Texture Analysis of LiF Thin Films Evaporated onto Amorphous Substrates at Different Temperatures

Polycrystalline thin LiF films thermally evaporated on amorphous substrates show different crystallite orientations depending on the substrate temperature during evaporation. The recording of direct diffraction pole figure shows that the LiF crystallites present a single crystal texture, which can be described as a (522) [uvw] texture for high temperature deposition (250 to 300°C) and as (16 9 7) [uvw] texture for low temperature (room temperature) substrates. Scanning electron microscopy shows the presence of a globular film structure both for high and low temperature depositions with an average grain size of about 200 to 250 and 130 to 150 nm for high and low temperature evaporations, respectively. By rising the deposition temperature the (100) LiF crystallographic direction approaches the normal to the substrate plane with an increase of the film refractive index.