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) over bar > a(B) over the entire temperature range. Here, (r) over bar 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) over bar < a(B), 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. (C) 2002 MAIK "Nauka / Interperiodica".