Apr 15, 2009
Fluorescent particles map temperature on the nanoscale
Scientists in France are developing nanoscale scanning thermal sensors by gluing fluorescent particles to the end of atomic force microscope tips. These nanothermometers combine a high lateral resolution with good temperature sensitivity and can monitor the heating of micro- and nano-devices powered by electrical currents.
When fluorescent materials are heated by an external excitation, their light emission intensity generally diminishes and can be completely quenched if the temperature becomes too high. This effect can be used to develop new kinds of thermal sensors for determining the temperature of the local environment.
To make its movable thermal sensor, the team glues a small fluorescent particle at the end on a sharp atomic force microscope tip. The particle consists of fluoride glass doped with erbium and ytterbium ions. To determine the local temperature, the instrument compares the intensity of two visible emission lines that come from levels in thermal equilibrium.
The images above show the topography and the temperature map of a nickel stripe heated by a 6 mA DC electrical current. The stripe is 1 µm wide and 40 µm long. The temperature map is reconstructed using the fluorescence images of the particle employed to scan the device. The value of the temperature is in good agreement with a finite element method simulation.
Such a technique is very promising for the thermal characterization of micro- and nano-electronic devices and for studying the heat transfer between nanostructures. It can also operate under AC electrical currents and in a liquid environment.
The researchers presented their work in Nanotechnology.
About the author
The thermal experiments were performed at the Ecole Superieure de Physique et de Chimie Industrielle de la Ville de Paris (ESPCI) in France, in a laboratory jointly financed by the Centre National de la Recherche Scientifique (CNRS), the Université Pierre et Marie Curie (UPMC) and the ESPCI. Elika Saïdi is a PhD student working on the thermal properties of nanoheaters. Benjamin Samson just defended his PhD on nanothermics and heat transfer studies. Lionel Aigouy is the head of the team also composed of Loïc Lalouat who is working on nanoplasmonics and nanothermics. The work has been performed in collaboration with Dr Peter Löw and Christian Bergaud from the Laboratoire d'Architecture et d'Analyse des Systèmes in Toulouse, with Dr Sebastian Volz from the Ecole Centrale de Paris and with Dr Michel Mortier from the Ecole Nationale Supérieure de Chimie de Paris.