I suppose annealing in atmosphere with high pressure of sulfur vapor. It should be noted that temperature of your film must be above of 150 C for prevent condensation of sulfur on the surface.

Thank you Alexander sir.

Can you use H2S at appropriate pressure and temperature?  See: http://www.scientific.net/AMR.818.3

Dear colleague

Although my field is theoretical physics , but you can use vacuum process , this was used by many researcher so non-vacuum conditon.

Regards 

No, Mr. Alan. I am not using H2S pressure