Methods for enhanced state retention within a resistive change cell
View Patent ↗A method for improving the stability of a resistive change cell is disclosed. The stability of a resistive change memory cell—that is, the tendency of the resistive change memory cell to retain its programmed resistive state—may, in certain applications, be compromised if the cell is programmed into an unstable or metastable state. In such applications, a programming method using bursts of sub-pulses within a pulse train is used to drive the resistive change cell material into a stable state during the programming operation, reducing resistance drift over time within the cell.
1. A method of adjusting a resistance of a nanotube fabric layer formed from carbon nanotubes, said method comprising:
applying a periodic electrical stimulus to said nanotube fabric layer for a fixed time;
wherein said periodic electrical stimulus has a frequency and a duty cycle, and wherein said fixed time is selected such that said periodic electrical stimulus successively stimulates said nanotube fabric layer multiple times; and
wherein said successive stimulation renders said nanotube fabric layer into a stable resistive state.
2. The method of claim 1 wherein said successive stimulation prevents said nanotube fabric layer from entering into a metastable state.
3. The method of claim 1 where said periodic electrical stimulus is a pulse train.
4. The method of claim 1 wherein said duty cycle is on the order of 20 percent.
5. The method of claim 1 wherein said duty cycle is on the order of 50 percent.
6. The method of claim 1 wherein said duty cycle is on the order of 80 percent.
7. The method of claim 1 wherein said frequency is on the order of 10 MHz.
8. The method of claim 1 wherein said nanotube fabric layer is adjusted from a high resistive state to a low resistive state.
9. The method of claim 1 wherein said nanotube fabric layer is adjusted from a low resistive state to a high resistive state.
10. The method of claim 1 wherein said nanotube fabric layer is adjusted from one predefined resistive range to one of at least two other predefined resistance ranges.
11. The method of claim 1 wherein said nanotube fabric layer is part of a resistive change memory cell.
12. The method of claim 1 wherein said nanotube fabric layer is part of a resistive change logic device.
13. The method of claim 1 wherein said nanotube fabric layer is part of a sensor element.
14. The method of claim 1 wherein said periodic electrical stimulus is a square wave.