Ultimate dielectric scaling of 2D transistors via van der Waals metal integration

Dang, Weiqi; Zhao, Bei; Liu, Chang; Yang, Xiangdong; Kong, Lingan; Lu, Zheyi; Li, Bo; Li, Jia; Zhang, Hongmei; Li, Wanying; Shi, Shun; Qin, Ziyue; Liao, Lei; Duan, Xidong; Liu, Yuan

doi:10.1007/s12274-021-3708-1

Cited by 22 publications

(10 citation statements)

References 45 publications

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“…In modern technology, highly efficient and broadband photodetectors are demanded due to their compelling applications in fiber optic communication, energy harvesting, environmental/health monitoring, and medical image processing . Nevertheless, most economical broadband photodetectors are based on single-crystal semiconductors including Si, GaAs, and InGaAs, which have complex and costly production processes, high operating voltage, and low responsivity, iterating the necessity of a new class of broadband photodetectors. , Two-dimensional materials and especially transition metal dichalcogenides (TMDs) are considered as potential for applicants a new generation of electronic and optoelectronic devices by reason of their unique characteristics of thin-layer exfoliation capability, free dangling bonds, layer-dependent properties, and high carrier mobility, which are absent in their bulk counterparts. Tungsten diselenide (WSe 2 ) is one of the TMD materials with a band gap in the range of ∼1.2 (indirect band gap in a multilayer) to ∼1.8 eV (direct band gap in a monolayer), which among other TMDs such as MoS 2 , WS 2 , and MoSe 2 has not been investigated much.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Broadband Photoresponsivity of the CZTS/WSe₂ Heterojunction by Gate Voltage

Ghods

Vardast

Esfandiar

et al. 2022

ACS Appl. Electron. Mater.

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High-performance photodetectors play critical roles in numerous photon-based applications in imaging, communication, and energy harvesting. Nowadays, heterostructures have received significant attention to extend the performance of photodetectors, with exceptionally high optical absorption and a wide absorption range. However, the enhancement factors, exact mechanism, and facile fabrication procedures are long-standing problems. Here, a heterojunction of a two-dimensional chemical vapor deposition-grown monolayer of WSe 2 with a Cu 2 ZnSnS 4 (CZTS) film is introduced. The CZTS film as an abundant material was synthesized in the form of nanoparticles, and it showed a great effect on the enhancement of light absorption. By control of the gate voltage, the results of optoelectronic measurements reveal fast response (2.5 ms) and broadband photoresponsivity (∼550 A/W for 395−980 nm), which are about 2500 times higher than those of a conventional WSe 2 structure. The energy band structure at the interface of the heterojunction and simulated data with/without a gate voltage were used to investigate the device operation mechanism. It has been realized that the gate voltage has direct impacts on increasing the photocurrent and suppressing the recombination of the photocarriers. The observed experimental results and the proposed mechanism pave shortcuts to developing efficient photodetectors based on transition metal dichalcogenides and earth-abundant materials.

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Section: Introductionmentioning

confidence: 99%

Enhanced Broadband Photoresponsivity of the CZTS/WSe₂ Heterojunction by Gate Voltage

Ghods

Vardast

Esfandiar

et al. 2022

ACS Appl. Electron. Mater.

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“…Indeed, this is the dual gate structure, which can evaluate the dielectric constant of Er 2 O 3 on monolayer MoS 2 . [13,18,[32][33][34] The thicknesses of SiO 2 and Er 2 O 3 were determined by cross-sectional transmission electron microscopy (TEM) to be 95.3 and 5.3 nm, respectively, as shown in Figure 3c. To suppress the formation of an interface layer between Er 2 O 3 and the top gate electrode, the selection of material for the top gate electrode is essential.…”

Section: Demonstration Of the Top-gated Mos 2 Fet With A High-k Insul...mentioning

confidence: 99%

A Monolayer MoS₂ FET with an EOT of 1.1 nm Achieved by the Direct Formation of a High‐κ Er₂O₃ Insulator Through Thermal Evaporation

Uchiyama

Maruyama

Chen

et al. 2023

Small

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semiconductors, including Si and Ge, the mobility drastically degrades when the channel thickness of the conductor is below 5 nm due to thickness-fluctuationinduced scattering. [2] On the other hand, 2D materials maintain high mobility even under the monolayer limit (0.3-0.6 nm) [3][4][5] and exhibit inherently high on-current, as evidenced by the stronger quantummechanical effect that is observed. [6] In particular, transition metal dichalcogenides (TMDCs) are attractive materials for semiconductor channels of nanoscale FETs because of their high stability against oxidation [7] as well as their superior electrical properties, such as a large bandgap and relatively high carrier mobility. [3][4][5] Here, the large challenge with 2D-FET always involves the formation of highquality ultrathin high-κ oxide insulators. The atomic layer deposition (ALD) of dielectrics on TMDCs has a disadvantage in that high capacitive top gate stacks are formed on TMDCs because the nucleation of the oxide predominantly occurs at defect sites or through the physical adsorption of precursors onto the surface due to the absence of dangling bonds, [8] as shown in Figure 1a. Therefore, thick dielectrics are required to cover the whole surface without pinholes. [9] To form thin oxides with high dielectric constants by the ALD method, it is necessary to intentionally form nucleation sites on TMDCs. In fact, various surface modification methods, including surface treatment [10,11] and the formation of a buffer layer, [12][13][14][15][16][17][18] have been reported for oxide formation on TMDCs with high uniformity and dielectric properties. A surface treatment, including O 2 plasma [10] and ultraviolet ozone, [11] has improved the coverage and uniformity of ALD oxide on TMDCs; however, this treatment induces additional defects that produce extra scattering sites or dopants on TMDCs.The deposition of a buffer layer, including thin metal layers [12][13][14][15] and organic molecules, [16][17][18] is an effective method to provide nucleation sites without forming defects. To date, the thinnest equivalent oxide thickness (EOT) of 1 nm on monolayer TMDCs has been successfully reported by combining an organic monolayer of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) and ALD-HfO 2 for the top gate stack. [18] However, due to the quite low dielectric constant of PTCDA

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“…(d) Cross-sectional schematics of the evaporated top metal-contacted device and vdW metal-contacted device, demonstrating the corresponding characteristics of the gate voltage-leakage current with different gate dielectric thicknesses ranging from 2 to 6 nm. Reproduced with permission from ref . Copyright 2022 Springer GmbH.…”

Section: Characterization and Applications Of Vdw Metal Contactmentioning

confidence: 99%

“…As shown in Figure 19c, different VFET conduction mechanisms are clearly observed; the current conduction in the evaporated device is governed by the tunneling mechanism, whereas that in the vdW metalintegrated device is governed by the thermionic emission mechanism. Dang et al 82 reported vdW metal integrations on porous gate dielectrics in MoS 2 FET devices. The rich pinholes in the porous dielectric layer can be affected by the conventional evaporation process, resulting in the deterioration of the intrinsic dielectric property with an increase in the gate leakage current.…”

Section: Electronic Devicesmentioning

confidence: 99%

Van Der Waals Metal Contacts for Electronic and Optoelectronic Devices

Lee

Choi

2023

ACS Appl. Electron. Mater.

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For the fabrication of thin-film electronics, conventional physical vapor deposition (PVD) processes have been widely used to form metal contacts on various thin films. However, the PVD process, involving thermally activated high-energy metal atoms, damages the underlying thin films, severely deteriorating the performance and stability of the device. The van der Waals (vdW) metal-contact approach has recently emerged to avoid this issue. By transferring predeposited metal contacts using vdW interactions, atomically sharp and electronically clean heterointerfaces can be formed without generating unintended defects. In this article, we review the fundamentals, processes, and various applications of the vdW metal-integration approach. The classical theory of vdW interactions is first reviewed, followed by the introduction of various approaches for constructing vdW metal contacts on thin films. Subsequently, the influence of contact configuration on the performance of various applications is summarized. Finally, the remaining challenges and prospects are discussed for the practical usage and versatile application of vdW metal contacts for next-generation electronic devices.

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Ultimate dielectric scaling of 2D transistors via van der Waals metal integration

Cited by 22 publications

References 45 publications

Enhanced Broadband Photoresponsivity of the CZTS/WSe₂ Heterojunction by Gate Voltage

Enhanced Broadband Photoresponsivity of the CZTS/WSe₂ Heterojunction by Gate Voltage

A Monolayer MoS₂ FET with an EOT of 1.1 nm Achieved by the Direct Formation of a High‐κ Er₂O₃ Insulator Through Thermal Evaporation

Van Der Waals Metal Contacts for Electronic and Optoelectronic Devices

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Ultimate dielectric scaling of 2D transistors via van der Waals metal integration

Cited by 22 publications

References 45 publications

Enhanced Broadband Photoresponsivity of the CZTS/WSe2 Heterojunction by Gate Voltage

Enhanced Broadband Photoresponsivity of the CZTS/WSe2 Heterojunction by Gate Voltage

A Monolayer MoS2 FET with an EOT of 1.1 nm Achieved by the Direct Formation of a High‐κ Er2O3 Insulator Through Thermal Evaporation

Van Der Waals Metal Contacts for Electronic and Optoelectronic Devices

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Enhanced Broadband Photoresponsivity of the CZTS/WSe₂ Heterojunction by Gate Voltage

Enhanced Broadband Photoresponsivity of the CZTS/WSe₂ Heterojunction by Gate Voltage

A Monolayer MoS₂ FET with an EOT of 1.1 nm Achieved by the Direct Formation of a High‐κ Er₂O₃ Insulator Through Thermal Evaporation