Raman thermometry: Novel contactless method for thermal conductivity determination
Emigdio Chávez-Angel (Catalan Institute of Nanoscience and Nanotechnology (ICN2), 08193 Bellaterra, Barcelona, Spain)

The miniaturization trend of the technology has led to power level densities in excess 100 W/cm2, which are in the order of the heat produced in a nuclear reactor. The need for new cooling techniques has positioned the thermal management on the stage during recent years. Moreover, the engineering of the thermal conduction opens a route to energy harvesting through, for example, thermoelectric generation. Recent experimental and theoretical reports point to an enhancement of the thermoelectric figure of merit in thin films, nanowires and superlattices, primarily as a result of the decrease of the thermal conductivity compared to the bulk counterpart, without a corresponding decrease in electrical conductivity. The reduced dimensions lead to the confinement of acoustics modes and the discretization of their spectrum, resulting in the modification of phonon density of states and dramatic decrease of group/phase velocity and phonon lifetime [1–3].
In the present work the thickness-dependence of the thermal conductivity of silicon nanomembranes with thicknesses ranging from 9 to 1500 nm is presented. The thermal conductivity of the membranes was investigated by using two novel contactless techniques based on the Raman scattering spectroscopy [4,5].
References
[1] E. Chávez, et al., J. Phys. Conf. Ser. 395, 012105 (2012).
[2] J. Cuffe et al., Nano Lett. 12, 3569 (2012).
[3] J. Cuffe et al., Phys. Rev. Lett. 110, 095503 (2013).
[4] E. Chávez-Ángel, et al., APL Mater. 2, 012113 (2014).
[5] J. S. Reparaz, et al., Rev. Sci. Instrum. 85, 034901 (2014).