Metal nanowires and nanogaps

Au nanowires are synthesized by electrochemical deposition in etched ion track membranes. In polycarbonate templates, prepared by heavy-ion irradiation and subsequent etching, Au nanowires with diameters down to 25 nm are electrochemically synthesized. Four-circle X-ray diffraction and transmission electron microscopy measurements demonstrated that wires deposited potentiostatically at a voltage of -1.2 V at 65°C are single-crystalline and oriented along the [110] direction. By reverse-pulse electrodeposition, wires oriented along the [100] direction are grown. The wires are cylindrical over their whole length. The morphology of the caps growing on top of poly- and single-crystalline wires is a strong indication of the particular crystalline structure of the nanowires.

With infrared spectroscopic microscopy using synchrotron light, the resonant light scattering from single metal nanowires with diameters in the 100 nm range and with lengths of a few microns was investigated in collaboration with the group of Prof. A.M. Pucci at the University of Heidelberg. The Au and Cu nanowires were electrochemically grown in polycarbonate etched ion-track membranes and transferred on infrared-transparent substrates. Significant antenna-like plasmon resonances were observed in good agreement with exact light-scattering calculations. The resonances depend not only on length and diameter but also on the dielectric surrounding of the nanowire. The observed maximum extinction at resonance corresponds to an electromagnetic far-field enhancement by a factor of about 5.

Recent Publications

1. Resonant Plasmonic and Vibrational Coupling in a Tailored Nanoantenna for Infrared Detection F. Neubrech, A. Pucci, T.W. Cornelius, S. Karim, A. Garcia-Etxarri, J. Aizpurua, Phy. Rev. Lett. 101 (2008) 157403

2. Resonances of individual metal nanowires in the infrared, F. Neubrech, T. Kolb, R. Lovrincic, G. Fahsold, A. Pucci, J. Aizpurua, T.W. Cornelius, M.E. Toimil-Molares, R. Neumann, S. Karim, Appl. Phys. Lett. 89 (2006) 253104

3. Synthesis of gold nanowires with controlled crystallographic characteristics, S. Karim, M.E. Toimil-Molares, F. Maurer, G. Miehe, W. Ensinger, J. Liu, T.W. Cornelius, R. Neumann, Appl. Phys. A 84 (2006) 403-407

4. Electrochemical fabrication of single-crystalline and polycrystalline Au nanowires: The influence of deposition parameters, J. Liu, J.L. Duan, M.E. Toimil-Molares, S. Karim, T.W. Cornelius, D. Dobrev, H.J. Yao, Y.M. Sun, M.D. Hou, D. Mo, Z.G. Wang, R. Neumann, Nanotechnology 17 (2006) 1922-1926