CdI 2 and BiI 3 can be made solid solution by quench deposition over the full range of concentration ratio. On annealing of the solution, two-dimensional small clusters of BiI 3 are produced which are coupled to the lattice of CdI 2 host matrix and show confined-exciton absorption. There is too large a barrier for Bi 3þ ions to aggregate to form larger BiI 3 clusters because the aggregation requires two Bi 3þ ions to migrate in a pair in two dimensions. The present experiment opens up the possibility of a method for achieving designed small BiI 3 clusters embedded in the CdI 2 crystal matrix at high densities, with the clusters directly coupled to the lattice of the host matrix.

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