The growth of thin films made from Samarium-doped alkaline earth fluoro halides (AEFH) of compositionSrxCa1−xFCl:Sm2+(0⩽x⩽1)is presented and the possibilities are studied to increase significantly the inhomogeneous width of theSm2+optical zero phonon transitions. The best films were obtained when grown with a molecular beam deposition (MBD) method involving two separate molecular beams: one for the alkaline earth fluoride, the other one for the alkaline earth halide (Cl or Br). The results demonstrate that the double beam MBD technique employed is able to produce pure and mixed Matlockite films with targeted composition. The results of mainly optical studies of the samariumf–ftransitions and of other complementary techniques are used to assess the composition and homogeneity of the films. With the aid of a model the composition dependence of the positions of specific opticalf–femission lines is established. Their inhomogeneous linewidth is compared with that of corresponding emission lines obtained from bulk samples of the same chemical composition. The linewidths of the films are only slightly larger (∼1.5–2times). Thus, the film morphology cannot be exploited to increase substantially the inhomogeneous broadening of the luminescence lines. A novel approach to increase this broadening was devised, theoretically modeled and successfully tested by using multilayered sandwich-type thin films in conjunction with interdiffusion. Films with cation disorder of compositionSrxCa1−xFCl(x=0.5 /0/ 0.5/ 0/..)were grown. The5D1→7F0Sm2+emission linewidth is thereby increased to70 cm−1full width half maximum. A width of100 cm−1may be obtained within the composition rangex=0,x=1.This represents an enhancement by a factor of 3–5 in comparison with the largest values obtained in appropriate mixed bulk AEFH of constant composition. A factor>50is gained in comparison with pure bulk AEFH hosts. The room temperature (RT) homogeneous linewidths, on the other hand, are similar to those found in bulk mixed crystals of constant composition. The intrafilm host cation diffusion during film growth of the sandwich structures was further studied. A diffusion constant of2⋅10−19 m2 s−1for the Sr and Ca ions was deduced from this observation. These films are among the most promising materials for optical mass data storage through RT hole burning. ©1997 American Institute of Physics.