Multilayer ferroelectric data storage system with regenerative read

1. A system comprising:

a first storage layer having a first coercive potential and a first polarization;

a second storage layer having a second coercive potential that is less than the first coercive potential and a second polarization that is coupled to the first polarization;

a writer for performing a write operation in which a write potential is imposed across the first and second storage layers, such that the first coercive potential is exceeded across the first storage layer and the second coercive potential is exceeded across the second storage layer; and

a reader for performing a read operation in which a read potential is imposed across the first and second storage layers, such that the second coercive potential is exceeded across the second storage layer and the first coercive potential is not exceeded across the first storage layer.

2. The system of claim 1 , wherein the second storage layer is ferroelectrically coupled to the first storage layer.

3. The system of claim 1 , wherein the second storage layer is antiferroelectrically coupled to the first storage layer.

4. The system of claim 1 , wherein the reader further senses the second polarization as a function of a switching signal based on a compensation charge flow that is induced when the second polarization is aligned according to the read potential, independently of the first polarization.

5. The system of claim 1 , further comprising a substrate formed under the conducting layer.

6. The system of claim 5 , further comprising a dielectric spacer formed between the first storage layer and the second storage layer.

7. The system of claim 1 , wherein each of the reader and the writer is a two-terminal device comprising a bottom electrode and a top electrode.

8. The system of claim 7 , further comprising a translating probe electrode for selecting a bit region within the first and second storage layers.

9. The system of claim 7 , further comprising an addressable electrode layer for selecting a memory cell within the first and second storage layers.

10. The system of claim 1 , further comprising:

a third storage layer having a third coercive potential that is greater than the second coercive potential and different from the first coercive potential; and

a fourth storage layer having a fourth coercive potential that is less than the third coercive potential and different from the second coercive potential;

wherein the third storage layer has a third polarization and the fourth storage layer has a fourth polarization that is coupled to the third polarization, independently of the first and second polarizations.

11. A method of reading and writing data, the method comprising:

writing data to first and second ferroelectric layers by imposing a write voltage across the first and second ferroelectric layers such that a first coercive voltage is exceeded across the first ferroelectric layer and a second coercive voltage is exceeded across the second ferroelectric layer; and

reading data from the second ferroelectric layer by imposing a read voltage across the first and second ferroelectric layers such that the second coercive voltage is exceeded across the second ferroelectric layer while the first coercive voltage is not exceeded across the first ferroelectric layer.

12. The method of claim 11 , wherein reading data from the second ferroelectric layer comprises sensing a signal based on a compensation charge flow that is induced by polarization switching in the second ferroelectric layer.

13. The method of claim 11 , further comprising positioning a translating read/write probe over the first and second ferroelectric layers.

14. The method of claim 11 , further comprising addressing a memory cell region of the first and second ferroelectric layers.

15. The method of claim 11 , further comprising writing data to third and fourth ferroelectric layers by imposing a second write voltage across the first, second, third and fourth ferroelectric layers such that a third coercive voltage is exceeded across the third ferroelectric layer and a fourth coercive voltage is exceeded across the fourth ferroelectric layer, while the first coercive voltage is not exceeded across the first ferroelectric layer.

16. The method of claim 15 , further comprising reading data from the fourth ferroelectric layer by imposing a second read voltage across the first, second, third and fourth ferroelectric layers such that the fourth coercive voltage is exceeded across the fourth ferroelectric layer, while the first coercive voltage is not exceeded across the first ferroelectric layer, the second coercive voltage is not exceeded across the second ferroelectric layer and the third coercive voltage is not exceeded across the third ferroelectric layer.

17. A system comprising:

a hard ferroelectric layer having a hard layer polarization and a hard layer coercive potential;

a soft ferroelectric layer having a soft layer polarization coupled to the hard layer polarization and a soft layer coercive potential that is less than the hard layer coercive potential;

a writer for imposing a write potential across the hard and soft ferroelectric layers such that the hard layer polarization and the soft layer polarization are aligned according to the write potential; and

a reader for imposing a read potential across the hard and soft ferroelectric layers such that the soft layer polarization is aligned according to the read potential while the hard layer polarization retains an existing orientation, and for sensing a readback signal based on switching of the soft layer polarization.

18. The system of claim 17 , wherein the hard and soft ferroelectric layers are ferroelectrically coupled.

19. The system of claim 17 , wherein the hard and soft ferroelectric layers are antiferroelectrically coupled.

20. The system of claim 17 , further comprising means for translating the reader and the writer above the hard and soft ferroelectric layers in order to select a bit region for the reader and the writer.

21. The system of claim 17 , further comprising means for addressing the hard and soft ferroelectric layers in order to select a memory cell for the reader and the writer.

22. The system of claim 17 , wherein the hard ferroelectric layer is a first hard ferroelectric layer having a first hard layer coercive potential, the soft ferroelectric layer is a first soft ferroelectric layer having a first soft layer coercive potential, and further comprising:

a second hard ferroelectric layer having a second hard layer polarization and a second hard layer coercive potential that is greater than the first soft layer coercive potential and less than the first hard layer coercive potential; and

a second soft ferroelectric layer having a second soft layer polarization coupled to the second hard layer polarization, independently of the first hard layer polarization, and having a second soft layer coercive potential that is less than the first soft layer coercive potential.

23. The system of claim 22 , wherein the write potential is a first write potential and the writer is further for imposing a second write potential across the first and second hard ferroelectric layers and the first and second soft ferroelectric layers, such that the second hard layer polarization and the second soft layer polarization are aligned according to the second write potential, independently of the first hard layer.

24. The system of claim 22 , wherein the read potential is a first read potential and the readback signal is a first readback signal, and wherein the reader is further for imposing a second read potential across the first and second hard ferroelectric layers and the first and second soft ferroelectric layers, such that the second soft layer polarization is aligned according to the second read potential while the second hard layer polarization retains an existing orientation, and wherein the reader further senses a second readback signal based on switching of the second soft layer polarization, independently of the first soft layer.