I have been tasked with running protective gold coatings using EBEAM deposition. My understanding is that a THIN (10nm) layer of ZnS over the Cr/Au coating (on diamond turned Al Mirrors for spectroscopy) will suffice... will I lose %reflectivity? Is there a SOP for this coating?
Using Temescal BJD -1800 system.
ZnS? SiO? How thick? Do not want to introduce any strange bands or increase throughput. Anyone with any HR Protected gold thoughts also encouraged to reply!!
Well, If I understand your thin film layers stock, it looks Al/Cr/Au/ZnS, here the Cr layer is being Introduced to enhance the adhesion b/w Al and Au, and now you would want to protect the Au from environmental degradation and /or self tarnishing, without compromising the Initial reflectivity i.e Al/Cr/Au system. Since, you have not mentioned about your reflectivity measurement equipment whether that measures total or specular reflectivity. Nevertheless, the drop in reflectivity basically depends on (a) thickness, and (b)Refractive Index of ZnS relative to preceding thin film. I think 10nm is too less, people use 100-200nm if I am not wrong!!. Let’s wait and hear from our RG friends comments/feedback
Thanks! We see right now about 98% reflectivity. With HR Gold we intend to produce 99.8& with exponential loss per bounce. Yes the Cr is used as an interlayer between the Au and Aluminum substrate. Approx. 200nm Au will be deposited over 30nm Cr in ebeam evaporation chamber. I have many materials available at my disposal (Al2O3, SiO, SiO2, ZnS, MgF2 etc...) I guess I am wondering if there is a standard practice when it comes to protective gold surfaces when maintaining maximum reflection of the gold is of much importance.
A halfwave of either ZnS or SiO2 at 633nm is industry standard for protective gold coating. It will be protected and will give good environmental durability, yet it can still be scratched if to much pressure is applied to coated surface.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Inorganic Materials
- Metals
- Alloys
- Steel