The composition of SrF2thin films deposited on carbon plates by sublimation under ultrahigh vacuum has been investigated mainly by Rutherford backscattering (RBS) of &agr; particles as a function of the substrate temperature during the condensation phase and of the thickness of the layers. It is shown that forTS= 270 °C the obtained films are stoichiometric, homogeneous, and quasi‐insensitive to air exposure. The structure of such layers grown on (100)InP single crystals has been deduced from the study of channeling phenomenon. It is demonstrated that the RBS minimum yield &khgr;min, measured on SrF2, decreases with increasing thin‐film thickness, varying from 100 to 400 nm. For a 400‐nm‐thick SrF2thin film at 350 nm from the interface &khgr;min=0.05 showing that the layer is well crystallized and presents the same orientation as the substrate.