1. A memory cell comprising: a first conductive layer operable as an electrode; a second conductive layer operable as an electrode; a semiconductor layer between the first conductive layer and the second conductive layer; wherein the semiconductor layer comprises a first sub-layer, a second sub-layer, and a third sub-layer such that the second sub-layer is disposed between the first sub-layer and the third sub-layer; wherein the first sub-layer and the third sub-layer comprise titanium oxide; and wherein the second sub-layer comprises hafnium oxide; and a barrier layer between the second conductive layer and the semiconductor layer; wherein the barrier layer chemically isolates the second conductive layer from the semiconductor layer; and wherein a work function of the first conductive layer is higher than a work function of the second conductive layer.