/
Surface Analysis Techniques XPS AES SIMS
Save to my account
Sign up
Surface Analysis Techniques XPS AES SIMS
Lecture 8
Study
1
Question
What is the formula for calculating the binding energy (E_B) in X-ray Photoelectron Spectroscopy (XPS)?
Answer
E_K is the measured kinetic energy of the emitted photoelectron
2
Question
In surface chemical analysis, What surface region is ideal for surface chemical analysis? Based on binding energy what info does this provide?
Answer
Electrons emitted from the near-surface region of 5-10 nm provide valuable information about the surface's elemental composition and chemical state
3
Question
How does Auger Electron Spectroscopy (AES) differ from X-ray Photoelectron Spectroscopy (XPS) in terms of electron emission?
Answer
In AES, an electron from a higher energy level fills a core hole and the energy released ejects another electron (Auger electron), which generally has very low kinetic energy. In XPS, incident photons directly eject an electron from a core level as a photoelectron.
4
Question
Different modes in the AE spectrum
Answer
5
Question
XP Spectrum, Chemical Shifts and Spatial Maps
Answer
• Elemental analysis are possible and spatial maps can be produced. Spatial resolution of XPS maps is however poorer than AES, but quantitative analysis is relatively better due to lesser (and more quantifiable) matrix effects. • Chemical shifts in binding energy peaks can help identify the local environment like bond state of C. Depth profiling is also possible (similar to AES).
6
Question
What fundamental principle allows Secondary Ion Mass Spectroscopy (SIMS) to distinguish ions and determine their composition?
Answer
SIMS relies on measuring the mass-to-charge ratio (m/z) of secondary ions ejected from a surface after being bombarded by primary ions, using their transit time through a magnetic or electric field to separate ions based on mass and charge.
7
Question
Formula for time of flight (t) of ions in SIMS
Answer
time of flight (t) of ions through a flight path L under an accelerating voltage V to their mass-to-charge ratio (m/z)
8
Question
Why is controlling the various ions produced in SIMS more complex compared to XPS or AES?
Answer
SIMS produces a wide variety of secondary ions with different masses and charges, often including molecular fragments, making it very difficult or impossible to control or predict which ions are emitted, complicating interpretation and requiring sophisticated analysis.
9
Question
Which element can SIMS detect effectively that XPS and AES typically cannot, and why?
Answer
SIMS can detect hydrogen (H), which is difficult for AES and XPS to detect because these methods depend on electron emission that hydrogen, being a very light element with no core electrons, does not produce effectively.
