Preparation and Properties for Germanium Carbide Double-Layer Films Used as Antireflection and Protection Coatings

Germanium carbide (Ge1-xCx) films have numerous attractive properties,such as low stress and light absorption,good adhesion on many infrared substrates such as ZnS and Ge.In particular,their refractive index can be widely varied with composition within the range of 2～4.These excellent performances make Ge1-xCx films promising candidates for applications in the field of multilayer antireflection and protection coating of IR window.Up to the present,some optical,electrical,and structural properties have already been reported for Ge1-xCx films prepared by different deposition techniques.However,as regard the application of the Ge1-xCx films for antireflection and protection coating of the IR ZnS window,the desired IR transmission performance has not been achieved,though the mechanical pro-perties of ZnS substrates overcoated by these durable Ge1-xCx coatings have been significantly improved.In this work,an antireflective Ge1-xCx double-layer coating,deposited on ZnS substrate via magnetron sputtering,has been developed.It is found that this Ge1-xCx double-layer coating can significantly enhance the infrared transmittance in the interesting band of 8～12 μm and hardness of ZnS substrate,and it exhibits the excellent thermal stability and heat shock resistance.These results suggest that such a double-layer Ge1-xCx can be used as an effective antireflection and protection coating for ZnS infrared window.