Thermal stability of Pt nanowires manufactured by Ga+ focused ion beam (FIB)
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Thermal stability of Pt nanowires manufactured by Ga+ focused ion beam (FIB) B.J. Inkson1 and G. Dehm2 1 Dept. of Engineering Materials, Sheffield University, Mappin Street, Sheffield S1 3JD, U.K. 2 Max-Planck-Institut für Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart, Germany
ABSTRACT Pt nanowires have been produced by FIB deposition of Pt thin films in a commercial Ga+ focused ion beam (FIB) system, followed by cross-sectional sputtering to form electron transparent Pt nanowires. The thermal stability of amorphous FIB manufactured Pt wires has been investigated by in-situ thermal cycling in a TEM. The Pt wires are stable up to 580-650°C where partial crystallization is observed in vacuum. Facetted nanoparticles grow on the wire surface, growing into free space by surface diffusion and minimising contact area with the underlying wire. The particles are fcc Pt with some dissolved Ga. Continued heating results in particle spheroidization, coalescence and growth, retaining the fcc structure.
INTRODUCTION Sub-micron metallic wires are crucial components of modern electronic and MEMS devices. As wire dimensions reduce to the nanometre regime, their mechanical and thermal properties change due to factors such as an increased surface area to bulk volume ratio. Restricted volume alters possible stress states, increases surface contamination effects, increases the influence of the wire substrate and 'confines' dislocations altering mechanisms of plastic deformation [1-3]. Focused ion beam (FIB) microscopes are being increasingly used to deposit, modify and repair sub-micron electronic wires/interconnects both on the production line, and off-line as a method of modifying complex circuits for diagnostic reasons. A number of different metals and insulators can be deposited by FIB deposition to form wires, including Pt, Au, W and SiO2 [4-7]. Pt films are frequently used as electrode contacts, and amorphous Pt films and wires deposited by FIB can be used to repair interconnect failures and as protective capping layers in FIBmachined nanodevices. Thermal stability is a major issue to consider when using FIB manufactured components in devices which will be subject to thermal cycling. In this study the thermal stability of amorphous Pt-based nanowires manufactured by FIB processing have been investigated. To characterize the dynamical mechanisms of microstructural changes during thermal cycling, FIB-machined Pt wires were thermally cycled in-situ in a TEM over the temperature range 25-750ºC and microstructural changes were recorded on video using a television rate camera.
EXPERIMENT 500 to 1000nm-thick Pt-based films of area 10µm x 20µm were deposited on Cu and Ccoated Ti-Al2O3 substrates in a FEI 200TEM FIB workstation by breakdown of (trimethyl)methylcyclopentadienylplatinum (CH3)3(CH3C5H4)Pt gas [4,7] using a focused 100pA Ga+ beam
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