In this work, physical and optical properties of ZnS films grown at different evaporation conditions have been
studied. ZnS 3000 nm thick films have been deposited on Ge substrates at 200°C, 120°C and without substrate heating.
In addition, evaporation rates of 4, 2 and 1 nm/s have been considered. The structural and morphological properties of
the films have been analysed by XRD and AFM, respectively and the refractive index in the 2.4-11.5 microns range has
been determined from transmittance spectra through reverse synthesis. From this analysis, the most suitable evaporation
conditions for ZnS thin films deposition have been defined in terms of film properties and intended applications on
thermal IR multilayer coatings.
Afterwards, adhesion properties of ZnS films deposited under the optimised conditions have been analysed. ZnS
films deposited at 120°C and 4 nm/s peeled off when subjected to MIL-F-48616 standard surface durability testing. The
use of a MgO bonding layer to enhance the ZnS film adherence to the substrate has been proposed and its effect on the
ZnS film properties has been studied. Finally, the mechanical stability of the ZnS coating under MIL-F-48616 standard
testing has been confirmed for films grown onto MgO coated substrates.