Effects of Annealing on Electrode/MoS ₂ Interfaces Studied by Photoelectron Spectroscopy

For optoelectronic devices based on transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2), contacts with metal electrode materials are of great importance. However, the role of possible interactions at these interfaces for the device performance is often not sufficiently considered. We present an in-depth study of interface properties between MoS2 and Au, Cu, and Ti using photoelectron spectroscopy (PES) and scanning electron microscopy (SEM). By postdeposition annealing, we simulate the potential long-term effects of slow metal diffusion into MoS2. A doping of the TMDC was observed at the Au- and Cu-containing interfaces, as well as the (partial) diffusion of metal atoms into the TMDC substrate after annealing. In the case of Ti, we observe profound changes in the electronic structure, indicating a chemical reaction. The deposition of cobalt(II)-hexadecafluorophthalocyanine (CoPcF16) on the metal-covered surface was utilized as a probe for the presence of metal atoms on the topmost TMDC layer before and after annealing.