Molecular Dynamics Investigations of Energetic Cluster Bombardment of Metal-organic Interfaces and Organic Solids
Open Access
- Author:
- Kennedy, Paul Earl
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- January 18, 2013
- Committee Members:
- Barbara Jane Garrison, Committee Chair/Co-Chair
Lasse Jensen, Committee Member
Adrianus C Van Duin, Committee Member
Nicholas Winograd, Committee Member
Barbara Jane Garrison, Dissertation Advisor/Co-Advisor - Keywords:
- molecular dynamics simulations
MD
cluster bombardment
C60
secondary ion mass spectrometry
SIMS - Abstract:
- The objectives of this dissertation are two-fold and are related by the underlying theme of utilizing molecular dynamics simulations to investigate the different types of damage inflicted on substrate materials by the impacts of energetic clusters. Accumulation of such damage can lead to unsuccessful secondary ion mass spectrometry depth profiling experiments. The first objective is to develop and test a methodology for incorporating reactions in cluster bombardment simulations, which has been shown to be difficult due to the high computational cost of such simulations. Initially, a reactive force field used to describe the interactions between atoms was tested for its ability to model reactions related to the build-up and removal of damage during depth profiling experiments of two organic polymers. Next, a protocol for a mixed resolution model was designed that partitioned a test sample of solid benzene into atomistic and coarse-grained regions. The atomistic region incorporated interactions described by a complex reactive potential, and the coarse-grained region’s interactions were described by simple two-body potentials. Test simulations showed that the dynamics of cluster bombardment transferred smoothly between the regions of the mixed resolution system. Finally, as a proof of principle, the molecular benzene system was used in simulations of energetic C60, Ar18 and Ar60 cluster bombardments to analyze the overall differences in sputtering yields and damage formation. The results from the C60 bombardment were also used in an investigation that successfully determined the relationship between C60 and Ar in cobombardment experiments. The second objective of this dissertation is to elucidate through MD simulations the difficulties in SIMS depth profiling experiments of metal-organic interfaces. By performing C60 bombardment simulations on systems composed of varying metal overlayer thicknesses on an organic substrate, the dynamics related to the early ejection of substrate molecules along with the implantation of metal clusters in the substrate were uncovered. Results from these simulations provide a clear picture of the dynamics occurring in the SIMS depth profiling experiments. The work presented in this dissertation is beneficial to the theoretical and experimental advancement of the SIMS field. The mixed resolution model has shown that both a reactive atomistic and coarse-grained description of a system can be used together in cluster bombardment simulations to greatly reduce their computational cost, which will enable its use in simulations to elucidate the chemical effects of cluster bombardment. For SIMS experimentalists, the simulations of the cluster bombardment of metal-organic interfaces have presented a microscopic view of the dynamics occurring during the bombardment process. A microscopic view that reveals the problems that must be overcome to successfully analyze materials that incorporate metal-organic interfaces with the SIMS technique.