Selective Penetration of Metal Atoms — New Evidence and Application for the Simple Ideal Penetration Model of the Long-Chain Close-Packed Alkanethiol Self-Assembled Monolayers on Au(111)

In the study of the vapor deposition of metal atoms onto long-chain alkanethiol self-assembled monolayers (CnSH-SAMs, n>10) on Au(111) substrate, metal atoms with different diameters can penetrate selectively into the CnSH-SAMs or not, which looks like the “size exclusion effect”. In this paper, we proposed a new mechanism for the metal atoms penetration by establishing a simple ideal penetration model of the long-chain CnSH-SAMs with defect-free structure on Au(111). The intrinsic and regular–distributed channels with ∼ 3 Å diameters (which are decided by the framework size of the three-aggregate of the CnSH molecules) were deduced. This new penetration mechanism can explain reasonably the selective penetration of metal atoms into the long-chain CnSH-SAMs on Au(111): When the driving force is applied, the metal atoms with diameter smaller than 3 Å will overcome the van der Waals interaction among the neighboring hydrocarbon chains and penetrate into the CnSH-SAMs through the ∼ 3 Å channels reaching to the surface of Au(111), while the metal atoms with large diameter (> 3 Å) can not penetrate.