Feb 1, 2007
Silicon nanowires with gold droplets suit tip enhanced Raman spectroscopy (TERS)
Despite widespread research, today's TERS suffers from a lack of defined and reproducible AFM tips with gold nanoparticles to govern the Raman signal enhancement effect. State-of-the-art sputtering of gold layers on conventional AFM tips yields gold nano particles. They form randomly on the tip surface in all sorts of odd shapes. If nanowires with hemispherical gold droplets on that formed by the vapor-liquid solid growth mechanism are welded to AFM tips, the size and shape of the gold nano-droplet is entirely controllable. In the future we intend to make use of this advantageous fabrication of TERS tips to develop TERS for solid-state spectroscopy. This will allow for the detection, for example, of internal stresses in materials with a spatial precision on the nanometer scale.
Potential applications of this novel nanowire-based TERS solution reside especially in the fields of bio-medical, life sciences and security. Important applications are also expected in solid-state research, e.g. in silicon technology where the detection of materials composition, doping, crystal orientation and lattice strain can be probed by Raman spectroscopy.
We are looking forward to exploiting our novel nanowire-TERS tips in interdisciplinary collaborations in the aforementioned fields. It is our aim that based on this technique it will be possible to locally measure the built-in strain in a transistor that makes use to straining silicon at levels close to one-tenth of the theoretical strength of silicon. How this could potentially work is shown in the figure.
About the author
Silke Christiansen is a junior research group leader at the Martin-Luther University and the Max-Planck Institute of Microstructure Physics (department of Ulrich Gösele) in Halle, Germany.
Michael Becker is a postdoc in this group and is in charge of the development of the nanowire-based TERS technique.