Layer-Thickness-Dependent Work Function of MoS₂ on Metal and Metal Oxide Substrates

Abstract

Transition metal dichalcogenides, such as molybdenum disulfide (MoS 2 ), have unique electronic and optoelectronic properties that are often altered by environmental effects, particularly substrate or contact materials. Understanding these effects is important for device design and engineering. There is limited information concerning how MoS 2 interacts with 3D semiconductors such as metal oxides. This work demonstrates the influence of substrate material and MoS 2 layer thickness on the work function of exfoliated MoS 2 flakes. Kelvin probe force microscopy is used to probe the work function of MoS 2 on titanium oxide (TiO x ), molybdenum oxide (MoO x ), and gold (Au). We find that TiO x based substrates yield a lower MoS 2 work function than MoO x and Au for various MoS 2 thicknesses, and that the screening lengths for each substrate are larger than 5 nm. By reporting the work function variation of MoS 2 on these substrates, this study aims to provide important insights into device design and contact engineering.

Orientation of Cobalt-Phthalocyanines on Molybdenum Disulfide: Distinguishing between Single Crystals and Small Flakes

“…61 However, and most importantly, all methods agree in that the work function increases from single to few-layer MoS 2 . 54,61,62 Using PEEM under UHV conditions, for MoS 2 on oxidized silicon, differences of 60 and 80 meV were observed from 1 to 2 and 2 to3 monolayers, respectively. Thus, the lower work function of regions R3 and R4 in Figure 2b, c clearly indicates a lower number of MoS 2 layers.…”

“…33 However, for monolayer or few-layers on oxidized silicon, significantly lower values were observed (Φ ∼ 4.5 eV) by both PEEM and Kelvin probe force microscopy (KPFM). 60,61 We note that KPFM measures relative work functions, which may complicate a direct comparison of the absolute values. Furthermore, a comparison to literature data has to take into account difference in the preparation method, the influence of contaminations in the case of measurements under ambient conditions, 60 as well as the choice of the substrate, which may alter the work function of MoS 2 flakes by several tenths of eV.…”

Two-Dimensional Layered Materials Meet Perovskite Oxides: A Combination for High-Performance Electronic Devices

“…A representative example of this type of charge transfer is the one that exists in the La 0.7 Sr 0.3 MnO 3 -MoS 2 heterojunction . La 0.7 Sr 0.3 MnO 3 is a metallic perovskite oxide with a relatively large work function (4.8 eV), and MoS 2 is an n-type semiconductor with a smaller work function (4.4–4.5 eV) dependent on the substrates from the 2DLM family. In contact, electrons transfer from MoS 2 to La 0.7 Sr 0.3 MnO 3 and the resulting built-in electric field can be exploited for diode devices .…”

Coating of gallium-based liquid metal particles with molybdenum oxide and oxysulfide for electronic band structure modulation

“…31,32 The band gap in MoS 2 varies from an indirect band gap of 1.2 in its bulk to a direct band gap of 1.8 eV as a monolayer. 33,34…”

“…31,32 The band gap in MoS 2 varies from an indirect band gap of 1.2 in its bulk to a direct band gap of 1.8 eV as a monolayer. 33,34 LM-based processes, such as heterostructuring, alloying, sonication and transformations, can be used for the incorporation of materials and metal oxides at the nanoscale. 12 Subsequently, developing roadmaps towards fabricating LMbased heterostructures with MoO x and MoS x coatings, with ondemand properties and a broad range of functional applications in photocatalysis, optics, flexible electronics, and energy storage, is possible.…”