Contacts for Molybdenum Disulfide: Interface Chemistry and Thermal Stability

Abstract

In this review on contacts with MoS2, we consider reports on both interface chemistry and device characteristics. We show that there is considerable disagreement between reported properties, at least some of which may be explained by variability in the properties of geological MoS2. Furthermore, we highlight that while early experiments using photoemission to study the interface behavior of metal-MoS2 showed a lack of Fermi-level pinning, device measurements repeatedly confirm that the interface is indeed pinned. Here we suggest that a parallel conduction mechanism enabled by metallic defects in the MoS2 materials may explain both results. We note that processing conditions during metal depositions on MoS2 can play a critical role in the interface chemistry, with differences between high vacuum and ultra-high vacuum being particularly important for low work function metals. This can be used to engineer the interfaces by using thin metal-oxide interlayers to protect the MoS2 from reactions with the metals. We also report on the changes in the interfaces that can occur at high temperature which include enhanced reactions between Ti or Cr and MoS2, diffusion of Ag into MoS2, and delamination of Fe. What is clear is that there is a dearth of experimental work that investigates both the interface chemistry and device properties in parallel.

The electronic states of ITO–MoS2: Experiment and theory

“…In this regard, Schottky barrier height (SBH) and partial Fermi level pinning play a significant role for chemical contact between semiconductor-metal interfaces during operation. [8,9] Some of most used contact materials in semiconductor-based devices are gold, titanium, platinum, and nickel due to their low resistivity and chemical compatibility with semiconductors.…”

Low-frequency Raman signature of Ag-intercalated few-layer MoS2

“…For MoS 2 to be usable in future nanoscale electronics, low-resistance Ohmic contacts need to be achieved and understood well. Reducing the contact resistance has been explored experimentally using many approaches [4][5][6]. One such method employs an annealing procedure performed to dope few-layer MoS 2 from a metallic contact such as silver [7].…”

Graphene/molybdenum disulfide nanocomposites: characterization and optoelectronic application

“…1). 8,10 Moreover, it appears in nature as an n-type material, 11 with visible to near-infrared light absorption, 9 a large work function of 5.1 eV, 12 and mechanical stability and transparency for flexible devices. 8 The most attractive feature of MOS 2 is the variable energy gap from 1.2 to 1.8 eV as the material moves from the bulk indirect bandgap to the direct bandgap monolayer due to the quantum confinement effect.…”