Microbridges

A microbridge is a microscopic bridge-like structure that connects two supports in a microfabricated device. It can function as a mechanical linkage, a thin electronic constriction, or both. The term is used in microelectromechanical systems (MEMS), superconducting electronics, and nanotechnology.

In MEMS, microbridges are slender beams or membranes that span a small gap between anchors. They may act as cantilevers or supported bridges and are used as sensors and actuators. They are typically made from silicon, silicon nitride, or silicon carbide and fabricated by lithography, etching, and thin-film deposition. Lengths range from tens to hundreds of micrometers, thicknesses from a few hundred nanometers to a few micrometers. Resonant frequencies are in the kilohertz to megahertz range and depend on geometry, material, and boundary conditions.

In superconducting electronics, a microbridge is a narrow constriction between two superconductors, forming a weak link. Dayem and other microbridges can function as Josephson junctions, with critical current set by cross section and temperature. They are typically tens to hundreds of nanometers wide and a few hundred nanometers to micrometers long, made from aluminum, niobium, or similar materials. They are used in detectors, quantum bits, and SQUIDs.

Fabrication and characterization use lithography, deposition, and etching. MEMS bridges are characterized by mechanical resonance; superconducting bridges by current–voltage behavior and switching.