INVESTIGATION OF MOLECULE/INORGANIC INTERFACES USING LOW-TEMPERATURE SCANNING TUNNELING MICROSCOPY

Abstract

Two-dimensional semiconductors such as two-dimensional transition metal dichalcogenides, organic molecules and phosphorene like materials have recently gained much interest in the scientific community. 2D semiconductors are usually supported by substrates (metal, semi-metal, semiconductor or insulator), hence it is crucial to understand how the substrate interacts with the 2D semiconductor on top. In this thesis, we investigate the interface between organic semiconducting molecules (F4TCNQ) and three types of substrates (Au(111), HOPG, monolayer-MoSe2). First, we used LT-STM to image the self-assembly process of F4TCNQ molecules on the above-mentioned three substrates. On the Au(111) surface, F4TCNQ molecules form a metal-organic network with Au atoms, while the close packing structures of F4TCNQ on HOPG and MoSe2 are similar to each other. Further STS measurements show significant change of the HOMO-LUMO gap on different substrates, which can be attributed to the charge transfer and screening effect of the substrate. In the last part of the thesis, we investigate the formation of antimonene on Au(111) which consists of several intermediate states. At low coverage (~0.1ML), dimer arrays of Sb4 molecules are observed. At higher coverage, more Sb4 molecules accumulate randomly on the surface and they no longer have periodicity. Stable AuSb2 alloy forms at higher coverage.