| AVS 66th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology Division | Wednesday Sessions |
| Session NS+2D+AS-WeA |
| Session: | Probing and Modifying Surface and Interfacial Chemistry at the Nanoscale |
| Presenter: | Da-Jiang Liu, Ames Laboratory and Iowa State University |
| Authors: | J. Lee, Ames Laboratory and Iowa State University J.W. Evans, Ames Laboratory and Iowa State University T.L. Windus, Ames Laboratory and Iowa State University P.A. Thiel, Ames Laboratory and Iowa State University D.-J. Liu, Ames Laboratory and Iowa State University |
| Correspondent: | Click to Email |
Stabilities of metal-ligand complexes on surfaces are crucial for the process of self assembly of 2D structures. We provide a comprehensive theoretical assessment at the level of Density Functional Theory (DFT) of the stability of various coinage metal-sulfur complexes, MmSn, with M=Cu, Ag, and Au, both in the gas-phase and also for these complexes adsorbed on the (111) and (100) surfaces of the same coinage metal. An early influential theoretical study on S/Cu(111) proposed that the Cu3S3 complex being the most stable copper containing species. Later combined low temperature STM and DFT studies suggest that a heart-shaped Cu2S3 and its concatenations being more stable. Larger and even more complex Ag-S complexes have being observed for S/Ag(111). No complexation have been observed for S/Cu(100) and S/Ag(100). On the other hand, a Au4S5 complex and its fragmentations have being observed for S/Au(100), but no complexation is observed for S/Au(111) at low S coverage. We select a set of nine types of complexes, chosen for their proposed existences, intrinsic stabilities, and affinities for adsorption on metal surfaces. For the adsorbed species, we calculate various aspects of their energetics including their formation energy from sulfur adsorbed on terraces and from metal atoms that are in thermal equilibrium with the substrate. From this perspective, our DFT analysis shows that Ag2S3, Ag3S3 and many larger complexes on Ag(111) are strongly stable, Cu2S3 is stable and some larger complexes are marginally stable on Cu(111), but only Au4S4 on Au(111) is stable. In contrast, no complex is stable on Cu(100) and Ag(100), but a group of complex is stable on Au(100), with Au4S5. DFT results are consistent with experiments with the apparent exception of Au(111). This comprehensive assessment of energetics provides key input for statistical mechanical analysis of S adlayer ordering in the absence of complexation, and of the kinetics of complex formation and associated enhanced mass transport and surface dynamics.