UV absorption due to densely monodispersed two-molecule BiI3 clusters in CdI2 films

Stable two-molecule Bil(3) clusters can densely be monodispersed in Cdl(2) films up to 10 mol% of Bil(3) concentration, by the method of quench deposition and subsequent annealing of the films. The clusters are stoichiometrically embedded in the Cdl(2) crystal matrix. Their absorption spectrum is characterized by an excitonic peak well fitted to an asymmetrical Lorentzian function. Its peak energy (2.503 eV), line broadening (206 meV) and oscillator strength per molecule (0.14) are strongly enhanced due to the effect on the exciton of confinement. The present experiment suggests that there is a possibility of a new method for achieving well-identified, two-dimensional clusters or microcrystals at high densities.