Raman Spectroscopy of 2D Materials: Under Non-Ambient Conditions

One of the foundations of modern electronics is the targeted introduction of defects to change material properties. Researchers have been working for years to harness the special properties of 2D materials in devices such as gas sensors, LEDs or wearable biosensor systems. Raman spectroscopy plays an important role in the rapid and non-destructive analysis of the (opto-)electronic properties of these layers. Ion bombardment can also be used here to modify the 2D layers in such a way as to adapt their properties to specific functions. This is still the subject of current research. The exact mechanisms of interaction between the ion bombardment, the saturation of the defects with adsorbates and the resulting change in material properties are not fully understood. Current analytical methods can only record the ‘before’ and ‘after’ state, but not the intermediate state after defect creation and before saturation. This dissertation presents different possibilities to perform Raman spectroscopy under non-ambient conditions. Five different vacuum chambers are presented, covering different applications in the modification and especially the analysis of 2D layers. On the one hand, a new chamber was set up to enable the irradiation of samples with low-energy Ar+ ions. Two smaller chambers are presented with which electrical measurements and Raman spectroscopy can be carried out simultaneously on samples in a vacuum (or under the influence of gas). The main task, however, was the construction and commissioning of a portable Raman spectrometer that can perform in-situ measurements in a vacuum. This system was first tested on an existing beamline for highly charged ions at the University of Duisburg-Essen. The Raman system was then transported to the GSI particle accelerator in Darmstadt. There, a new vacuum chamber was built on the CRYRING storage ring as part of this work. This allows swift heavy ion irradiation and subsequent in-situ Raman measurements. These chambers were commisioned and initial measurements were carried out. The in-situ measurements in particular have shown that these measurements are necessary. When graphene was irradiated with highly charged Xe ions, a change in doping was observed in-situ. After contact with air, this change returned to the original doping.