Distinctive Field-Effect Transistors and Ternary Inverters Using Cross-Type WSe₂/MoS₂ Heterojunctions Treated with Polymer Acid

Abstract

The electrical and optical characteristics of two-dimensional (2D) transition-metal dichalcogenides (TMDCs) can be improved by surface modification. In this study, distinctive field-effect transistors (FETs) were realized by forming cross-type 2D WSe2/MoS2 p–n heterojunctions through surface treatment using poly­(methyl methacrylate-co-methacrylic acid) (PMMA-co-PMAA). The FETs were applied to new ternary inverters as multivalued logic circuits (MVLCs). Laser confocal microscope photoluminescence spectroscopy indicated the generation of trions in the WSe2 and MoS2 layers, and the intensity decreased after PMMA-co-PMAA treatment. For the cross-type WSe2/MoS2 p–n heterojunction FETs subjected to PMMA-co-PMAA treatment, the channel current and the region of anti-ambipolar transistor characteristics increased considerably, and ternary inverter characteristics with three stable logic states, “1”, “1/2”, and “0”, were realized. Interestingly, the intermediate logic state 1/2, which results from the negative differential transconductance characteristics, was realized by the turn-on of all component FETs, as the current of the FETs increased after PMMA-co-PMAA treatment. The electron-rich carboxyl acid moieties in PMMA-co-PMAA can undergo coordination with the metal Mo or W atoms present in the Se or S vacancies, respectively, resulting in the modulation of charge density. These features yielded distinctive FETs and ternary inverters for MVLCs using cross-type WSe2/MoS2 heterojunctions.

Recent progress in 2D hybrid heterostructures from transition metal dichalcogenides and organic layers: properties and applications in energy and optoelectronics fields

“…Beyond the effects on individual TMD layers, organic functionalization may also control the electronic properties of TMD-based heterostructures. 33,94 For example, Kim et al reported that the hole conductance of WSe 2 /MoS 2 p–n heterojunction FETs may be enhanced by functionalizing poly(methyl methacrylate- co -methacrylic acid) (PMMA- co -PMAA) on the TMD heterolayers (Fig. 6e).…”

“…38,92 Lastly, it was recently reported that the organic functionalization may tailor not only the properties of the individual layer but also the interlayer interaction in TMD-based heterojunctions such as TMD/TMD, TMD/graphene, and TMD/hBN. 90,93,94 The organic layers embedded in the multicomponent heteroassemblies can control the interlayer charge and energy transfer. 93,94 The embedded molecular systems also modify the emission characteristics of IXs in TMD/TMD heterostructures by converting the charge transfer pathways from tunneling to type-II-junction-supported transport and modulating the dielectric screening strength.…”

Charge-Transfer Effect and Enhanced Photoresponsivity of WS2- and MoSe2-Based Field Effect Transistors with π-Conjugated Polyelectrolyte

“…The TR-PL spectra were obtained using a time-correlated single-photon counting system. The LCM PL and TR-PL spectroscopy methods were reported in detail in previous works. , The optical absorption spectra of pristine and FPS-K-treated MoSe 2 and WS 2 samples were measured using an Agilent 8453 UV–vis spectrophotometer. The binding energies of the constituent atoms of the samples were measured using X-ray photoelectron spectroscopy (XPS; Nexsa).…”

Reconfigurable Multivalue Logic Functions of a Silicon Ellipsoidal Quantum-Dot Transistor Operating at Room Temperature

“…For instance, negative-differential conductance (NDC) devices and negative-differential transconductance (NDT) transistors, which comprise diverse kinds of materials ( e.g. , biomolecule complexes, − organic materials, − carbon nanotubes, graphene, , van der Waals heterostructures, − oxide composites, , silicon (Si) nanostructures, − etc . ), are typical examples that can realize the MVL computing system beyond modern binary digital technology.…”