Composite organic-inorganic coatings are realized by ion beam sputtering (IBS) from a zone target consisting of PTFE and Al2O3. The composition of the sputtered coatings is measured by Energy-Dispersive X-ray spectroscopy and the molecular structure is analyzed by Fourier Transform Infrared spectroscopy. The variation of the refractive index and the optical quality in dependence of the carbon-fluorine content for different material compositions is investigated. Furthermore, the intrinsic stress of the coatings is analyzed and a change from compressive to tensile stress in dependence of the composition is observed. The production of ion beam sputtered composite coatings with low refractive index and tensile stress is demonstrated.