionMetal oxides have been widely used in the emerging nonvolatile memory technologies like the resistive random access memory (RRAM) [1,2] and the memristor [3][4][5]. Both of these devices are characterized by the reversible resistance switching (RS) which is commonly due to the growth and rupture of the conducting filaments (CFs) consisting of charged oxygen vacancies (Ov) [6][7][8]. Numerous reports have been published on metal oxides operating through this RS mechanism like TiO2 [9,10], Ta2O5 [11], SrTiO3 [12], NiO [13,14], and so on. Among various oxide candidates, TiO2 demonstrates both unipolar [9,10] and bipolar [15,16] RS. Transmission electron microscopy of the unipolar RS TiO2 has suggested that the CFs in unipolar switching are composed of Magneli phase Ti4O7 [10]. Recently, real time identification of the evolution of Ti4O7 CFs in TiO2 has been reported [17]. However, the problem of TiO2 is the co-existence of more than one stable substoichiometric Magneli phases which is unfavorable for long device endurance [18]. On the other hand, Ta2O5 keeps the longest endurance record among these oxides [11] and it operates in a bipolar manner. The long endurance of Ta2O5 based devices is partly attributed to only one stable substoichiometric phase, Ta, under 1000°C [18] despite of large amount of metastable substoichiometric phases such as TaO2. The in situ observation of CFs in Ta2O5 has recently been reported [19].One of the biggest challenges of these oxide based devices is the requirement for the electroforming process [20,21]. This could induce physical damages to the device due to oxygen gas release [22]. Besides, wide variance of device properties depends on the details of the electroforming which are yet to be understood. Therefore, it is essential to achieve electroforming free RS so as to eliminate the device variance for applicable computer circuits [20,21].

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“…According with the CF model, one of the factors to improve the uniformity of V-Set and V-Reset distributions is the stabilization of oxygen migrations. 19 Thus, it is possible that by irradiating the Pt/ZnO/Pt capacitor with UV illumination, the oxygen photodesorption may help stabilize the oxygen migration and could also confine the CFs, thus minimizing the dispersion of switching voltages.…”

Section: Effect Of Ultraviolet Illumination On Metal Oxide Resistive mentioning

confidence: 99%

Effect of ultraviolet illumination on metal oxide resistive memory

Retamal

Kang

et al. 2014

Applied Physics Letters

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Improved Switching Uniformity and Low-Voltage Operation in ${\rm TaO}_{x}$-Based RRAM Using Ge Reactive Layer

Cited by 37 publications

References 15 publications

Thermal stability investigation in highly- uniform and low-voltage tantalum oxide-based RRAM

Thermal stability investigation in highly- uniform and low-voltage tantalum oxide-based RRAM

Identifying and Engineering the Electronic Properties of the Resistive Switching Interface

Effect of ultraviolet illumination on metal oxide resistive memory

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