OPTICAL-PROPERTIES OF NANOSTRUCTURES IN LAYERED METAL TRI-IODIDE CRYSTALS

The optical response of excitons confined in characteristic nanostruct ures in layered metal tri-iodide crystals introduced by some irregular stackings from the bulk structures is reviewed. In BiI3 a specific st acking fault takes place during crystal growth constructing macroscopi c planar defects. In this space conspicuous localized exciton transiti ons occur below the intrinsic absorption edge. Another stacking disord er introduced by applying external stress in this crystal brings about a new nanostructure domain of symmetry D-3d different from that of bu lk symmetry C-3i(2). The optical transitions due to new structures app ear in the lower energy region as an absorption and luminescence line series. The similar nanostructures are induced in SbI3 crystals under the hydrostatic pressure. In these nanostructures, the electronic stru cture is analyzed by a model based on the confined excitons in a nanos cale disk-like shape space. The magnetic field effect confirms the str ucture in the wave function-size scale. The nanoscale disk-like struct ure of BiI3 in CdI2 matrices is also obtained by a hot wall technique and mixed crystal annealing, which is realized by observing the size d istribution with an electron microscope. In a BiL(3) disk in CdI2 Stok es shifted photoluminescence bands appear. The Stokes shifts of the lu minescence bands are understood by considering the size-dependent exci ton-phonon interaction. In these nanostructures large optical nonlinea rity under the intense laser field was obtained.