Raman scattering from GaP microcrystals: analysis of the surface phonon peak

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Abstract
The Raman spectra of GaP microcrystals are decomposed into TO, LO an surface phonon (SP) peaks. The deconvoluted SP peak is broad and asymmetric. Its intensity increases rapidly as the particle size decreases. The experimental size dependence of the ratio of the integrated intensities ISP/ITO is compared with theoretical calculation and the importance of the shape effect on this ratio is suggested. The lineshape of the SP is calculated by introducing a simple equation based on the effective-medium theory. By assuming a shape close to ellipsoidal a lineshape is obtained that reproduces the observed asymmetric SP lineshape fairly well.