Impact of fast transient charging and ambient on mobility of WS2 field-effect transistor

Park, Junghak; Woo, Hyunsuk; Jeon, Sanghun

doi:10.1116/1.4989781

Cited by 8 publications

(3 citation statements)

References 50 publications

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“…High-quality single-crystal monolayer WS 2 is essential for the excellent performance of field-effect transistors (FETs). , The optimized uniform structure enables high carrier mobility throughout the structure with reduced effective mass of electrons. Compared with the mechanically exfoliated WS 2 sample with a limited size (∼20 μm) and uncontrolled thickness, CVD-grown monolayer WS 2 exhibits a low on/off ratio and poor electron mobility in FETs, mainly owing to the presence of structural defects and poor uniformity. , …”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional High-Quality Monolayered Triangular WS₂ Flakes for Field-Effect Transistors

Yue¹,

Chen²,

Zhang

et al. 2018

ACS Appl. Mater. Interfaces

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Large-area uniform of single-crystal tungsten disulfide (WS) is important for advanced optoelectronics based on two-dimensional (2D) atomic crystals. However, difficulties in controlling the interrelated growth parameters restrict its development in devices. Herein, we present the synthesis of triangular monolayered WS flakes with good uniformity and single crystal by adjusting the introduction time of sulfur precursor and the distances between the sources and substrates to control the nucleation density. Investigation of the morphology and structure by transmission electron microscopy and Raman spectroscopy indicates that a series of triangular (side length of 233 μm) monolayered WS flakes shows high-quality structure and homogenous crystallinity. Field-effect transistors based on the fabricated triangular monolayered WS with single crystal demonstrate environmentally stable charge transport with a field-effect mobility of 50.5 cm/V s and current modulation I/ I of ∼10. The results of this study pave the way for the application of monolayered WS in a multitude of 2D-material-based devices.

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Section: Introductionmentioning

confidence: 99%

Two-Dimensional High-Quality Monolayered Triangular WS₂ Flakes for Field-Effect Transistors

Yue¹,

Chen²,

Zhang

et al. 2018

ACS Appl. Mater. Interfaces

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“…The opaque as well as transparent Ti/Au metal electrodes were deposited using an electron beam evaporator to form the source and drain electrodes of the TFT. The as-fabricated TFTs were annealed at 200 °C for 2 h to remove the residual solvents, as well as to minimize the contact resistance of the metal semiconductor junction [30].…”

Section: Methodsmentioning

confidence: 99%

Broad spectral responsivity in highly photoconductive InZnO/MoS₂ heterojunction phototransistor with ultrathin transparent metal electrode

et al. 2019

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An amorphous InZnO/MoS2 heterojunction-based phototransistor with excellent photoconductive gain and responsivity over the entire visible range has been demonstrated. The photogenerated current of the InZnO phototransistor at long light wavelength (>600 nm) was significantly improved by utilizing narrow bandgap MoS2 as the capping layer (1.3 eV). At lower wavelength, photocarriers are generated due to the optical absorption of both InZnO and MoS2 layers, whereas the latter ensures significant photocarrier generation even at the higher wavelength region of the visible spectrum. The photogenerated carriers subsequently transfer to the underlying InZnO layer of superior carrier mobility that has a high channel conduction of additional electrons from the optically-induced doubly positively charged oxygen vacancies (Vo++) where the gate field is screening, thereby leading to the higher photoconductive gain of the InZnO/MoS2 phototransistors. The dynamic photosensitivity behaviour of the aforesaid phototransistor reveals the presence of persistent photoconductivity (PPC) due to the oxygen vacancy associated with InZnO which can be removed by applying a reset gate pulse from −15 to +5 V. The optical properties of these phototransistors were further enhanced by replacing the opaque Ti/Au electrode by an ultrathin transparent Ti/Au electrode. Utilization of the transparent electrode results in enhanced electron injection from source to channel due to a reduced barrier height under illumination giving rise to a ten-fold improvement in the photocurrent and responsivity of the phototransistors. A position-dependent study of the photocurrent w.r.t beam position also reveals that the enhancement in photocurrent is strongly dependent on the position and is at its maximum when the beam is placed near the source region.

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“…Unlike graphene, the appearance of transition metal dichalcogenides (TMDCs) including MoS 2 , WS 2 and WSe 2 , which have semiconductor properties, have received significant attention for use as a transistor channel [4][5][6][7][8]. Among the TMDCs, MoS 2 has outstanding electrical properties, for example, high mobility, a large on/off current ratio, lowtemperature processing, and an ultralow standby power consumption [9,10].…”

Section: Introductionmentioning

confidence: 99%

Quantitative analysis of charge trapping and classification of sub-gap states in MoS₂ TFT by pulse I–V method

2018

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The threshold voltage instabilities and huge hysteresis of MoS thin film transistors (TFTs) have raised concerns about their practical applicability in next-generation switching devices. These behaviors are associated with charge trapping, which stems from tunneling to the adjacent trap site, interfacial redox reaction and interface and/or bulk trap states. In this report, we present quantitative analysis on the electron charge trapping mechanism of MoS TFT by fast pulse I-V method and the space charge limited current (SCLC) measurement. By adopting the fast pulse I-V method, we were able to obtain effective mobility. In addition, the origin of the trap states was identified by disassembling the sub-gap states into interface trap and bulk trap states by simple extraction analysis. These measurement methods and analyses enable not only quantitative extraction of various traps but also an understanding of the charge transport mechanism in MoS TFTs. The fast I-V data and SCLC data obtained under various measurement temperatures and ambient show that electron transport to neighboring trap sites by tunneling is the main charge trapping mechanism in thin-MoS TFTs. This implies that interfacial traps account for most of the total sub-gap states while the bulk trap contribution is negligible, at approximately 0.40% and 0.26% in air and vacuum ambient, respectively. Thus, control of the interface trap states is crucial to further improve the performance of devices with thin channels.

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Impact of fast transient charging and ambient on mobility of WS2 field-effect transistor

Cited by 8 publications

References 50 publications

Two-Dimensional High-Quality Monolayered Triangular WS₂ Flakes for Field-Effect Transistors

Two-Dimensional High-Quality Monolayered Triangular WS₂ Flakes for Field-Effect Transistors

Broad spectral responsivity in highly photoconductive InZnO/MoS₂ heterojunction phototransistor with ultrathin transparent metal electrode

Quantitative analysis of charge trapping and classification of sub-gap states in MoS₂ TFT by pulse I–V method

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Impact of fast transient charging and ambient on mobility of WS2 field-effect transistor

Cited by 8 publications

References 50 publications

Two-Dimensional High-Quality Monolayered Triangular WS2 Flakes for Field-Effect Transistors

Two-Dimensional High-Quality Monolayered Triangular WS2 Flakes for Field-Effect Transistors

Broad spectral responsivity in highly photoconductive InZnO/MoS2 heterojunction phototransistor with ultrathin transparent metal electrode

Quantitative analysis of charge trapping and classification of sub-gap states in MoS2 TFT by pulse I–V method

Contact Info

Product

Resources

About

Two-Dimensional High-Quality Monolayered Triangular WS₂ Flakes for Field-Effect Transistors

Two-Dimensional High-Quality Monolayered Triangular WS₂ Flakes for Field-Effect Transistors

Broad spectral responsivity in highly photoconductive InZnO/MoS₂ heterojunction phototransistor with ultrathin transparent metal electrode

Quantitative analysis of charge trapping and classification of sub-gap states in MoS₂ TFT by pulse I–V method