Photoluminescence from CdS nanocrystals fabricated by sequential ion implantation

We have studied photoluminescence (PL) spectrum and dynamics of CdS nanocrystals fabricated by sequential Cd+ and S+ ion implantation into Al2O3 matrices. Two peaks related to free excitons of hexagonal CdS are observed in the absorption spectrum at low temperatures. The broad and efficient PL band appears near the absorption edge. The spectral shape of the PL band depends on the excitation laser intensity. Our results show that the observed PL band consists of free-exciton emission and shallow-impurity emission.