(Invited) Impact of Substrates and Interfaces on 2D TMDC Properties

Abstract

2D TMDCs show promise to multiple applications, from distributed systems, to optical devices, and high-performance electronics. Nonetheless, how these ultra-thin semiconductors are impacted by their encapsulating environment / interfacial interactions is still a matter of discussion. Challenges relate to how to characterize dielectric surface related interactions, and how to assess the interface quality (quickly and in-line). We will discuss the impact of substrates / interfaces on electrical and optical properties of TMDCs and identify which parameters are the main affecting factors.We show that defect bands from the dielectric substrate can result in doping or in loss of ambipolarity, depending on their position relative to the band gap of the 2D TMDC. From correlations between AFM and Raman maps, we show that nanoscale strain and doping are closely linked, which is confirmed by conductive AFM measurements. To assess substrate defectivity and the impact of trapped species, we demonstrate a novel and simple method, which relies on indirect band gap transitions.Finally, we demonstrate that by understanding the multiple mechanisms of Fermi level pinning and controlling both contact and dielectric interface, ambipolarity can be demonstrated in MoS2 flakes.