The Static Limit in MeV Secondary Ion Mass Spectrometry

Area of Science:

• Surface Science
• Mass Spectrometry
• Materials Analysis

Background:

• The static limit in Secondary Ion Mass Spectrometry (SIMS) defines the threshold beam fluence for analyzing virgin surfaces.
• Common SIMS techniques operate below a threshold of approximately 10^12 ions/cm^2.
• MeV-SIMS utilizes MeV energy primary ions, relying on electronic excitations for secondary ion desorption.

Purpose of the Study:

• To investigate the applicability of the static limit in MeV-SIMS.
• To understand the energy dependence of disappearance cross-sections for organic targets in MeV-SIMS.
• To analyze the dynamics of secondary ion mass spectra during prolonged MeV-SIMS bombardment.

Main Methods:

• Measurement of disappearance cross-sections for organic targets using MeV-SIMS.
• Bombardment of targets with chlorine primary ions at three different MeV energy levels.
• Monitoring of secondary ion yields over time to study spectral dynamics.

Main Results:

• The static SIMS regime is generally applicable within similar fluence ranges for MeV-SIMS as for common SIMS.
• Disappearance cross-sections exhibit a dependence on primary ion beam energy, with unexpected characteristics below 10 MeV.
• Secondary ion yields and fragmentation patterns were monitored during prolonged bombardment, aiding in molecular identification.

Conclusions:

• MeV-SIMS can be operated within the static SIMS regime, enabling surface-sensitive analysis.
• The energy dependence of disappearance cross-sections requires careful consideration, especially at lower MeV energies.
• Analysis of secondary ion dynamics provides valuable insights into molecular fragmentation and identification in MeV-SIMS.