Effect of size confinement on photoacoustic spectra and photothermal response of CdSxSe1-x (0 <= x <= 1) nanocrystals in a glass matrix

Photoacoustic (PA) spectroscopy is applied to study an optical absorption o f CdSxSe1-x.(x=0.26) nanocrystals in a glass matrix annealed at 700 degrees C for different time duration. As the annealing time increases, a shift of the absorption peak due to the quantum confinement effect to lower energy i s observed. The average diameters increases from 4.6 to 9.4 nm as the annea ling time increases from 0 to 120 min. The PA signal intensities plotted in the semilogarithmic scale vary linearly below the fundamental absorption e dges. The steepness factor (slope of exponential optical absorption) of the PA spectra increases with increasing annealing time. The ultrafast transie nt lensing (UTL) effect signals showed tri-exponential behavior in the orde r of 1 ps (A), a few ten ps (B), and more than a few hundred ps (C). It was found that the relative of component C increased while that of component B decreases as the size of nanocrystals in a glass matrix decreased.