Line-shape and lifetime studies of exciton luminescence from confined CuCl thin films

Photoluminescence studies have been performed on structures, grown by molecular-beam epitaxy, with thin films of CuCl (30–1200 Å) confined between layers of ${\mathrm{CaF}}_2$. Excitons were formed by irradiation of these systems with uv frequencies above the CuCl band gap, and the spectral and temporal dependences of the recombination radiation were compared with those of a bulk CuCl single crystal. We employ a kinetic model to explain why the photoluminescence line shapes of the free excitons in the thin films were characteristic of a much hotter exciton temperature and the lifetimes were much shorter (<40 ps) than those of the bulk CuCl crystal (850 ps).