Angle Resolved X-Ray Photoelectron Spectroscopy (AR-XPS)

  • non-destructive depth profile analysis of surfaces by measuring XPS data at surfaces of solid materials when changing the angle between analyzer acceptance axis and sample surface
  • indirect depth profile information due to the change of the effective information depth changes with the angle - key parameter are the effective attenuation length (EAL) of the electrons used
  • for quantification model calculation are inevitable, surface models have to be assumed, information content is limited
  • additional limitations: EALs of the (unknown) surface layers have to be assumed, elastic scattering at high measuring angles, roughness influences
  • experimentally sequential data acquisition with sample tilt or parallel detection with 2-dimensional detectors and special analyzer modes
  • depth region 2 ... 10 nm depending on electron energy

 

Analytical features:

  • (automatic) non-destructive angle dependent measurements (ARXPS)
  • assumptions for the surface near structures from the measures spectra and from a priori information of the samples necessary
  • look for the appropriate material parameters (density, EAL, ...)
  • model calculations and optimization of the model solution with the measured intensities

Examples

Non-destructive depth analysis using angle-resolved measurements (ARXPS) at a model oxide layer for thin tunnel barriers.

Comparison of measuring values (points left) and results of calculations (lines left) for an assumed surface structure (right).

For the simulation of the oxide layer beside O two different peak area portions for Al were used (oxide -metal).