Thermal instability of nanowires

On the way to physical nanowire implementation and device fabrication, both chemical and thermal stability of the nanowires should be carefully analyzed. Due to their extremely high surface-to-volume-ratio, nanowire properties are expected to be influenced by adsorbates, surface chemical modifications, and morphological changes at elevated temperatures.

Recently, our group demonstrated that metal nanowires are transformed into chains of nanospheres during annealing due to the Rayleigh instability.

The driving force of this process is the minimization of surface energy of the initial wire. Both sphere size and spacing between adjacent spheres depend on the initial wire diameter, material, and crystallinity of the wire. First, the Rayleigh instability of copper nanowires was experimentally demonstrated. After annealing 30–50 nm diameter wires at temperatures between 400 and 600°C, different stages of the fragmentation process were observed by scanning electron microscopy. At 400 °C, the wires started to fragment, forming shorter sections at 500 °C, and finally decaying into a chain of nanospheres at 600 °C. Average diameter and spacing of the spheres were in agreement with theoretical predictions. Experiments performed on poly- and on [110] textured single-crystalline gold nanowires on SiO2 substrates evidenced that the single-crystalline wires are more stable than the polycrystalline ones. Under the same annealing conditions, single-crystalline wires maintained their morphology for longer times (approximately a factor two in the case of nanowires with diameters around 100 nm).

Recent Publications

1. Influence of crystallinity on the Rayleigh instability of gold nanowires S. Karim, M.E. Toimil-Molares, W. Ensinger, A.G. Balogh, T.W. Cornelius, E.U. Khan, R. Neumann Journal of Physics D- Applied Physics 40 (2007) 3767

2. Morphological evolution of Au nanowires controlled by Rayleigh instability S. Karim, M.E. Toimil-Molares, A.G. Balogh, W. Ensinger, T.W. Cornelius, E.U. Khan, R. Neumann Nanotechnology 17 (2006) 5954

3. Fragmentation of nanowires driven by Rayleigh instability M.E. Toimil-Molares, A.G. Balogh, T.W. Cornelius, R. Neumann, C. Trautmann Appl. Phys. Lett. 85 (2004) 5337