Optical absorption spectra in thin films of M{sub}2Ag{sub}(1-x)Cu{sub}xI{sub}3 (M = K,Rb,Cs) solid solutions

摘要

A study is made of the excitonic absorption spectra of solid solutions of the system (KI){sub}2-(1-x)Ag{sub}(1-x)CuI. On the basis of the dependence of the parameters of the excitonic bands on the concentration x, it is established that solid solutions of the type K{sub}2Ag{sub}(1-x)Cu{sub}xI{sub}3 are formed in the range 0≤x≤0.2. Substitution of Ag atoms by Cu atoms in the (AgI{sub}4){sup}(2-) tetrahedra, which form chains in the orthorhombic crystal K{sub}2AgI{sub}3, promotes the formation of quasi-1D exciton bands and spectra of the persistence type, according to the Onodera-Toyozawa classification, with a splitting off of the impurity band from the exciton band. Comparison with the results of studies of the excitonic spectra in solid solutions Rb{sub}2Ag{sub}(1-x)Cu{sub}xI{sub}3 and Cs{sub}2Ag{sub}(1-x)Cu{sub}xI{sub}3 attests to the appearance of the Rashba effect at small x and to qualitative agreement with the Onodera-Toyozawa theory.