Pressure- and laser-tuned Raman scattering in II-VI semiconductor nanocrystals: Electron-phonon coupling

We report pressure- and laser-tuned Raman-scattering studies on ${\mathrm{CdS}}_{\mathit{x}}$${\mathrm{Se}}_{1\mathrm{-}\mathit{x}}$ nanocrystals. The electron-phonon coupling strength S, known as the Huang-Rhys parameter, was determined as a function of pressure beyond the bulk-phase-transition pressure point. The coupling strength is not drastically smaller, as might be expected theoretically, and also shows no abrupt changes at the bulk-phase-transition pressure point. These results indicate that deep traps play a critical part in the mechanism of the electron-phonon coupling.