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Dynamic-load-enabled ultra-low power multiple-state RRAM devices.

Yang X, Chen IW - Sci Rep (2012)

Bottom Line: Bipolar resistance-switching materials allowing intermediate states of wide-varying resistance values hold the potential of drastically reduced power for non-volatile memory.This approach is entirely scalable and applicable to other bipolar RRAM with intermediate states.The projected power is 12 nW for a 100 × 100 nm(2) device and 500 pW for a 10 × 10 nm(2) device.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104-6272, USA.

ABSTRACT
Bipolar resistance-switching materials allowing intermediate states of wide-varying resistance values hold the potential of drastically reduced power for non-volatile memory. To exploit this potential, we have introduced into a nanometallic resistance-random-access-memory (RRAM) device an asymmetric dynamic load, which can reliably lower switching power by orders of magnitude. The dynamic load is highly resistive during on-switching allowing access to the highly resistive intermediate states; during off-switching the load vanishes to enable switching at low voltage. This approach is entirely scalable and applicable to other bipolar RRAM with intermediate states. The projected power is 12 nW for a 100 × 100 nm(2) device and 500 pW for a 10 × 10 nm(2) device. The dynamic range of the load can be increased to allow power to be further decreased by taking advantage of the exponential decay of wave-function in a newly discovered nanometallic random material, reaching possibly 1 pW for a 10×10 nm(2) nanometallic RRAM device.

No MeSH data available.


Related in: MedlinePlus

(a) I–V curves for RRAM device with and without asymmetric load, which reduces current and off-switching voltage.Inset: corresponding R–V curves. Cell size: 100×100 μm2. Off-switching (b) power Poff and (c) voltage Voff* and on-resistance Ronvs.Rex for three cells of different sizes, showing systematic size-dependent Poff and Voff decreases and Ron increases. Inset of (b): Roff/RonvsRex for cells of different sizes. (d) Scaling behavior of Ron and Voff*. See Figure 1 for scaling behavior of Poff.
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f4: (a) I–V curves for RRAM device with and without asymmetric load, which reduces current and off-switching voltage.Inset: corresponding R–V curves. Cell size: 100×100 μm2. Off-switching (b) power Poff and (c) voltage Voff* and on-resistance Ronvs.Rex for three cells of different sizes, showing systematic size-dependent Poff and Voff decreases and Ron increases. Inset of (b): Roff/RonvsRex for cells of different sizes. (d) Scaling behavior of Ron and Voff*. See Figure 1 for scaling behavior of Poff.

Mentions: We next demonstrate that the plateau resistance can be increased and the off-switching power drastically reduced by introducing a dynamic load that has an asymmetric response to voltage. This was achieved using a diode in parallel with another external load Rex, as schematically shown in Figure 2c. Under a positive bias which includes off-switching, the diode is in the forward direction (Rd~0) allowing Rex to be short-circuited. So the net load is nearly Rl, still equal to 300 Ω. Under a negative bias which includes on-switching, the diode is in the reverse direction and is almost open-circuited. Thus the net load is the sum of 300 Ω and Rex. In reality, under a positive bias, a typical diode also introduces a positive voltage drift due to its threshold voltage Vth. (Vth can be as low as 0.2 V in a Schottky diode, but is 0.6 V in the silicon diode used in the experiment described here.) In addition, the diode in the reverse direction has a characteristic resistance Rd which is 100 MΩ in our experiment. As shown in Figure 4a for a 100×100 μm2 device, such a diode results in a switching curve with ~10× reduction in the on-switching current and ~10× increase in plateau resistance (Figure 4a inset). Under a positive bias, current increase starts near Vth~0.6 V and off-switching occurs at V*~1.4 V, corresponding to a maximum in current and a minimum in resistance (being Rc+300 Ω). For this (on) resistance and V*, the off-switching P is 0.25 mW.


Dynamic-load-enabled ultra-low power multiple-state RRAM devices.

Yang X, Chen IW - Sci Rep (2012)

(a) I–V curves for RRAM device with and without asymmetric load, which reduces current and off-switching voltage.Inset: corresponding R–V curves. Cell size: 100×100 μm2. Off-switching (b) power Poff and (c) voltage Voff* and on-resistance Ronvs.Rex for three cells of different sizes, showing systematic size-dependent Poff and Voff decreases and Ron increases. Inset of (b): Roff/RonvsRex for cells of different sizes. (d) Scaling behavior of Ron and Voff*. See Figure 1 for scaling behavior of Poff.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3473363&req=5

f4: (a) I–V curves for RRAM device with and without asymmetric load, which reduces current and off-switching voltage.Inset: corresponding R–V curves. Cell size: 100×100 μm2. Off-switching (b) power Poff and (c) voltage Voff* and on-resistance Ronvs.Rex for three cells of different sizes, showing systematic size-dependent Poff and Voff decreases and Ron increases. Inset of (b): Roff/RonvsRex for cells of different sizes. (d) Scaling behavior of Ron and Voff*. See Figure 1 for scaling behavior of Poff.
Mentions: We next demonstrate that the plateau resistance can be increased and the off-switching power drastically reduced by introducing a dynamic load that has an asymmetric response to voltage. This was achieved using a diode in parallel with another external load Rex, as schematically shown in Figure 2c. Under a positive bias which includes off-switching, the diode is in the forward direction (Rd~0) allowing Rex to be short-circuited. So the net load is nearly Rl, still equal to 300 Ω. Under a negative bias which includes on-switching, the diode is in the reverse direction and is almost open-circuited. Thus the net load is the sum of 300 Ω and Rex. In reality, under a positive bias, a typical diode also introduces a positive voltage drift due to its threshold voltage Vth. (Vth can be as low as 0.2 V in a Schottky diode, but is 0.6 V in the silicon diode used in the experiment described here.) In addition, the diode in the reverse direction has a characteristic resistance Rd which is 100 MΩ in our experiment. As shown in Figure 4a for a 100×100 μm2 device, such a diode results in a switching curve with ~10× reduction in the on-switching current and ~10× increase in plateau resistance (Figure 4a inset). Under a positive bias, current increase starts near Vth~0.6 V and off-switching occurs at V*~1.4 V, corresponding to a maximum in current and a minimum in resistance (being Rc+300 Ω). For this (on) resistance and V*, the off-switching P is 0.25 mW.

Bottom Line: Bipolar resistance-switching materials allowing intermediate states of wide-varying resistance values hold the potential of drastically reduced power for non-volatile memory.This approach is entirely scalable and applicable to other bipolar RRAM with intermediate states.The projected power is 12 nW for a 100 × 100 nm(2) device and 500 pW for a 10 × 10 nm(2) device.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104-6272, USA.

ABSTRACT
Bipolar resistance-switching materials allowing intermediate states of wide-varying resistance values hold the potential of drastically reduced power for non-volatile memory. To exploit this potential, we have introduced into a nanometallic resistance-random-access-memory (RRAM) device an asymmetric dynamic load, which can reliably lower switching power by orders of magnitude. The dynamic load is highly resistive during on-switching allowing access to the highly resistive intermediate states; during off-switching the load vanishes to enable switching at low voltage. This approach is entirely scalable and applicable to other bipolar RRAM with intermediate states. The projected power is 12 nW for a 100 × 100 nm(2) device and 500 pW for a 10 × 10 nm(2) device. The dynamic range of the load can be increased to allow power to be further decreased by taking advantage of the exponential decay of wave-function in a newly discovered nanometallic random material, reaching possibly 1 pW for a 10×10 nm(2) nanometallic RRAM device.

No MeSH data available.


Related in: MedlinePlus