Temperature dependence of the optical energy gap for the CdSxSe1−x quantum dots

A temperature dependence of the optical energy gap E g (T) for the CdSxSe1−x quantum dots synthesized in a borosilicate glass matrix was investigated in the range of 4.2–500 K. It was demonstrated that this dependence reproduced the dependence E g (T) for bulk crystals and is described by the Varshni formula for r > aB over the entire temperature range. Here, r is the average dot radius, and a B is the Bohr radius for the exciton in a bulk crystal. With the transition to quantum dots with r > aB , a decrease in the thermal coefficient of the band gap and a deviation from the Varshni dependence were observed in the temperature range of 4.2–100 K. The specific features observed are explainable by a decrease in the resulting macroscopic potential of the electron-phonon interaction and by modification of the vibration spectrum for dots as their volume decreases.