Structural and electrical studies of conductive nanowires prepared by focused ion beam induced deposition

Abstract

Articles you may be interested inResistivity change of the diamondlike carbon, deposited by focused-ion-beam chemical vapor deposition, induced by the annealing treatment Conductive nanowires were deposited by a focused gallium ion beam using W͑CO͒ 6 and ͑CH 3 ͒ 3 CH 3 C 5 H 4 Pt as precursors. An in situ electrical treatment can substantially modify the structure and resistivity of these nanowires. This treatment consists in applying voltage ramps to the wire, leading to a high current density that induces wire annealing. The nanowires are deposited by focused ion-beam-induced deposition on two kinds of customized supports based on diamondlike carbon or Si 3 N 4 membranes, particularly suitable for electrical tests and transmission electron microscopy characterization. In the case of tungsten wires, the treatment induces an improvement of the resistivity due to both gallium contamination removal and wire crystallization, which occurs at high temperature. The treatment leads to low-resistivity ͑50 ⍀ cm͒ polycrystalline tungsten nanowires. For platinum wires, the treatment induces an increase of resistivity. In fact, this treated wire was composed of conductive droplets ͑platinum and PtGa 2 ͒ connected by a wire with poor conductivity.

Electric field induced motion of metallic droplets: Application to submicron contactor

“…A gallium droplet, which has been formed at one extremity of a wire, as explained previously [5][6] , migrates towards the opposite terminal if the voltage is reversed. The droplet is always driven towards the lowest potential electrode when the voltage applied (~2.5V) induces a current density of about 1.4x10 7 A/cm 2 through the tungsten wire.…”

“…Tungsten nanowires (200nm wide by 80nm thick) has been fabricated following a focussed ion beam induced deposition process [5][6] (FIBID) from dissociation of WC0 6 molecules and studied in our cross beam system equipped with in situ electrical measurements. A current density above a threshold value [5][6] of 1.4x10 7 A/cm 2 induces a wire annealing by Joule effect which improves their electrical conductivity. The high current density induces the exudation of gallium out of the wire, and its merging as several droplets (Fig.…”

“…Increasing the voltage up to 4V drives all the droplets towards the lowest potential electrode, leading to the formation of a unique droplet of about 550nm in diameter (SEM image inserted on Fig 1). For voltage above 4V, the resistance of the wire drops due to the non reversible crystallisation of the tungsten wire [5][6] .…”

“…One can note that gallium atoms move in opposite Such spherical pure gallium droplets have been already observed on structures prepared with gallium + FIB 7 . We have checked that the volume of the droplet corresponds to the amount of gallium + ions implanted in the tungsten wire [5][6] during the deposition process. The electrical treatment alters the initial mixture of tungsten and gallium, and leads to the separation of the two components according to the phase diagram 8 .…”

“…Since the droplet is made of at least 90at% of gallium [5][6] , it is conductive and may be used to establish a contact between two electrodes separated by a distance of the order of the size of the droplet. Such a liquid contactor may be switched on and off by applying an electric field to position the droplet inside or outside the gap between the two electrodes.…”