In this schematic image, a silicon nanowire is shown surrounded by a stack of thin layers of material called dielectrics, which store electrical charge. NIST scientists determined the best arrangement for this dielectric stack for the optimal construction of silicon nanowire-based memory devices. A nanowire is a nanostructure, with the diameter of the order of a nanometer. It can also be defined as the ratio of the length to width being greater than 1000. Alternatively, nanowires can be defined as structures that have a thickness or diameter constrained to tens of nanometers or less and an unconstrained length. A dielectric material (dielectric for short) is an electrical insulator that can be polarized by an applied electric field.