The new generation of neutron detectors based on 6LiF thin films has been widely investigated in the last decades. The structure of polycristalline thin films has a significant impact upon their performance in neutron detectors, however the relationship between the physical properties of LiF-based thin films and their performance is still far from being completely understood. A systematic investigation of the role played by the growth conditions on the optical and morphological properties of thermally evaporated 6LiF thin films has been carried out by combining spectrophotometry, stylus profilometry and atomic force microscopy. A clear picture of the influence of film thickness and deposition temperature on transparency, porosity, roughness and grain size of polycristalline 6LiF thin films thermally evaporated on amorphous substrates has been obtained