Passive electrically switchable circuit element having improved tunability and method for its manufacture
A resistive switching device and methods for making the same are disclosed. In the above said device, a resistive switching layer is interposed between opposing electrodes. The resistive switching layer comprises at least two sub-layers of switchable insulative material characterized by different ionic mobilities.
1. Apparatus comprising a resistive switching layer interposed between opposing electrodes, wherein the resistive switching layer comprises a plurality of alternating sub-layers of switchable insulative material, wherein at least two sub-layers of switchable insulative material are characterized by different ionic mobilities, and wherein a conductive filament or a plurality of conductive filaments are formed when voltage is applied between the opposing electrodes.
2. The apparatus of claim 1 , wherein the sub-layers alternate between a material of higher ionic mobility and a material of lower ionic mobility.
3. The apparatus of claim 1 , wherein sub-layers of a first material having a first ionic mobility are interposed by sub-layers of a second material having a second ionic mobility.
4. The apparatus of claim 3 , wherein the layers of the second material are spaced at intervals that depend on position in the normal direction within the switching layer.
5. The apparatus of claim 1 , wherein at least two said materials characterized by different ionic mobilities have different densities of grain boundaries.
6. The apparatus of claim 1 , wherein at least one said resistive switching layer is conformed to provide a switchable resistance in an electronic circuit.
7. The apparatus of claim 1 , wherein at least one said resistive switching layer is conformed to provide a switchable capacitance in an electronic circuit.
8. A method for making a resistive switching device, comprising depositing a lower electrode layer on a substrate, forming over the lower electrode layer in contiguous sequence a plurality of alternating sub-layers of switchable insulative material, wherein at least two sub-layers of switchable insulative material are characterized by different ionic mobilities, and depositing an upper electrode layer over the sub-layers of switchable insulative material, wherein a conductive filament or a plurality of conductive filaments forms when voltage is applied between the lower electrode layer and the upper electrode layer of the resistive switching device.
9. The method of claim 8 , wherein the forming step comprises forming, in alternation, sub-layers having a respective first and second ionic mobility.
10. The method of claim 8 , further comprising, during the forming step, regulating the thicknesses of the sub-layers such that the sub-layers of at least one said switchable insulative material are spaced at intervals that depend on distance from the substrate.
11. The method of claim 8 , wherein the forming step comprises annealing the sub-layers.
12. The method of claim 11 , wherein the annealing is carried out so as to induce a different density of grain boundaries in each of at least two said switchable insulative materials.
13. The method of claim 8 , further comprising completing the manufacture of an electronic circuit in which at least one said resistive switching device is conformed to provide switchable resistance.
14. The method of claim 8 , further comprising completing the manufacture of an electronic circuit in which at least one said resistive switching device is conformed to provide switchable capacitance.