Pinch-Off Formation in Monolayer and Multilayers MoS2 Field-Effect Transistors

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.

Machine Learning Analysis of Raman Spectra of MoS2

“…As shown in Figure 1c, two Raman-active modes, E 1 2g and A 1g , exhibit significant differences, and the Raman frequency difference of the monolayer sample is~17.9 cm −1 , while that of the bilayer sample is~21.1 cm −1 . This is consistent with previous results for mechanical exfoliation (ME)-prepared and CVD-prepared samples, implying this difference is universal between samples obtained from different preparation methods [35][36][37]. The cracks nucleated at sulfur vacancies propagate along the energy-favored zigzag directions upon the relatively fast temperature-drop-induced thermal strain, which results in an orientation-specific fracture behavior [38].…”

Direct Observation of Charge Transfer between NOx and Monolayer MoS2 by Operando Scanning Photoelectron Microscopy

“…The local BE of the core levels is a direct probe of the potential distribution of electrons between the source and drain. The maps in Figure b,c show shifts in the Mo 3d peak position along the channel, from 230.3 eV at the source contact at the top (located just outside the frame of the maps) to 229.3 eV at the drain contact at the bottom, within the range set by the applied V d = 1 V. Most of the potential drop is known to occur in the regions close to the metallic contacts …”

“…The maps in Figure 4b,c show shifts in the Mo 3d peak position along the channel, from 230.3 eV at the source contact at the top (located just outside the frame of the maps) to 229.3 eV at the drain contact at the bottom, within the range set by the applied V d = 1 V. Most of the potential drop is known to occur in the regions close to the metallic contacts. 23 Spatial inhomogeneity in the direction perpendicular to the applied bias can be observed in the maps. In the region close to the source contact, the lateral injection region formed by the Schottky contact between Ti/Au and MoS 2 is easily observed as a blue V-shaped region of high BE peak positions.…”

Three-Dimensional Kelvin Probe Force Microscopy

“…It utilizes the long-range electrostatic force between a probe and a sample as feedback to perform measurements that combine noncontact atomic force microscopy (AFM) and the Kelvin method based on the “nulling” concept. , The SP of the sample can be obtained form the contact potential difference (CPD) between the tip and sample directly acquired by KPFM, when the SP of the tip is known . Benefiting from its high spatial resolution, few environmental constraints, and good developability, KPFM has been applied in many fields such as biomolecules, , semiconductor materials, , optoelectronic devices, , and so forth. For example, Sinensky et al adopted KPFM to analyze a protein/DNA nanoarray, resolving three nucleotide mismatches with high resolution, sensitivity, and speed .…”