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.

Date Published: 25 September 2008
PDF: 9 pages
Proc. SPIE 7101, Advances in Optical Thin Films III, 71011K (25 September 2008); doi: 10.1117/12.797413

Published in SPIE Proceedings Vol. 7101:
Advances in Optical Thin Films III
Norbert Kaiser; Michel Lequime; H. Angus Macleod, Editor(s)