Surface Analysis


Research interests

Our main research interests are focused on the element and binding state analysis at solid surfaces with methods of electron spectroscopy, which can characterize materials on a nanometer depth scale. The spectroscopic methods we use are

In combination with ion sputtering we also make depth-profiling with these methods typically in a depth range up to 1 µm; with angle-resolved XPS (ARXPS) also non-destructive in the depth-range of some nm.
We investigate mainly materials for Li-ion batteries and valence states at specific oxides, but also thin film systems and properties of (modified) surfaces. Bulk materials, such as metallic glasses, are also in the focus of interest. See below for some examples.

Methods applied in our group

We use our state-of-the-art surface analytical equipment for the characterization of:

Surface analysis

  • binding state analysis especially with XPS due to peak changes
  • in situ preparation (see below) to avoid surface changes from atmosphere
  • local element analysis with AES down to approx. lateral dimension of 100 nm, with XPS 100 µm
  • data analysis (factor analysis) for both AES and XPS for semi-automatic binding state analysis
  • also for non-conducting material (XPS)

Depth profile analysis

  • sputter depth-profiling using AES (variable area regions 1*1 µm to 100*100 µm, typ. 10 nm/min sputtering rates) and XPS (region typ. 0.5 mm, typ. 1.. 3 nm/min sputtering rate)
  • sample rotation for minimization of influences from roughness
  • non-destructive depth-profile analysis with ARXPS in the range up to approx. 5 nm
  • also for non-conducting material (XPS)

In situ preparation

  • "quasi in situ" preparation using transfer boxes between glove-box and XPS/AES instruments using Ar as transport gas - no contact to air
  • sputter cleaning - standard method for removal of surface contamination, changes of the material by the ion impact possible!
  • heating (resistive and with e-beam) - phase formation, segregation
  • fracturing and scraping - bulk and grain boundary investigation, cleaning without ion bombardment
  • film deposition (evaporation, magnetron sputtering) - interface phase formation and film growth modes

Current research projects, current results:

  • study of chemical changes in materials for Li-ion batteries, both anode and cathode material
  • basic properties of complex transition metal oxides
  • growth of thin diffusion barrier material (Ta, Ti, W, and its nitrides) with XPS including ARXPS
  • simulation of roughness influences in ARXPS
  • bonding states and impurities at C-nanomaterials

Equipment