Investigation of lithographic residues by SERS method at graphene field effect transistors

It is thought that foreign atoms or molecules which are produced by lithographic process can stay on graphene surface in the fabrication process of circuit elements which are made from graphene. In particular, photoresist residues are emerging as the biggest limiting factor of efficiency of graphene based circuit elements which can operate with theoretically calculated 200,000 cm2/Vs electron mobility. Furthermore, only a few thousand cm2/Vs experimentally obtained mobility values make this problem more important. In this thesis, our motivation source is lithographic residue problem which is often mentioned in the literature and litographic residues which are remain but cannot be observed by optical microscopy on the graphene surface are investigated and proven the existance of residues by a powerful method in terms of quality as the SERS. It is found that when lift-off applied surfaces exposed to oxygen or hydrogen gas under ultraviolet light, the procedure makes residues optical visible. Furthermore, a resist-solvent which can reduce litographic residues is investigated and found. At the all processes, different solvents are used and lift-off process is performed. The fabricated samples are compared with each other in terms of electrical characteristics. Keywords: Graphene, Lithography, Photoresist, Mobility, SERS