Molybdenum Disulfide Field-effect Transistors Research Articles

On Monolayer ${\rm MoS}_{2}$ Field-Effect Transistors at the Scaling Limit

The ultimate scaling limit of double-gate molybdenum disulfide (MoS2) field-effect transistors (FETs) with a monolayer thin body is examined and compared with ultrathin-body Si FETs by self-consistent quantum transport simulation in the presence of phonon scattering. Modeling of phonon scattering, quantum mechanical effects, and self-consistent electrostatics allows us to accurately assess the performance potential of monolayer MoS2 FETs. The results revealed that monolayer MoS2 FETs show 52% smaller drain-induced barrier lowering (DIBL) and 13% smaller subthreshold swing (SS) than 3-nm-thick-body Si FETs at a channel length of 10 nm with the same gating. With a requirement of DIBL , the scaling limit of monolayer MoS2 FETs is assessed to be 8 nm, comparing with 10 nm of the ultrathin-body Si counterparts due to the monolayer thin body and higher effective mass, which reduces direct source-to-drain tunneling. By comparing with the international technology roadmap for semiconductor (ITRS) target for high performance logic devices of 2023; double-gate monolayer MoS2 FETs can fulfill the ITRS requirements.

Characteristics of a pressure sensitive touch sensor using a piezoelectric PVDF-TrFE/MoS2 stack

A new touch sensor device has been demonstrated with molybdenum disulfide (MoS2) field effect transistors stacked with a piezoelectric polymer, polyvinylidene fluoride–trifluoroethylene (PVDF–TrFE). The performance of two device stack structures, metal/PVDF–TrFE/MoS2 (MPM) and metal/PVDF–TrFE/Al2O3/MoS2 (MPAM), were compared as a function of the thickness of PVDF–TrFE and Al2O3. The sensitivity of the touch sensor has been improved by two orders of magnitude by reducing the charge scattering and enhancing the passivation effects using a thin Al2O3 interfacial layer. Reliable switching behavior has been demonstrated up to 120 touch press cycles.

Modulating electronic transport properties of MoS2 field effect transistor by surface overlayers

In situ bottom-gated molybdenum disulfide (MoS2) field effect transistors (FETs) device characterization and in situ ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy measurements were combined to investigate the effect of surface modification layers of C60 and molybdenum trioxide (MoO3) on the electronic properties of single layer MoS2. It is found that C60 decoration keeps MoS2 FET performance intact due to the very weak interfacial interactions, making C60 as an ideal capping layer for MoS2 devices. In contrast, decorating MoO3 on MoS2 induces significant charge transfer at the MoS2/MoO3 interface and largely depletes the electron charge carriers in MoS2 FET devices.

Electrical performance of monolayer MoS2 field-effect transistors prepared by chemical vapor deposition

Molybdenum disulfide (MoS2) field effect transistors (FET) were fabricated on atomically smooth large-area single layers grown by chemical vapor deposition. The layer qualities and physical properties were characterized using high-resolution Raman and photoluminescence spectroscopy, scanning electron microscopy, and atomic force microscopy. Electronic performance of the FET devices was measured using field effect mobility measurements as a function of temperature. The back-gated devices had mobilities of 6.0 cm2/V s at 300 K without a high-κ dielectric overcoat and increased to 16.1 cm2/V s with a high-κ dielectric overcoat. In addition the devices show on/off ratios ranging from 105 to 109.

Harmonic and intermodulation performance of MoS2FET- and GFET-based amplifiers

This paper presents a simple mathematical model for the output---input voltage characteristic of the graphene field effect transistor (GFET)- and the molybdenum disulfide field effect transistor (MoS2FET)-based inverting amplifiers. The model, basically a Fourier series, yields closed-form expressions for the amplitudes of the harmonic and intermodulation components of the output voltage resulting from a multisinusoidal input voltage. The special case of a two-tone equal-amplitude input voltage is considered in detail. The results show that the harmonic and intermodulation performance of the complementary GFET- and the MoS2FET-based inverting amplifiers is strongly dependent on the bias voltage and the amplitudes of the input tones with the third-order intermodulation component dominating over a wide range of the input voltage amplitudes.

Oxygen environmental and passivation effects on molybdenum disulfide field effect transistors

We investigated the effects of passivation on the electrical characteristics of molybdenum disulfide (MoS2) field effect transistors (FETs) under nitrogen, vacuum, and oxygen environments. When the MoS2 FETs were exposed to oxygen, the on-current decreased and the threshold voltage shifted in the positive gate bias direction as a result of electrons being trapped by the adsorbed oxygen at the MoS2 surface. In contrast, the electrical properties of the MoS2 FETs changed only slightly in the different environments when a passivation layer was created using polymethyl methacrylate (PMMA). Specifically, the carrier concentration of unpassivated devices was reduced to 6.5 × 1015 cm−2 in oxygen from 16.3 × 1015 cm−2 in nitrogen environment. However, in PMMA-passivated devices, the carrier concentration remained nearly unchanged in the range of 1–3 × 1015 cm−2 regardless of the environment. Our study suggests that surface passivation is important for MoS2-based electronic devices.