Research

Nanocalorimetry

The group is largely involved in nanocalorimetric analysis of low dimensional systems aiming to analyze thermodynamics and kinetics playing a role in phase transitions occurring in thin and ultrathin films or nanostructured materials.

We use membrane-based nanocalorimetry at very fast heating rates (104 - 105 K/s), a technique developed by Les Allen at the University of Illinois.

Nanocalorimeter sketch

3D representation of a nanocalorimeter viewed from top and bottom..

Thermal transport and thermoelectricity

Thermal conductivity measurements in thin films (semiconductors,superlattices, oxides) or arrays of nanowires embedded in templates is carried out using home-made 3ω setups. Individual nanowires of different shapes and materials and ultrathin membranes are measured using suspended structures.

Another activity of the group is the micro(nano)fabrication of thermoelectric devices for microgeneration in portable applications.

Suspended structure

SEm image showing a suspended structure employed to measure the thermal conductivity of a 17.5 nm thick monocrystalline layer.

Ultrastable glasses

Since 2008 GNaM is devoted to the study of ultrastable glass formation via vapor-deposition at temperatures in the vicinity of the glass transition temperature. The field started in 2007 with the discovery by Ediger’s group of ultrastability in various pharmaceutical compounds grown from the vapor. This subject is rapidly gaining interest in the glass community and ultrastable glass formation has been extended to many molecules and materials, including small and medium size organic molecules, polymers and metallic glasses. The increased of stability is traced-back to enhanced molecular mobility at the surface. Molecules grown from the vapor have time to explore lower positions of the energy landscape before being buried by other molecules.

Ultrastable glasses of celecoxib

Specific heat capacity of glasses of celecoxib with different stability prepared by PVD.

Campus d'excel·lència internacional U A B