In a first aspect, a memory cell is provided, the memory cell including: (a) a first conducting layer formed above a substrate; (b) a second conducting layer formed above the first conducting layer; (c) a structure formed between the first and second conducting layers, wherein the structure includes a sidewall that defines an opening extending between the first and second conducting layers, and wherein the structure is comprised of a material that facilitates selective, directional growth of carbon nano-tubes; and (d) a carbon-based switching layer that includes carbon nano-tubes formed on the sidewall of the structure. Numerous other aspects are provided.