Thin films were grown by vacuum co-evaporation of CsI and PbI 2 compounds from two independent crucibles. X-ray diffraction spectroscopy revealed formation of CsPbI 3 and Cs 4 PbI 6 nanoaggregates in the thin film samples and gave an estimate of their volume percentage as well. It provided also the grain size estimates, which were compared with direct observation of a thin film surface by atomic force microscopy. The absorption, luminescence and decay kinetics characteristics of thin films grown were measured. The optical characteristics of the mentioned ternary nanoaggregates were determined and compared with those of CsPbX 3 and Cs 4 PbX 6 (X = Cl, Br) bulk structures.

Single crystals of PbW04 (PWO) are intensively studied in the last few years in connection with their potential application for scintillation detectors in high energy physics [I, 21. Within the last year a dramatic increase of this research activity has been observed [3] in connection with the planned construction of a PWO-based electromagnetic calorimeter in the accelerator ring at CERN. The emission spectrum of PWO consists of two main componentsthe blue one peaking at about 420 nm and the green one peaking at about 480 to 510 nm. While the blue component is ascribed to the regular lattice centres (w04)2-[4], the green one is related to the WOs centres [ 5 ] , i.e. it depends on the oxygen non-stoichiometry in the crystal and on the concentration of accidental impurities as well. Variable oxygen defi-') Cukrovarnicka 10, CZ-16200 Prague, Czech Republic. *) Rudower Chaussee 6,

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