Pressure dependence of the Raman active vibrations in InP–CdS hybrid nanoparticles

Abstract

AbstractThe effects of pressure on the confined and surface‐optical (SO) vibrations in core‐shell InP–CdS colloidal nanoparticles are explored experimentally by Raman scattering and theoretically using the phenomenological macroscopic approach (PMA) (F. Comas and C. Trallero‐Giner, Phys. Rev. B 67, 115301 (2003); C. Trallero‐Giner et al., to be published [1]). Experiments on two sample ensembles are carried out to P = 6.5 GPa at 373 K and 230 K (including laser heating) using diamond‐cells with 4:1 methanol:ethanol and pyridine media. We observe the pressure‐induced shifts of the peaks due to the confined LO‐ and TO‐like core modes, and of the broad feature assigned to SO vibrations at the CdS‐shell surface. PMA calculations are performed for the confined modes and the ℓ = 1, 2 SO modes in spherical geometry using pressure‐dependent bulk parameters as input. We compute the frequencies for different core radii and shell‐to‐core radius ratios γ. The best fit to the pressure data is found for an InP core diameter of 45 ± 10 A, and γ ∼ 1.1–1.4 depending on the sample ensemble and the value of ℓ. The effects of pressure on the InP–CdS core‐shell modes appear to be well described by the PMA formalism. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)