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Published online by Cambridge University Press: 01 February 2011
The large surface to volume ratio in nanometer sized wire structures cause a strong dependence of the optical Raman mode on the thermal conductivity of a surrounding medium. On the basis of optical measurements on silicon nanowires as a function of excitation laser power we explain the very large red-shifted Raman spectra observed already for moderate laser powers. This thermal effect is enhanced by a silicon oxide sheath, rendering a reduced thermal contact of the wires to the substrate. The intrinsic redshift due to spatial confinement in silicon nanowires is found to be smaller than 2 cm−1.