We want to make gold film(40nm) on the BK7 using the adhesive material Cr(2nm). Here's my work order. First, we evaporate the Chromium on the glass(BK7) by thermal evaporator with 0.2 A/sec.(when we scrach the film, it does not damaged) Second, the champer places in the room temperature for 2 hours to cool the internal chamber and then vent the chamber. Third, change the tungsten boat with different material to evaporate Gold (material changed Cr to Gold) (we have only one evaporating channel) Finally, evaporate the gold on the Cr evaporated BK7 glass with 0.4 A/sec. condition; room temperature 20 celcius, 2*10^(-6) torr. Cr; 99.95 %, Au; 99.99 %. And I wonder why the gold film is so easily peeled off from Cr film just rubbing with fingers. (adhesion is too bad)
To make it strong enough for rubbing you may need thicker films, both Cr layer and Au layer. And also the evaporating rate seems slow to me. Try 3~5 A/sec, or faster. I'm not sure...That may depend on your equipment.
And I think it'll be better if you do it continuously, like don't expose it to the air after deposit Cr layer and before Au layer.
Hope it'll help~good luck!
I guess gold does not adhere very well onto chromium oxide.
any plasma possible to clean/sputter the chromium oxide surface?
I have a lot of experience with Cr-Au adhesion and Johan is absolutely right. Cr films oxides very easily is air so Au will not stick well. An O2 plasma clean should help but you must do the deposit immediately after the cleaning and it still may not be great adhesion. The best solution is not break vaccuum between the Cr adhesion layer and the Au.
I have had exactly the same issue, if you break the vaccuum between the two evaporations the Au will not stick. Since you don´t have two evaporation sources, your best solution would be to use a different adhesion layer, perhaps titanium or ITO.
As Stamatis and Brian advised, best not to open chamber between evaporations. Also is this an oil diffusion pumped system? If oil is around, and you are pumping for a while, backstreaming oil can condense on the substrate and destroy the adhesion easily.
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