Molecular Dynamics Simulations of Particle Bombardment Induced Desorption Processes:  Alkanethiolates on Au(111)

Molecular dynamics has been used to model Ar atom induced sputtering of n-alkanethiolate molecules self-assembled on Au(111). The aim is to discover possible mechanisms of formation of the various sputtered species such that their relationship to surface chemistry can be understood. To model the system, a blend of pairwise and many-body potentials are used to represent the interatomic interactions. To simulate the formation of gold−thiolate clusters required the development of the potential for the Au−S interaction. The resulting model predicted a “mass spectrum” of atomic and cluster species which is remarkably similar to the experimental static SIMS spectra of n-alkanethiolate SAMs on gold. A number of emission mechanisms for the production of hydrocarbon fragments and gold−thiolate clusters are suggested by the model which provide very valuable insights into the relationship between the spectral features and surface chemistry.