Quantum size effects in the luminescence of thin lead sulfide films in PbS-EuS superlattices

The luminescence of very thin (down to 4 nm) ObS films in EuS-PbS superlattices with PbS potential well and EuS barrier thickness ranging from 1 to 20 nm is investigated. It is found that the lead sulphide luminescence band at 80 K may shift by 240 to 440 MeV depending on the thickness of the PbS layers and their deformation by the KCl substrate and EuS layers. Most of the shift can be ascribed to a change in the size quantization level by 20 to 200 MeV upward in energy relative to the edge of the conductivity band