Damping of surface acoustic vibration induced by electrons trapped on SnO2 nanocrystal surface

Broad full widths of half maxima (dampings) are observed from the low-frequency Raman spectra of hydrothermally prepared SnO2 nanocrystal congeries. No matrix exists between these nanocrystals and the complex-frequency model is thus unable to explain the damping in the low-frequency Raman peaks. An alternative model in which damping is induced by the interaction between confined surface acoustic vibrations and localized electrons near the nanocrystal surface is proposed to explain the phenomenon. This model which suggests that damping is proportional to d−3/2, where d is the average diameter of nanocrystals, is corroborated by our experimental results.