Integrated Raman and electron microscopy: correlative chemical specificity and nanoscale resolution

Frank Jan Timmermans

Research output: ThesisPhD Thesis - Research UT, graduation UT

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This thesis describes the integration of a Raman microscope in a focused ion beam - scanning electron microscope (FIB-SEM). Raman micro-spectroscopy enables chemical specific characterization, while electron microscopy enables high resolution imaging. The Raman - SEM combination thus enables the correlation of chemical specific micro-spectroscopy with nanometer resolution morphological imaging. FIB materials ablation adds to this a micromachining capability. The Raman - FIB combination enables spectroscopic analysis of FIB treated samples. Conversely FIB ablation of surface material can be used to reveal deeper layers in a specimen for subsequent Raman analysis. The integration into a single system facilitates fast sequential analysis and treatment on any single location on the sample.

Capabilities of the integrated microscope are demonstrated on a wide variety of sample materials. Chemical specific identification of micron sized materials, combined with SEM analysis of surface morphological features is performed for graphene flakes and crystal particles. Raman analysis to the effects of FIB treatment for different materials shows large differences depending on the investigated material. Raman characterization with FIB milling on silicon substrates shows changes in the crystal lattice bond strength and amorphization of the material surface layer. After FIB treatment of carbon based materials, namely polymers and cells, a strong light absorption is observed in subsequent Raman analysis of the amorphizised materials.

Specific studies are performed to the analysis of white blood cells, plasmonic nanostructures, and optical whispering gallery resonators. Cell type identification based on Raman micro-spectroscopy and combined SEM characterization of the surface morphology for different cell types is demonstrated. The interest in plasmonic nanostructures originates from the potentially very strong Raman signal enhancement (108x enhancement factor in hot spots). The achieved Raman enhancement is strongly dependent on the nanostructure morphology, as characterized by SEM. The study to the optical response from WGM resonators started with a sudden observation of optical resonances during Raman analysis of polystyrene beads after SEM irradiation of these beads. Characterization has revealed that the beads function as WGM resonators, whose resonance spectra become visible after SEM irradiation.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Twente
  • Terstappen, Leon, Supervisor
  • Otto, Cees, Advisor
Thesis sponsors
Award date14 Sept 2017
Place of PublicationEnschede
Print ISBNs978-94-6233-719-0
Publication statusPublished - 14 Sept 2017


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