Confined acoustic phonons in Si membranes

C. M. SOTOMAYOR-TORRES; P.-O. CHAPUIS; F. ALZINA; N. KEHAGIAS; L. SCHNEIDER; E. CHAVEZ; T. KEHOE; A. SHCHEPETOV; M. PRUNNILA; C. RIBÉREAU- GAYON; S. LAAKSO; J. AHOPELTO; J. JOHNSON; A. A. MAZNEV; J. ELIASON; A. MINNICH; K. COLLINS; G. CHEN; K. A. NELSON; A. BRUCHHAUSEN; M. HETTICH; O. RISTOW; T. DEKORSY

Poitiers

Conferencia; Eurotherm seminar 91 - Microscale heat transfer III; 2011

Institut P’ Université de Poitiers

Confined acoustic phonons have been invoked in the explanation of thermal conductance in condensed matter tin attempts to explain experimental results in, eg., Si, xx metals both bulk and microstructures. The predictions of Hicks and Dresselhaus of the dominant role of dimensionality in the thermoelectric figure of merit ZT spun renewed interest in the study ofconfined acoustic phonons. The theoretical background on the origin of these modes triggered inelastic light scattering studies. Perhaps the most unambiguous observations of confined acoustic phonons in Si nanostructures were those in sub 40 nm thick SOI membranes which showed acoustic phonons in low frequency Raman scattering, the frequencies of which increased with decreasing membrane thickness. The observationsand spectral simulation of these membranes and multilayer structures were first explained in the frame of the photo-elastic model. However, the mode order and the type of observed confined acoustic phonons needed extended measurements and calculations of the dispersion relations of these phonons in a range of membranes thickness as well as time-resolved spectroscopy.