Materials Characterization

Glow-discharge optical emission spectroscopy

Glow Discharge Optical Emission Spectroscopy (GDOES) is a widely used analytical method for the determination of elemental compositions for both, metallic and non-metallic materials. Furthermore, the elemental concentration as a function of the depth of coatings with thicknesses up to several micrometers can be realized. Therefore, a uniform material removal is achieved on the sample surface by means of a glow discharge and the light emitted by the sputtered atoms is measured in the spectrometer. With an adequate calibration, the intensity of the emitted light can be recalculated into the elemental composition of the sample. While the lateral resolution is determined by the anode diameter, which is 4mm as standard, depth resolutions with values below 10nm can be achieved.

 

Technical data:

  • Detectable elements: all
  • Lateral resolution: ≥2mm
  • Depth resolution: ≥10nm
  • Detection limit: ppb
  • Sputtering rate: 1-10µm/min
  • Depth profile: yes, up to ~100µm

3D Confocal Laser Scanning Microscope

The microscope is used for the characterisation of surface by recording and analysing 3 dimensional surface topographies. The laser beam scans the surface in x and y direction while a stepwise change of the focus point is achieved via the objective. The microscope is applied to analyse surface subjected to mechanical loading, e.g. after tribological tests, to measure 3 dimensional structure in microelectronics and nanoelectronics, to measure the thickness of opaque and transparent films as well as to determine the surface roughness.

 

Technical data:

  • Device: Keyence VK-X1100
  • Laser Wavelength: 404 nm
  • Objectives: 5x, 10x, 20x, 50x and 150x
  • Sample Stage: 100 mm x 100 mm

X-ray Diffractometer

X-ray diffractometry is used for the determination of the crystallographic structure of thin films, powders and bulk materials. At the department, two diffractometers of type Bruker AXS D8 Advance are available. These diffractometers consist of a source of radiation (copper X-ray tubes), monochromators, various slits and detectors. During the measurement the sample is irradiated with monochromatic X-rays and the diffraction at the crystal lattice is investigated. By scanning a pre-defined range of diffraction angles maxima in the reflected X-ray intensity can be determined being characteristic for each crystalline material. This consequently enables the determination of the phase composition of solid samples. The detectors available at the department are energy-dispersive, which results in an excellent signal-to-noise ratio, especially for steel samples, which tend to fluoresce under copper radiation. A Eulerian cradle allows to tilt the investigated sample thus making stress and texture analyses feasible. A high-temperature chamber (Anton Paar 1200 N) provides the possibility to heat samples up to 1200 °C in vacuum, air and oxidizing atmospheres enabling the investigation of phase transformations and chemical reactions.

 

Technical data:

  • Measurement geometry: Bragg-Brentano, parallel beam, gracing incidence, transmission, reflection
  • Radiation: copper K-alpha, line and point focus
  • Detectors: scintillation counter, energy dispersive detectors (0D and 1D mode)
  • Sample holder: nine position sample changer, Eulerian cradle, capillary holder and high-temperature chamber (up to 1200 °C)
  • Investigation atmospheres: vacuum, air and oxidative
  • Software: ICDD pdf-database 2018 und EVA (phase analysis), TOPAS (quantitative determination of phase compositions, Rietveld), TEXTURE (texture determination), LEPTOS (calculation of residual stresses)

Biaxial Stress Temperature Measurement

The biaxial stress-temperature measuring system “Mutti 2000” is a self-constructed facility to measure the temperature dependency of stresses in thin films. Using two parallel laser beams, the curvature resulting from the stresses of a substrate coated on one side can be measured and the stresses can be calculated. The sample is positioned in a high-vacuum chamber, enabling to investigate stress relaxation mechanisms in-situ during a thermal cycle up to 700°C. In addition to stresses and stress relaxation effects, the thermal expansion coefficient of the film can be determined from the thermal cycle.

 

Technical data:

  • Measurement principle: cantilever beam method
  • Substrate size: 20 x 7 x 0,3 mm (preferably silicon)
  • Laser: Melles-Griot 3222 H-PC
  • Turbomolecular-pumped vacuum chamber with radiation heaters
  • Minimum pressure: 5x10-7 mbar
  • Temperature: 25 - 700°C
  • Heating rate: 1-20°C/min