Abstract: A switch is used in circuits which interact with electromagnetic radiation. The switch includes a substrate for supporting components of the switch. A first conductive element on the substrate is provided for connecting to a first component of the circuit, and a second conductive element on the substrate serves to connect to a second component of the circuit. A switch element is made up of a switching material on the substrate and connects the first conductive element to the second conductive element. The switching material is a compound which exhibits a bi-stable phase behavior and is switchable between a first impedance state value and a second impedance state value upon the application of energy thereto. A circuit consisting of a plurality of conductive elements includes the switch for varying current flow which has been induced by the application of electromagnetic radiation.