Size dependence of electron-LO-phonon coupling in semiconductor nanocrystals.

Abstract

An increase in the Frohlich-electron-LO-phonon interaction strength with decreasing nanocrystal size in the strong confinement limited is reported. This results from the size dependence of resonant Raman scattering by CdSxSe12x nanocrystals embedded in a glass slab. The mean particle radius 20,R ,30 Aincreases monotoni- cally with the position along the slab so that, for each laser line, the resonance has been tuned by scanning the sample with a microprobe. The relative strength between Frohlich and deformation-potential contributions is determined by analyzing the polarization properties of the scattering. @S0163-1829~96!51716-9# Coupling between electronic and vibrational excitations plays a central role in the physics of crystalline materials, e.g., determining their transport properties and the energy relaxation rate of excited carriers. Semiconductor nanocrys- tals as small as a few hundred unit cells make it possible to investigate the electron-phonon interaction beyond the bulk approximation. In this regime, strong quantum-size effects influence the electronic and vibrational states and their coupling. 1 Also, phonon broadening of the exciton linewidth competes with quantization in determining the energy spec- trum, thereby posing an intrinsic limit to the strength of the