Alternative method for the representation of microstructures in polycrystalline materials

Composite Raman intensity-distribution map on a polycrystalline CuInSe<sub>2</sub> thin film.

Composite Raman intensity-distribution map on a polycrystalline CuInSe2 thin film. © HZB

EBSD orientation-distribution map from the same identical specimen position. </p>

EBSD orientation-distribution map from the same identical specimen position.


Also Raman microspectroscopy in an optical microscope provides the means to determine local crystal orientations of polycrystalline materials over large sample areas. This method can be used alternatively to electron backscatter diffraction in a scanning electron microscope. It was shown by a team from Helmholtz-Zentrum Berlin and the Federal Institute for Materials Research and Testing (BAM) that both characterization techniques result in similar orientation distribution maps on areas of several hundreds of square micrometers.

Most solid materials are of polycrystalline nature. In which way the individual grains are oriented in the material can be relevant for its functional properties. In order to determine the corresponding orientation distributions on large specimen areas, generally, a scanning electron microscope is employed. The specimen surface needs to be prepared, before it can be probed under vacuum by an electron beam and analyzed using electron backscatter diffraction (EBSD).

It has now been shown by a team at HZB headed by Dr. Daniel Abou-Ras, together with Dr. Thomas Schmid from BAM, that equivalent orientation distribution maps can be obtained also by means of Raman microspectroscopy. This method needs only an optical microscopy setup, no time-consuming specimen preparation, and can also be conducted under ambient conditions.     

The scientists used CuInSe2 thin films as a model system for their study. They showed that the experimental Raman intensities correspond well with the theoretical intensities calculated by using the local orientations from the EBSD map. “The sample area was scanned by a laser beam using step sizes of 200 nanometers. For such measurement conditions, the sample environment needs to be controlled carefully and kept stable for several hours,” explains Dr. Abou-Ras.

The application of Raman microspectroscopy for orientation distribution analysis is possible in principle for all polycrystalline materials, whether they are inorganic or organic, as long as they are Raman active.

The report has been published in Scientific Reports:
Orientation-distribution mapping of polycrystalline materials by Raman microspectroscopy, Norbert Schäfer, Sergiu Levcenco, Daniel Abou-Ras,Thomas Schmid, Doi: 10.1038/srep18410


You might also be interested in

  • Watching indium phosphide at work
    Science Highlight
    Watching indium phosphide at work
    Indium phosphide is a versatile semiconductor. The material can be used for solar cells, for hydrogen production and even for quantum computers – and with record-breaking efficiency. However, little research has been conducted into what happens on its surface. Researchers have now closed this gap and used ultra-fast lasers to scrutinise the dynamics of the electrons in the material.
  • Freeze casting - a guide to creating hierarchically structured materials
    Science Highlight
    Freeze casting - a guide to creating hierarchically structured materials
    Freeze casting is an elegant, cost-effective manufacturing technique to produce highly porous materials with custom-designed hierarchical architectures, well-defined pore orientation, and multifunctional surface structures. Freeze-cast materials are suitable for many applications, from biomedicine to environmental engineering and energy technologies. An article in "Nature Reviews Methods Primer" now provides a guide to freeze-casting methods that includes an overview on current and future applications and highlights characterization techniques with a focus on X-ray tomoscopy.
  • IRIS beamline at BESSY II extended with nanomicroscopy
    Science Highlight
    IRIS beamline at BESSY II extended with nanomicroscopy
    The IRIS infrared beamline at the BESSY II storage ring now offers a fourth option for characterising materials, cells and even molecules on different length scales. The team has extended the IRIS beamline with an end station for nanospectroscopy and nanoimaging that enables spatial resolutions down to below 30 nanometres. The instrument is also available to external user groups.