Phase change material gradient structures and methods

1. A method of forming a memory cell, comprising:

forming a first electrode material coupled to a first conductive line;

forming a phase change material gradient on the first electrode material, wherein a phase change material comprises a chemical gradient with an active material that actively changes between an amorphous state and a crystalline state that is formed at least partially by a predetermined selection of a plurality of different chemicals to be deposited from separate sources;

forming a second electrode material on the phase change material gradient; and

forming a second conductive line coupled to the second electrode material.

2. The method of claim 1 , wherein forming the first electrode material includes forming the first electrode material on the first conductive line corresponding to the memory cell.

3. The method of claim 1 , wherein forming the phase change material gradient includes forming the active material of a phase change memory cell.

4. The method of claim 1 , wherein forming the phase change material gradient includes forming a number of chalcogenide alloys.

5. The method of claim 4 , wherein forming the number of chalcogenide alloys includes forming at least one of the number of chalcogenide alloys having a variation in stoichiometry.

6. The method of claim 5 , wherein forming the at least one of the number of chalcogenide alloys having the variation in stoichiometry includes forming a number of different and adjacent chalcogenide alloys.

7. The method of claim 5 , further comprising forming the at least one of the number of chalcogenide alloys by supplying a first element at a substantially constant rate and/or concentration and supplying a second element with a predetermined variation in a rate and/or a concentration.

8. The method of claim 7 , further comprising supplying a third element with a predetermined variation in a rate and/or a concentration.

9. The method of claim 5 , further comprising forming the at least one of the number of chalcogenide alloys by supplying a first element with a predetermined increase in a rate and/or a concentration and by supplying a second element with a predetermined decrease in the rate and/or the concentration.

10. A method of forming a memory cell, comprising:

forming an active storage element material and an active select device material arranged in series between a pair of electrodes; and

forming, at least partially by a predetermined selection of a plurality of different chemicals to be deposited from separate sources, a chemical gradient in a phase change material in at least one of the active storage element material and the active select device material.

11. The method of claim 10 , further comprising forming the active storage element material and the active select device material from a number of chalcogenide alloys.

12. The method of claim 10 , further comprising forming an electrode material between the active storage element material and the active select device material.

13. The method of claim 10 , wherein forming the active storage element material includes forming an active resistance variable storage element material.

14. The method of claim 10 , wherein forming the active select device material includes forming an ovonic threshold switch.

15. The method of claim 10 , including utilizing an ion implantation process to form the gradient.

16. The method of claim 15 , wherein utilizing the ion implantation process includes implanting a dopant.

17. The method of claim 10 , including utilizing a physical vapor deposition process to form the gradient.

18. The method of claim 10 , including utilizing an outdiffusion and/or outgassing process to form the gradient.

19. A memory cell structure, comprising:

a phase change material of a memory cell formed between a first electrode and a second electrode, wherein the phase change material comprises a phase change material gradient; and

a select device material of the memory cell formed between the second electrode and a third electrode.

20. The structure of claim 19 , wherein the first electrode is coupled to a conductive line corresponding to the memory cell.

21. The structure of claim 19 , wherein the third electrode is coupled to a conductive line corresponding to the memory cell.

22. The structure of claim 19 , wherein the phase change material gradient is formed from a number of different chalcogenide alloys.

23. The structure of claim 22 , wherein at least one of the number of different chalcogenide alloys is formed having a variation in stoichiometry.

24. The structure of claim 19 , wherein the phase change material gradient is formed from at least one chalcogenide alloy having a variation in a stoichiometric contribution of at least one of a number of elements of the chalcogenide alloy to form the gradient.

25. The structure of claim 24 , wherein the gradient is formed having an increase in the stoichiometric contribution of at least one of the number of elements from a region adjacent to the first electrode to a region adjacent to the second electrode.

26. The structure of claim 24 , wherein the gradient is formed having a decrease in the stoichiometric contribution of at least one of the number of elements from a region adjacent to the first electrode to a region adjacent to the second electrode.

27. The structure of claim 24 , wherein the gradient is formed having an increased or decreased stoichiometric contribution of at least one of the number of elements between a region adjacent to the first electrode and a region adjacent to the second electrode relative to the region adjacent to the first electrode and the region adjacent to the second electrode.

28. A memory cell structure, comprising:

a storage element material of a memory cell and a select device material of the memory cell arranged in series between a first electrode and a second electrode;

a third electrode formed between the storage element material and the select device material; and

a phase change material gradient in at least one of the storage element material and the select device material.

29. The structure of claim 28 , wherein at least one of the storage element material and the select device material comprises a chalcogenide.

30. The structure of claim 29 , wherein at least one of the storage element material and the select device material is formed with at least one chalcogenide alloy having a variation in stoichiometry.