Surface characterization of nickel alloy plasma-treated by O_2/CF_4 mixture

摘要

The micro-or nano-structured mold used for polymer embossing typically must be coated with an anti-adhesion material to reduce its interation with the embossing.The mold is typically made by nickel sulphamate electroforming.For the anti-adhesion coating to adhere to the mold,the nickel mold surface must be clean and preferably unoxidized or possess reactive groups sutable for covalent bonding with the anti-adhesion coating.The effectiveness f plasma cleaning using mixtures of oxygen (O_2) and tetrafluoromethane (CF_4) with varying ratios versus liquid-only cleaning was investigated.To simulate the nickel mold,Ni200 alloy was used.Plasma treatment using mixtures of O_2 and CF_4 was found to be more effective in cleaning the Ni200 surface than liquid only cleaning or pure O_2 or pure CF_4 plasma treatment.Using a 1:1 O_2/CF_4 mixture plasma,the contact angles of water,glycerol and diiodomethane on Ni200 were the lowest and the calculated surface energy was the highest among the investifgated treatemnts.From X-ray photoelectron spectroscopy (XPS),the amount of organic contamnation on Ni200 was significantly reduced with plasma treatment.For liquid-only cleaned samples,metali nickel,NiO and Ni(OH)_2 are present on the surface.With pure O_2 or pure CF_4 or 1:1 O_2/CF_4 mixture plasma,both oxidation and fluorination occur and the surface contains combinations of NiF_2,Ni(OH)_2,Ni(OH)F,Ni_2O_3 and NiO_1.5F instead (without metallic nickel and NiO).The proportions of these different compounds vary according to the O_2/CF_4 ratio;O/Nir ratio is highest for pure O_2 plasma treatment,whilst F/Ni is higherst for pure CF_4 plasma treatment.