Investigating charge traps in MoTefield-effect transistors: SiOinsulator traps and MoTebulk traps.

Two-dimensional material-based field-effect transistors are promising for future use in electronic and optoelectronic applications. However, trap states existing in the transistors are known to hinder device performance. They capture/release carriers in the channel and lead to hysteresis in the transfer characteristics.

One-Step Passivation of Both Sulfur Vacancies and SiO Interface Traps of MoS Device.

Transition metal dichalcogenides (TMDs) benefit electrical devices with spin-orbit coupling and valley- and topology-related properties. However, TMD-based devices suffer from traps arising from defect sites inside the channel and the gate oxide interface. Deactivating them requires independent treatments, because the origins are dissimilar.

Optical Duality of Molybdenum Disulfide: Metal and Semiconductor.

The two different light-matter interactions between visible and infrared light are not switchable because control mechanisms have not been elucidated so far, which restricts the effective spectral range in light-sensing devices. In this study, modulation of the effective spectral range is demonstrated using the metal-insulator transition of MoS. Nondegenerate MoS exhibits a photoconductive effect in detecting visible light.

Edge Contact for Carrier Injection and Transport in MoS Field-Effect Transistors.

The contact properties of van der Waals layered semiconducting materials are not adequately understood, particularly for edge contact. Edge contact is extremely helpful in the case of graphene, for producing efficient contacts to vertical heterostructures, and for improving the contact resistance through strong covalent bonding. Herein, we report on edge contacts to MoS of various thicknesses.

Temperature-Dependent Opacity of the Gate Field Inside MoS Field-Effect Transistors.

The transport behaviors of MoS field-effect transistors (FETs) with various channel thicknesses are studied. In a 12 nm thick MoS FET, a typical switching behavior is observed with an / ratio of 10. However, in 70 nm thick MoS FETs, the gating effect weakens with a large off-current, resulting from the screening of the gate field by the carriers formed through the ionization of S vacancies at 300 K.

Semimetallic Graphene for Infrared Sensing.

Both photothermal and photovoltaic infrared (IR) detectors employ sensing materials that have an optical band gap. Different from these conventional materials, graphene has a conical band structure that imposes zero band gap. In this study, using the semimetallic multilayer graphene, IR detection at room temperature is realized.

Defect-Affected Photocurrent in MoTe FETs.

Imperfections in the crystal lattice, such as defects, grain boundaries, or dislocations, can significantly affect the optical and electrical transport properties of materials. In this study, we report the effect of mid gap trap states on photocurrent in 10 atomic layered 2H-MoTe. Our study reveals that the photocurrent is very sensitive to the number of active traps, which can be controlled by V.

Tunable Mobility in Double-Gated MoTe Field-Effect Transistor: Effect of Coulomb Screening and Trap Sites.

There is a general consensus that the carrier mobility in a field-effect transistor (FET) made of semiconducting transition-metal dichalcogenides (s-TMDs) is severely degraded by the trapping/detrapping and Coulomb scattering of carriers by ionic charges in the gate oxides. Using a double-gated (DG) MoTe FET, we modulated and enhanced the carrier mobility by adjusting the top- and bottom-gate biases. The relevant mechanism for mobility tuning in this device was explored using static DC and low-frequency (LF) noise characterizations.

Photocurrent Switching of Monolayer MoS Using a Metal-Insulator Transition.

We achieve switching on/off the photocurrent of monolayer molybdenum disulfide (MoS) by controlling the metal-insulator transition (MIT). N-type semiconducting MoS under a large negative gate bias generates a photocurrent attributed to the increase of excess carriers in the conduction band by optical excitation. However, under a large positive gate bias, a phase shift from semiconducting to metallic MoS is caused, and the photocurrent by excess carriers in the conduction band induced by the laser disappears due to enhanced electron-electron scattering.