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Deterministic conversion between memory and threshold resistive switching via tuning the strong electron correlation.

Peng HY, Li YF, Lin WN, Wang YZ, Gao XY, Wu T - Sci Rep (2012)

Bottom Line: Intensive investigations have been launched worldwide on the resistive switching (RS) phenomena in transition metal oxides due to both fascinating science and potential applications in next generation nonvolatile resistive random access memory (RRAM) devices.It is noteworthy that most of these oxides are strongly correlated electron systems, and their electronic properties are critically affected by the electron-electron interactions.Moreover, from first-principles calculations and x-ray absorption spectroscopy studies, we found that the strong electron correlations and the exchange interactions between Ni and O orbitals play deterministic roles in the RS operations.

View Article: PubMed Central - PubMed

Affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore.

ABSTRACT
Intensive investigations have been launched worldwide on the resistive switching (RS) phenomena in transition metal oxides due to both fascinating science and potential applications in next generation nonvolatile resistive random access memory (RRAM) devices. It is noteworthy that most of these oxides are strongly correlated electron systems, and their electronic properties are critically affected by the electron-electron interactions. Here, using NiO as an example, we show that rationally adjusting the stoichiometry and the associated defect characteristics enables controlled room temperature conversions between two distinct RS modes, i.e., nonvolatile memory switching and volatile threshold switching, within a single device. Moreover, from first-principles calculations and x-ray absorption spectroscopy studies, we found that the strong electron correlations and the exchange interactions between Ni and O orbitals play deterministic roles in the RS operations.

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Conversions between memory and threshold switching modes.(a) Memory switching was observed in the Pt/NiO/ITO device when a compliance current (CC) of 1 mA was used. The blue and red lines represent ten set and reset cycles, respectively. (b) Threshold switching was achieved when CC was increased to 10 mA. Ten cycles of operation are shown. Inset: Polarity dependence of the forming process, and only the positive bias leads to the threshold switching. (c) Threshold switching was retained even after CC was reduced to 1 mA, while the hysteresis loop became smaller. (d) After annealing in vacuum at 300°C for 30 minutes, the threshold switching was converted back to the memory switching which resembles the data shown in (a). (e) Current-controlled memory switching. A compliance voltage of 2 V was used during the reset operation. (f) Current-controlled sweeping curve corresponding to the voltage-controlled threshold switching mode, exhibiting negative differential resistance.
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f2: Conversions between memory and threshold switching modes.(a) Memory switching was observed in the Pt/NiO/ITO device when a compliance current (CC) of 1 mA was used. The blue and red lines represent ten set and reset cycles, respectively. (b) Threshold switching was achieved when CC was increased to 10 mA. Ten cycles of operation are shown. Inset: Polarity dependence of the forming process, and only the positive bias leads to the threshold switching. (c) Threshold switching was retained even after CC was reduced to 1 mA, while the hysteresis loop became smaller. (d) After annealing in vacuum at 300°C for 30 minutes, the threshold switching was converted back to the memory switching which resembles the data shown in (a). (e) Current-controlled memory switching. A compliance voltage of 2 V was used during the reset operation. (f) Current-controlled sweeping curve corresponding to the voltage-controlled threshold switching mode, exhibiting negative differential resistance.

Mentions: Experimentally, NiO thin films with a thickness of 200 nm were grown using pulsed laser deposition (PLD), and they exhibit good crystalline quality (see Supplementary Fig. S1 online). We found that selecting the bottom electrode and adjusting the switching conditions are effective to tune the volatility of resistive switching, which, as we will show later, is linked with the modifications of stoichiometry in NiO. In polycrystalline NiO thin films prepared on tin-doped indium oxide (ITO) coated glass substrates, we observed the typical unipolar memory switching when a compliance current (CC) of 1 mA was used in the set operation (Fig. 2a). This memory switching in the NiO/ITO device is stable and reproducible with good endurance and retention (see Supplementary Fig. S2 online). The threshold switching was obtained when the CC was increased to 10 mA, which corresponds to a current density of 44.4 A/cm2 (Fig. 2b). Even after the CC returned back to 1 mA, the threshold switching persisted, as shown in Figure 2c. On the other hand, the reference NiO devices fabricated on a Pt layer (200 nm) coated Si wafer show only memory switching as the CC varies between 1 and 10 mA (see Supplementary Fig. S1 online). This contrast underscores the critical role of the bottom electrode.


Deterministic conversion between memory and threshold resistive switching via tuning the strong electron correlation.

Peng HY, Li YF, Lin WN, Wang YZ, Gao XY, Wu T - Sci Rep (2012)

Conversions between memory and threshold switching modes.(a) Memory switching was observed in the Pt/NiO/ITO device when a compliance current (CC) of 1 mA was used. The blue and red lines represent ten set and reset cycles, respectively. (b) Threshold switching was achieved when CC was increased to 10 mA. Ten cycles of operation are shown. Inset: Polarity dependence of the forming process, and only the positive bias leads to the threshold switching. (c) Threshold switching was retained even after CC was reduced to 1 mA, while the hysteresis loop became smaller. (d) After annealing in vacuum at 300°C for 30 minutes, the threshold switching was converted back to the memory switching which resembles the data shown in (a). (e) Current-controlled memory switching. A compliance voltage of 2 V was used during the reset operation. (f) Current-controlled sweeping curve corresponding to the voltage-controlled threshold switching mode, exhibiting negative differential resistance.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3369197&req=5

f2: Conversions between memory and threshold switching modes.(a) Memory switching was observed in the Pt/NiO/ITO device when a compliance current (CC) of 1 mA was used. The blue and red lines represent ten set and reset cycles, respectively. (b) Threshold switching was achieved when CC was increased to 10 mA. Ten cycles of operation are shown. Inset: Polarity dependence of the forming process, and only the positive bias leads to the threshold switching. (c) Threshold switching was retained even after CC was reduced to 1 mA, while the hysteresis loop became smaller. (d) After annealing in vacuum at 300°C for 30 minutes, the threshold switching was converted back to the memory switching which resembles the data shown in (a). (e) Current-controlled memory switching. A compliance voltage of 2 V was used during the reset operation. (f) Current-controlled sweeping curve corresponding to the voltage-controlled threshold switching mode, exhibiting negative differential resistance.
Mentions: Experimentally, NiO thin films with a thickness of 200 nm were grown using pulsed laser deposition (PLD), and they exhibit good crystalline quality (see Supplementary Fig. S1 online). We found that selecting the bottom electrode and adjusting the switching conditions are effective to tune the volatility of resistive switching, which, as we will show later, is linked with the modifications of stoichiometry in NiO. In polycrystalline NiO thin films prepared on tin-doped indium oxide (ITO) coated glass substrates, we observed the typical unipolar memory switching when a compliance current (CC) of 1 mA was used in the set operation (Fig. 2a). This memory switching in the NiO/ITO device is stable and reproducible with good endurance and retention (see Supplementary Fig. S2 online). The threshold switching was obtained when the CC was increased to 10 mA, which corresponds to a current density of 44.4 A/cm2 (Fig. 2b). Even after the CC returned back to 1 mA, the threshold switching persisted, as shown in Figure 2c. On the other hand, the reference NiO devices fabricated on a Pt layer (200 nm) coated Si wafer show only memory switching as the CC varies between 1 and 10 mA (see Supplementary Fig. S1 online). This contrast underscores the critical role of the bottom electrode.

Bottom Line: Intensive investigations have been launched worldwide on the resistive switching (RS) phenomena in transition metal oxides due to both fascinating science and potential applications in next generation nonvolatile resistive random access memory (RRAM) devices.It is noteworthy that most of these oxides are strongly correlated electron systems, and their electronic properties are critically affected by the electron-electron interactions.Moreover, from first-principles calculations and x-ray absorption spectroscopy studies, we found that the strong electron correlations and the exchange interactions between Ni and O orbitals play deterministic roles in the RS operations.

View Article: PubMed Central - PubMed

Affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore.

ABSTRACT
Intensive investigations have been launched worldwide on the resistive switching (RS) phenomena in transition metal oxides due to both fascinating science and potential applications in next generation nonvolatile resistive random access memory (RRAM) devices. It is noteworthy that most of these oxides are strongly correlated electron systems, and their electronic properties are critically affected by the electron-electron interactions. Here, using NiO as an example, we show that rationally adjusting the stoichiometry and the associated defect characteristics enables controlled room temperature conversions between two distinct RS modes, i.e., nonvolatile memory switching and volatile threshold switching, within a single device. Moreover, from first-principles calculations and x-ray absorption spectroscopy studies, we found that the strong electron correlations and the exchange interactions between Ni and O orbitals play deterministic roles in the RS operations.

Show MeSH
Related in: MedlinePlus