An influence of (Cdi)n metallic clusters on the optical absorption and phonon spectra of CdI2 crystals was studied. Metallic clusters of spherical shape were formed during the growth of non-stoichiometric crystals. Radii of clusters are in range from 10 to 500 nm according to scanning electron microscopy (SEM) data. The density of clusters was estimated from fractal dimension calculations. The fractal dimension of (Cdi)n clusters has been found to be varied from 1.488 to 1.793. In the framework of Mie theory the spectral and size dependencies of extinction coefficients were calculated. From the experimentally obtained spectra it is evident that the metallic clusters are responsible for the bands in the transparency region of CdI2 crystals (360–430 nm) and for the peaks in the mid-infrared absorption spectra which are not present in the spectra of pure cadmium iodide. The nature of this additional optical and infrared absorption is concerned with the bulk and surface plasmons and the surface phonon modes of metallic clusters, respectively.
Radiation Measurements, 2007, vol.42, pp. 851-854.

Abstract. The influence of overstoichiometric Cdi atoms on the optical properties of cadmium iodide layered crystals has been investigated. The results of optical absorption, luminescence, and luminescence excitation studies of CdI2 crystals with controlled deviation from stoichiometric composition allow observing correlations between the Cdi concentration and features in absorption and emission spectra up to concentrations of 10#18 cm−3. At higher concentrations the overstoichiometric cadmium atoms form clusters, which were observed using scanning electron microscopy. The extinction spectra of (CdIi)n clusters are calculated in the frame of Mie theory and are found to correlate with the optical studies.
J. Phys.: Condens. Matter 19 (2007) 395015 (9pp)