Nanometers

Nanometer, symbol nm, is a unit of length in the metric system equal to one billionth of a meter (10^-9 m). The name comes from nano-, the SI prefix meaning 10^-9. In practice, nanometer is used to describe objects whose dimensions lie in the nanoscale, typically 1 to 100 nm.

The nanometer is widely used in science and engineering. In electronics, semiconductor technologies express feature sizes in nanometers, with recent transistors and interconnects built at the few-nanometer scale (for example, gates of about 5–7 nm). In materials science, nanometer-sized particles, thin films, and coatings are common. In biology and chemistry, many macromolecules and viral particles have dimensions measured in nanometers; for instance, DNA double helix diameter is about 2 nm, and many viruses range from tens to a few hundred nanometers. Wavelengths of visible light (roughly 380–750 nm) set a practical limit on optical resolution at ambient conditions.

Measuring and imaging at the nanometer scale relies on advanced instruments. Transmission electron microscopes, scanning electron microscopes, and atomic force microscopes can resolve features well below 10 nm. Nanometer-scale properties often differ from bulk material due to quantum effects and higher surface-area-to-volume ratio, influencing electrical, optical, and chemical behavior.

See also: angstrom, micrometer, nanotechnology, quantum confinement.