Iron-Mediated Growth of Graphene on SiC for Radiation Detection
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- Institutt for fysikk 
A proposed radiation sensor exploits graphene's high electron mobility and sensitivity to miniscule electric fields to attain a novel approach for radiation detection. Realizing such a sensor is contingent on controlled growth of high-quality graphene on a semiconductor with an insulating interlayer. It has been shown that treating silicon carbide with iron prior to annealing reduces graphitization temperature to ~600 degrees celsius along with the formation of an iron silicide interlayer. In this thesis the appropriateness of the SiC-FeSi-Gra system for forming radiation sensors was examined with regard to fabrication process and electrical properties. Graphene was grown in ultra-high vacuum on C-terminated SiC and characterized using X-ray photoelectron spectroscopy (XPS). The presence of graphene with a 30 degree rotation with respect to the substrate was confirmed by low-energy electron diffraction. Quantitative analysis on XPS data showed that approximately one monolayer of graphene was grown. Samples were successfully patterned by evaporating iron through a shadow mask, and the presence of graphene selectively on exposed regions was confirmed by spatially resolved XPS. A Hall bar was formed by patterned evaporation of iron for graphene growth, and silver for contacts. Hall measurements were carried out on the device, however inconclusive results were obtained due to poor electrical contact. Photoconductance measurements showed no clear improvement in conductance under exposure to light. Ab-initio calculations on the system suggest that the first layer of graphene interacts strongly with the underlying iron silicide layer forming a metallic buffer layer. It is hence suggested that a thicker film of graphene is grown for successful electrical measurements.