Abstract: An embodiment includes an apparatus comprising: first and second electrodes; first and second insulation layers between the first and second electrodes; and a middle layer between the first and second insulation layers; wherein (a) the middle layer includes material that has a first resistance when the first electrode is biased at a first voltage level and a second resistance when the first electrode is biased at a second voltage level; (b) the first resistance is less than the second resistance and the first voltage level is greater than the second voltage level. Other embodiments are described herein.