Some embodiments include a method of forming a memory cell. A first portion of a switching region is formed over a first electrode. A second portion of the switching region is formed over the first portion using atomic layer deposition. The second portion is a different composition than the first portion. An ion source region is formed over the switching region. A second electrode is formed over the ion source region. Some embodiments include a memory cell having a switching region between a pair of electrodes. The switching region is configured to be reversibly transitioned between a low resistive state and a high resistive state. The switching region includes two or more discrete portions, with one of the portions not having a non-oxygen component in common with any composition directly against it in the high resistive state.
1. A memory cell, comprising:
a switching region located between a pair of electrodes, the switching region having a thickness of from about 6 angstroms to about 20 angstroms and comprising a first discrete portion and a second discrete portion, with the first discrete portion having a thickness within a range of from greater than 0 angstroms to less than 20 angstroms, each of the first discrete portion and the second discrete portion not having a non-oxygen component in common with any composition directly against the corresponding discrete portion in a high resistive state of the memory cell, each of the first discrete portion and the second discrete portions being formed by a deposition process, and at least one of the first and second discrete portions being formed by atomic layer deposition, each of the first discrete portion and the second discrete portion not having a non-oxygen component in common with any composition of any adjacent layers directly against the corresponding discrete portion.
2. The memory cell of claim 1 wherein one of first and second discrete portions is thicker than the other.
3. The memory cell of claim 1 wherein one of the first and second discrete portions of the switching region comprises one or more of aluminum, hafnium, silicon, titanium and zirconium.
4. The memory cell of claim 1 wherein one of the first and second discrete portions of the switching region has a thickness of less than one monolayer.
5. The memory cell of claim 1 wherein:
the first discrete portion consists of oxygen in combination with one or more transition metals; and
the second discrete portion consists of oxygen in combination with one or more non-transition elements; wherein said non-transition elements are selected from the group consisting of metals, semi-metals, alkaline earth elements, and mixtures thereof.
6. The memory cell of claim 1 wherein:
the first discrete portion consists of oxygen in combination with one or more non-transition elements; wherein said non-transition elements are selected from the group consisting of metals, semi-metals, alkaline earth elements, and mixtures thereof; and
the second discrete portion consists of oxygen in combination with one or more transition metals.