Purification and crystallization of tungsten wires fabricated by focused-ion-beam-induced deposition

Abstract : We studied the behavior of tungsten wires, fabricated by focused-ion-beam-induced deposition and subjected to high current density. We present a simple electrical treatment, which allows an improved wire resistivity of more than 80%. We have distinguished two steps in the treatment. When the current density reaches 1.4x107 A/cm2, Ga atoms segregate and form droplets on the wire. As the current density increases, new droplets appear and merge into a single droplet. At 5.8x107 A/cm2, the droplet evaporates, the resistance is lost and the wire crystallizes. The final resistivity is close to 55 µV cm. The same treatment applied to as-deposited platinum wires does not lead to the same observations: neither segregation nor crystallization was found.