Size-dependent temperature variation of the energy gap in lead-salt quantum dots

We observe that the temperature coefficients of electron-hole pair energies (dE/dT) in PbS and PbSe quantum dots depend strongly on the size of the quantum dot. With decreasing size the temperature coefficient of the lowest electron-hole pair energy dE(g)/dT decreases by more than an order of magnitude from the bulk value. The weak temperature dependence found in the strong-confinement limit is expected for atomiclike levels, but has not been observed previously in a semiconductor.