Bipolar switching PCMO capacitor

1. A Pr x Ca 1-x MnO 3 (PCMO) thin film capacitor with bipolar switching characteristics, the capacitor comprising:

a bottom electrode;

a multi-layer PCMO film, with bipolar switching properties, overlying the bottom electrode including:

a nanocrystalline PCMO layer;

a polycrystalline PCMO layer; and,

a top electrode overlying the bi-layer PCMO film.

2. The capacitor of claim 1 wherein the nanocrystalline PCMO layer has crystal grains with a size in the range of 3 to 40 nanometers (nm).

3. The capacitor of claim 1 wherein the polycrystalline PCMO layer has crystal grains with a size in the range of 40 nm to epitaxial.

4. The capacitor of claim 1 wherein the bottom electrode is formed from a material selected from the group including Pt, Au, Ir, and a stack of materials including Pt/x/SiO2/Si and Ir/x/SiO2/Si, where x is a material selected from the group including Ti, TiN, and TaN.

5. The capacitor of claim 1 wherein the multi-layer PCMO film has the following bipolar switching properties:

a high resistance in the range of 10 to 1000 kilo ohms in response to a pulse having a voltage in the range of ±(2 to 10) volts (V), with a duration in the range of 5 nanosecond (ns) to 50 microseconds; and,

a low resistance in the range of 500 ohms to 10 kilo ohms, in response to a pulse having a voltage in the range of ±(2 to 10) V, with a duration in the range of 5 ns to 50 microseconds.

6. The capacitor of claim 1 wherein the nanocrystalline PCMO layer has a thickness in the range of 5 to 100 nanometers (nm); and,

wherein the polycrystalline PCMO layer has a thickness in the range of 5 to 100 nm.

7. The capacitor of claim 1 wherein the nanocrystalline PCMO layer has a first thickness;

wherein the polycrystalline PCMO layer has a second thickness; and,

wherein the multi-layer PCMO film has an overall greater resistance, a resistance ratio between the high and low resistance states that increases, and a switching voltage pulse amplitude that increases, in response to increasing the first and second thicknesses.

8. The capacitor of claim 1 wherein the multi-layer PCMO film has a first number of nanocrystalline and polycrystalline bi-layers.

9. The capacitor of claim 8 wherein the multi-layer PCMO film first number of bi-layers is in the range between 2 and 20.

10. The capacitor of claim 9 wherein each nanocrystalline PCMO layer has a first thickness;

wherein each polycrystalline PCMO layer has a second thickness;

wherein the multi-layer PCMO film has an overall lower resistance, a resistance ratio between the high and low resistance states that decreases, and a switching voltage pulse amplitude that increases, in response to increasing the first and second thicknesses, while decreasing the first number of bi-layers, and maintaining a constant overall thickness that is a thickness combination of each of the nanocrystalline and polycrystalline layers.

11. The capacitor of claim 1 wherein the nanocrystalline PCMO layer overlies the bottom electrode;

wherein the polycrystalline PCMO layer overlies the nanocrystalline layer; and,

wherein the multi-layer PCMO film has the following bipolar switching properties:

a high resistance in the range of 10 to 1000 kilo ohms in response to a pulse having a voltage in the range of −(2 to 10) V, with a duration in the range of 5 ns to 50 microseconds; and,

a low resistance in the range of 500 ohms to 10 kilo ohms, in response to a pulse having a voltage in the range of +(2 to 10) V, with a duration in the range of 5 ns to 50 microseconds.

12. The capacitor of claim 1 wherein the polycrystalline PCMO layer overlies the bottom electrode;

wherein the nanocrystalline PCMO layer overlies the polycrystalline layer; and,

wherein the multi-layer PCMO film has the following bipolar switching properties:

a high resistance in the range of 10 to 1000 kilo ohms in response to a pulse having a voltage in the range of +(2 to 10) V, with a duration in the range of 5 ns to 50 microseconds; and,

a low resistance in the range of 500 ohms to 10 kilo ohms, in response to a pulse having a voltage in the range of −(2 to 10) V, with a duration in the range of 5 ns to 50 microseconds.

13. The capacitor of claim 1 wherein the multi-layer PCMO film includes a polycrystalline content that is at least 20% of the total PCMO material.

14. A Pr x Ca 1-x MnO 3 (PCMO) thin film capacitor with selectable bipolar switching characteristics, the capacitor comprising:

a bottom electrode;

a multi-layer PCMO film, including a nanocrystalline PCMO layer and a polycrystalline PCMO layer, with selectable resistance switching properties responsive to the order of the PCMO layers; and,

a top electrode overlying the multi-layer PCMO film.

15. The capacitor of claim 14 wherein the multi-layer PCMO film order includes the polycrystalline PCMO layer overlying the nanocrystalline PCMO layer, and the resistance switching polarities as follows:

a high resistance responsive to a negative polarity voltage pulse; and,

a low resistance responsive to a positive polarity voltage pulse.

16. The capacitor of claim 14 wherein the multi-layer PCMO film order includes the nanocrystalline PCMO layer overlying the polycrystalline PCMO layer, and the resistance switching polarities as follows:

a high resistance responsive to a positive polarity voltage pulse; and,

a low resistance responsive to a negative polarity voltage pulse.