Nanoscale growth of (Zn,Sr)S system for electron-trapping optical memories

In this work, we give a review on the nanoscale cubic-islands growth of SrS and ZnxSr1-xS [abbreviated as (ZnSr)S] thin films by solid-source molecular-beam epitaxy (MBE). Our detailed analyses of scanning electron microscopy (SEM) and atomic force microscopy (AFM) images show that different sizes of SrS islands can be achieved depending on the substrate temperature. Reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) establish cube-on-cube (001)SrS " (001)MgO with [001]SrS " [001]MgO epitaxial relationship. All these results point towards the growth to occur in step-flow mode. When (ZnSr)S is codoped with europium and samarium ions (SrS : Eu, Sm and ZnSrS : Eu, Sm), infrared-stimulated luminescence (ISL) with a peak at 612 nm is observed at room temperature, which is stimulated with infrared light after irradiation with visible light. The ISL results show that the (ZnSr)S system can be developed for erasable and rewritable optical memory.