Monolayers of 11 - trichlorosilylundecyl thioacetate : A system that promotes adhesion between silicon dioxide and evaporated gold

This art ic le descr ibes the use of sul fur-containing organic monolayers to improve the adhesion of gold to sil icon substrates having a native sil icon dioxide surface layer. Gold adheres to clean sil icon,r but not to sil icon dioxide.2 The affinity of gold toward sil icon dioxide can be improved by coating with chromium3 or titaniumt films or by adding interlayers containing fluoride salts.a Bombardment of gold-covered si l icon dioxide with electronss or heavy ions67 also enhances adhesion. Thin (< 100 A) .ovalent ly-bonded alkyls i loxane f i lms containing ani ines or epoxides improve the adherence of -eold to glass. t Go ld sur l 'aces have a h igh a f t ' i n i t r fo r a lk r l th io ls ( R S H ) . ' " ' d i a l k v l s u l f i d e s ( R . S ) . " ' r a n d c l i a l k r l c i i s u l f i d e s ( R S S R ) . ' t T h e m e c h a n i s * t L f b o n d i n g b e n r e e n o r g a n r e sulfur compounds and gold have not been clearly established, although surface gold thiolates have been suggested as important.rs'ra Allara and Nuzzo have exploited the affinity of gold for sulfur by using a relatively thick organic polysiloxane layer containing a disulfide to improve the adhesion of gold to alumina and sil icon dioxide.15'16 We have shown previously that monolayers can be used to promote adhesion.'t Here we demonstrate that covering a Si/SiO, substrate with a covalently attached organic monolayer film containing thiol groups (and possibly disulfides derived from them) or thioacetate groups improves the adhesion of gold to the substrate.