Thermal stability of Ti and Pt nanowires manufactured by Ga+ focused ion beam.

Ti and Pt nanowires have been produced by ultra high-vacuum molecular beam epitaxy deposition of Ti thin films and focused ion beam (FIB) deposition of Pt thin films, followed by cross-sectional FIB sputtering to form electron-transparent nanowires. The thermal stability of the nanowires has been investigated by in situ thermal cycling in a transmission electron microscope. Epitaxial single crystal Ti nanowires on (0001)Al(2)O(3) substrates are microstructurally stable up to 550-600 degrees C, above which limited dislocation motion is activated shortly before the Ti-wires oxidize. The amorphous FIB-deposited Pt wires are stable up to 580-650 degrees C where partial crystallization is observed in vacuum. Faceted nanoparticles grow on the wire surface, growing into free space by surface diffusion and minimizing contact area with the underlying wire. The particles are face-centred cubic (fcc) Pt with some dissolved Ga. Continued heating results in particle spheroidization, coalescence and growth, retaining the fcc structure.