The present invention provides an apparatus and a method of fabricating the apparatus. The apparatus comprises a substrate having a planar surface and first and second electrodes located on the planar surface. The first electrode has a top surface and a lateral surface, and the lateral surface has an edge near or in contact with the substrate. An electrode insulating layer is located on the top surface and a self-assembled layer located on the lateral surface. The second electrode is in contact with both the self-assembled layer and the electrode insulating layer.