Molecular Depth Profiling and Chemical Imaging with Cluster ToF-SIMS
Open Access
- Author:
- Shen, Kan
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- July 10, 2015
- Committee Members:
- Nicholas Winograd, Dissertation Advisor/Co-Advisor
Nicholas Winograd, Committee Chair/Co-Chair
Barbara Jane Garrison, Committee Member
Christine Dolan Keating, Committee Member
Yingwei Mao, Committee Member - Keywords:
- ToF-SIMS
molecular depth profiling
chemical imaging - Abstract:
- The work presented in this dissertation is concentrated on improving the fundamental understanding of molecular depth profiling and chemical imaging associated with time-of-flight secondary ion mass spectrometry (ToF-SIMS) equipped with cluster ion sources, mainly C60 and argon gas cluster ion beams (Ar-GCIBs). A gold-cholesterol hybrid system is used to elucidate the reasons for the difficulties of depth profiling of heterogeneous thin film structures. The model study provides mechanistic insight into depth profiling of hybrid materials and offers an appropriate strategy for improving the quality of the depth profiles. Depth profiling of trehalose thin films is investigated under different Ar-GCIBs bombardment conditions to elucidate the influence of cluster size and kinetic energy on the formation of molecular ions. The study provides insight into selecting optimal Ar-GCIBs characteristics for molecular depth profiling of organic materials. Finally, room temperature ionic liquids (ILs) are employed in mass spectrometry imaging experiments. The surface and the internal structure of microspheres synthesized in ILs are investigated by the high spatial resolution imaging and depth profiling capabilities of cluster ToF-SIMS. The study introduces a new type of matrix for imaging mass spectrometry and provides insight into the key drivers and restraints behind ToF-SIMS three-dimensional (3D) molecular analysis. Overall, the thesis work is of great value for the fundamental understanding cluster ion-solid interactions in ToF-SIMS analysis and is beneficial for the advancement of the technique.