Abstract
The discovery of layered materials, including transition metal dichalcogenides (TMD), gives rise to a variety of novel nanoelectronic devices, including fast switching field-effect transistors (FET), assembled heterostructures, flexible electronics, etc. Molybdenum disulfide (MoS2), a transition metal dichalcogenides semiconductor, is considered an auspicious candidate for the post-silicon era due to its outstanding chemical and thermal stability. We present a Kelvin probe force microscopy (KPFM) study of a MoS2 FET device, showing direct evidence for pinch-off formation in the channel by in situ monitoring of the electrostatic potential distribution along the conducting channel of the transistor. In addition, we present a systematic comparison between a monolayer MoS2 FET and a few-layer MoS2 FET regarding gating effects, electric field distribution, depletion region, and pinch-off formation in such devices.
Highlights
Two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides (TMDs), attract extensive interest from the research community as they are considered as possible candidates for post-silicon electronics [1]
Monolayer and few-layer MoS2 samples were transferred on top of an 8 mm square dye made of a highly doped P-type silicon wafer covered by a 90 nm silicon oxide (SiO2) layer via the mechanical exfoliation with scotch tape, initially developed for graphene [35], of MoS2 crystals supplied by Structure Probe Inc. (SPI) Supplies (West Chester, PA, USA)
We presented a direct observation of pinch-off region formation in monolayer and multilayer MoS2 field-effect transistors (FET) through a detailed analysis of the electrostatic potential distribution along the devices
Summary
Two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides (TMDs), attract extensive interest from the research community as they are considered as possible candidates for post-silicon electronics [1]. Nipane et al [21] modeled the electrostatics of lateral junctions in atomically thin materials using line charges representation, Sohn et al [22] investigated the electrostatic band alignment at Au/MoS2 contacts as a function of the thickness of MoS2 exfoliated flakes, and Chiu et al [23] determined the band alignment in single-layer MoS2/WSe2 heterojunctions using micro X-ray photoelectron spectroscopy and scanning tunneling microscopy (STM). Other groups have measured the built-in potential of single-layer MoS2 heterojunctions using KPFM [30] and demonstrated the electrical properties of the contact between MoS2 and different metals [31]. These measurements resemble the use of KPFM for contact resistance evaluation [32] and contact-free mobility estimation [33] in thin-film organic transistors
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