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Materials Analysis with Raman Spectroscopy
Typical applications of Raman spectroscopy include contamination identification, chemical phase characterization and compositional analysis. Comparing the unique spectrum of an unknown material to a spectral database enables identification of unknown contaminants. Spectra from several common polymers used in semiconductor device packaging are shown in Figure 1.
Fig 1. Raman spectra of common organic polymers.
Using Raman spectroscopy, Cerium Labs analyzed raw materials used to manufacture Solid Oxide Fuel Cells to verify their crystalline phase. Figure 2 shows a spectrum of yttria-stabilized zirconia (YSZ) that is a mixture of tetragonal and cubic phases. Metal silicides used in microelectronics fabrication show conversion from metal rich to silicon rich phases. Each of these phases has a distinct Raman spectrum that is used to monitor the conversion process.
Fig 2. Raman spectrum of YSZ showing a mixture of the tetragonal and cubic phases.
Raman spectroscopy is also used to determine the purity of single-walled (SW) and multi-walled (MW) carbon nanotubes. Figure 3 shows a spectrum of a SW carbon nanotube sample. Purity of the nanotubes in solution is determined by the presence or absence of the carbon D band at 1350 cm-1.
Fig 3. Raman spectrum of single walled carbon nanotubes.
Raman Spectroscopy is an inelastic light scattering technique that measures the vibrational spectra of molecules. Cerium Labs operates a Renishaw Micro-Raman Spectrometer with multiple excitation wavelengths (488 nm, 514 nm and 785 nm) giving us the ability to analyze organic and inorganic materials. Additionally, the spatial resolution of the Raman microscope is approximately 1 micron, allowing analysis of microscopic features that are too small for analysis by other methods such as FTIR. |