Confotec® MR520 – 3D scanning laser Raman microscope-spectrometer

Interdisciplinary research at the sub-micrometer range:

  • Confocal Raman microscopy / fluorescence microscopy
  • Compact modular system
  • Wide spectral range (UV – ultraviolet, VIS – visible, IR – infrared)

  • High sensitivity

  • High temporal and thermal stability

As diamond is a very hard material, diamond coating is widely used in cutting or polishing tools. To improve performance of diamond coating tools, analysis techniques capable of test samples with high spatial resolution are required. Raman/photoluminescence spectroscopy is a good candidate for such measurements due to ultra-high sensitivity to the structural perfection of diamond.

Raman spectrum of a stress free diamond microcrystal contains a sharp peak at 1332 cm-1 (Fg.1a). The full width at half maximum (FWHM) of this peak is ~1.7 cm-1. Any deviation from the “perfect” parameters may be indicative of the presence of strain in diamond. Complimentary to the Raman spectroscopy, the broadband photoluminescence peak (Fig.1b) is associated with color NV centers. The intensity of peak shows defects concentration in diamond crystals.

This application note devotes to characterization of diamond coating tools by confocal Raman and photoluminescence techniques using Confotec® MR520 microscope (SOL instruments).

The investigated tool contains diamond grains fixed on the functional part via a bonding material. Approximate micron range of diamond micro-crystals is 15 – 25 µm Raman and NV photoluminescence images of tool (150×150 µm) are shown in Fig.2. It is possible to see from the experimental data, there is homogeneous distribution of diamond grains along the working surface of a tool (Fig.2a). From analysis of the intensity of NV photoluminescence peak (Fig.2b) we can conclude that diamond crystals have got varied contents of defects. Some of crystals include a small amount of defects. Such crystals are marked with the white circles in Fig.2.

One more detailed measurement of the tool (70×70 µm area) is shown in Fig.3. Measurement result on this area is similar to the previous one: distribution of diamond grains along the working surface is uniform (Fig.3a,b), and concentration of defects in diamond micro-crystals is significant (Fig.3d). The position of diamond line (Fig.3c) illuminates the strain distribution in different grains. Red color on the stress map (Fig.3c) represents regions with compressive stress. Micro-crystals with the increased stress are marked in Fig.3 with dash-dot circles.

Summary: We have demonstrated that Confotec® MR520 (Raman, photoluminescence techniques) can be used to check diamond coated tools.

Publication date: 2 December 2013

Raman spectra of synthetic diamonds
Fig.1. Raman spectra of synthetic diamonds with grain size of 20 (a) and 70 microns (b) approximately. The Raman spectra were recorded with 532 nm excitation. Broadband photoluminescence feature on the last picture is associated with defects in diamond.
Characterization of diamond coated tool
Fig.2. Characterization of diamond coated tool: (a) Raman intensity image at 1332 1/cm and (b) photoluminescence image. Scan size is 150×150 µm.
Characterization of diamond coated tool
Fig.3. Characterization of diamond coated tool: (a) optical image (70×70 µm); (b) Raman intensity image at 1332 1/cm; (c) Diamond line position; (d) photoluminescence image.

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