The THz regime is the bridge between optics and electronics. THz radiation is non-ionizing and non-invasive and can be used for various, especially for imaging. However, the THz wavelength is between 3 mm and 30 um, so it is challenging for nano-scale imaging. In this work, we will use an in-house-built THz scanning near-field microscope (THz-sSNOM) to characterize graphene on thin films of cyclic ole-fin copolymer - TOPAS) (figure 1). While graphene has been studied mainly on a silicon substrate, twisted graphene is a novel material, and its promising THz properties have not been thoroughly in-vestigated yet. During this project, the student will characterize both materials and compare the physi-cal properties, such as conductivity and mobility on various substrates, in the THz regime. Moreover, the project aims to efficiently map the graphene transfer process on TOPAS using these THz tech-niques.
We are looking for motivated students with a background in physics, material science, electrical engi-neering, or chemistry for an MSc thesis in Transport at Nanoscale Interfaces Laboratory at Empa.

During the project, the MSc student will work on the following:

• Nanoimaging with THz-sSNOM
• Graphene transfer
• Raman Spectroscopy
• THz time-domain spectroscopy
• Matlab/python for analyzing data

Figure 1. Blender illustration of THz-sSNOM.

Transfer of graphene and twisted graphene on polymers and comparison of THz properties (conductivity and mobility) in nanoscale of twisted graphene in comparison with graphene.

Interested candidates can send an email with their CVs with a short motivation letter to Dr. Elena Mavrona (eleni.mavrona@empa.ch); also, they can contact her if they need further information.

• Maissen et al., Probes for Ultrasensitive THz Nanoscopy, ACS Photonics 2019, 6, 5, 1279–1288
• Zhang et al., Terahertz Nanoimaging of Graphene, ACS Photonics 2018, 5, 7, 2645–2651