Universitat Autònoma de Barcelona (UAB) and
Catalan Institute of Nanoscience and Nanotechnology (ICN2)
Javier Rodríguez-Viejo is Full Professor of Applied Physics at the Autonomous University of Barcelona (Universitat Autònoma de Barcelona, UAB) and leads the Group of Thermal Properties of Nanoscale Materials at the UAB and the ICN2.
He performed the experimental part of his doctoral thesis at the Institut des Materiaux et Procedés CNRS, France and received his PhD in Physics from UAB in 1992. He continued his studies as a postdoctoral researcher at the Massachusetts Institute of Technology, working with Prof. Klavs F. Jensen (Chemical Eng. and Material Science Dep.) and Prof. M.G. Bawendi (Chemistry Dep.) on the synthesis of highly-luminescent CdSe(ZnS) quantum dots and the deposition of thin film quantum dot composites by electrospray organometallic chemical vapor deposition. His research in this field resulted in several patents and papers, one of which is among the most highly cited papers in semiconductor nanoparticles. In May 1997 he was appointed Associate Professor of Applied Physics at the Physics Department of UAB and in 2011 became Full Professor at the same university. He has been visiting scientist at Air Products in Allentown, US (July-August 2008) and Harvard University (May-September 2016).
Nanostructuration, phonon conductance, thermal conductivity
Thermal transport in nanostructured and disordered systems
I will present several examples in which nanostructuration and/or disorder play a relevant role in phonon conductance. The first case is devoted to 3ω measurements in SiGe graded superlattices and how these materials can efficiently suppress phonon transmission across the whole spectrum by simultaneously incorporating scattering mechanisms present in SLs and alloys. The effect is remarkable and has been used to reduce the thermal conductivity below the thin film alloy limit even for thick superlattices with long SL periods
. Then I will show measurements on Si ultrathin membranes and porous Si nanowires using suspended structures. In the case of the NWs we observe a dependence of the thermal conductivity on the diameter and link this observation with the anisotropic etching that occurs during their fabrication
. The last example is devoted to the study of thermal transport (both in-plane, 3ω -Volklein and out-of-plane, 3ω) in disordered organic materials
. I will show that the molecular packing anisotropy that exist in vapor-deposited thin film glasses of an organic semiconductor has a strong impact on heat propagation. In all three examples experimental data is contrasted with molecular or lattice dynamics simulations to unveil the microscopic origin of heat transport.
 Ferrando-Villalba et al. Nano Research 8, 2833-2841 (2015) & The Journal of Physical Chemistry C 124, 36, 19864–19872, 2020.
 Ferrando-Villalba et al. Scientific reports, 8(1), 12795 (2018).
 Ràfols-Ribé et al. Phys. Rev. Mat. 2(3), 035603, (2018) & Ferrando-Villalba, et al. Phys. Rev. Appl. 12(1), 014007, (2019).