High-mobility field-effect transistors based on transition metal dichalcogenides

Podzorov, Vitaly; Gershenson, M. E.; Kloc, Ch.; Zeis, Roswitha; Bücher, E.

doi:10.1063/1.1723695

Cited by 521 publications

(432 citation statements)

References 20 publications

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“…Some of the first electrical measurements on semiconducting TMDs date back to the 1960s, when Fivaz and Moser showed that the carrier mobility of MoS 2 , MoSe 2 , and WSe 2 exceed 100 cm 2 /(V s) in the direction along the layers. 5 In 2004, the first transistors were fabricated on the surface of bulk WSe 2 crystals, 6 showing high mobility and ambipolar behavior. The room-temperature on/off ratio was however rather low (∼10) because of bulk conduction.…”

Section: ■ Introductionmentioning

confidence: 99%

Single-Layer MoS₂ Electronics

2015

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CONSPECTUS: Atomic crystals of two-dimensional materials consisting of single sheets extracted from layered materials are gaining increasing attention. The most well-known material from this group is graphene, a single layer of graphite that can be extracted from the bulk material or grown on a suitable substrate. Its discovery has given rise to intense research effort culminating in the 2010 Nobel Prize in physics awarded to Andre Geim and Konstantin Novoselov. Graphene however represents only the proverbial tip of the iceberg, and increasing attention of researchers is now turning towards the veritable zoo of so-called "other 2D materials". They have properties complementary to graphene, which in its pristine form lacks a bandgap: MoS 2 , for example, is a semiconductor, while NbSe 2 is a superconductor. They could hold the key to important practical applications and new scientific discoveries in the two-dimensional limit. This family of materials has been studied since the 1960s, but most of the research focused on their tribological applications: MoS 2 is best known today as a high-performance dry lubricant for ultrahigh-vacuum applications and in car engines. The realization that single layers of MoS 2 and related materials could also be used in functional electronic devices where they could offer advantages compared with silicon or graphene created a renewed interest in these materials. MoS 2 is currently gaining the most attention because the material is easily available in the form of a mineral, molybdenite, but other 2D transition metal dichalcogenide (TMD) semiconductors are expected to have qualitatively similar properties. In this Account, we describe recent progress in the area of single-layer MoS 2 -based devices for electronic circuits. We will start with MoS 2 transistors, which showed for the first time that devices based on MoS 2 and related TMDs could have electrical properties on the same level as other, more established semiconducting materials. This allowed rapid progress in this area and was followed by demonstrations of basic digital circuits and transistors operating in the technologically relevant gigahertz range of frequencies, showing that the mobility of MoS 2 and TMD materials is sufficiently high to allow device operation at such high frequencies. Monolayer MoS 2 and other TMDs are also direct band gap semiconductors making them interesting for realizing optoelectronic devices. These range from simple phototransistors showing high sensitivity and low noise, to light emitting diodes and solar cells. All the electronic and optoelectronic properties of MoS 2 and TMDs are accompanied by interesting mechanical properties with monolayer MoS 2 being as stiff as steel and 30× stronger. This makes it especially interesting in the context of flexible electronics where it could combine the high degree of mechanical flexibility commonly associated with organic semiconductors with high levels of electrical performance. All these results show that MoS 2 and TMDs are promising materials for elect...

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Section: ■ Introductionmentioning

confidence: 99%

Single-Layer MoS₂ Electronics

2015

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“…However, we cannot make an accurate estimate while neglecting the contact resistance. In a previous paper on a similar WSe 2 transistors, a similar material, a factor of 5 error due to neglecting the contact resistance was reported, 5 meaning that the value of 55 cm 2 /Vs could be an underestimate of the actual mobility in the device by a similar factor. From the Hall-effect measurements we also measure the capacitive coupling between the channel and the gate and find that the capacitive coupling can be increased by a factor of 3 following only the deposition of the top-gate dielectric and a factor of 50 for the floating gate/dielectric case.…”

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Reply to 'Measurement of mobility in dual-gated MoS2 transistors'

2013

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In our previous paper, 1 we report on switchable monolayer MoS 2 transistors with a high on-off ratio and we claim that dielectric screening can be used to increase the mobility of monolayer MoS 2 . We estimate its mobility using a method previously applied by Lemme et al. to top-gated graphene nanoribbons 2 , in which they extracted the channel mobility from the back-gating characteristic of the device, acquired with the top-gate disconnected. 2 It is a common practice to extract the field-effect effective mobility using, where L and W are channel length and width, C ch,gate is the capacitance between the channel and gate per unit area and V i the voltage drop across the channel. It is common practice to make two approximations here: contact resistance is neglected, (equivalent to assuming V i = V ds where V ds is the applied drain-source voltage, in practice, V i < V ds ) and C ch,gate is assumed to be equal to the geometric capacitance between the gate electrode and the channel. For accurate measurements, both the contact resistance and the charge density (or corresponding capacitance) need to be measured.Fuhrer and Hone suggest 3 that in our measurements, closely mirroring the approach previously used on top-gated graphene nanoribbons, 2 the back-gate and topgate capacitance are equal. If this is indeed the case, then for all the devices presented

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“…[1][2][3][4][5] However, fabrication of high-performance transistors of TMDs including WSe 2 , MoS 2 , and MoSe 2 has been a major challenge in 2D electronics. 6,7 The performance of current metal-contacted TMDs is limited by the presence of a significant Schottky barrier (SB) in most cases. [8][9][10][11]12 In silicon-based electronics, low-resistance ohmic contacts are achieved by selective ion implantation of drain/source regions below metal electrodes.…”

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confidence: 99%

“…Furthermore, the 1T phase MoS 2 is thermally unstable above 100 o C. The availability of a variety of semiconducting TMDs such as MoSe 2 , WS 2 and WSe 2 with different band structures and charge neutrality levels offers additional distinct properties and opportunities for device applications. 5,6,8,9,13,[26][27][28][29][30][31][32][33][34][35][36][37] However, the variation of electron affinity, band gap, and band alignments also presents significant challenges to contact engineering. To unlock the full potential of TMDs as channel materials for high-performance thin-film transistors, highly effective and versatile contact strategies for making low-resistance ohmic contacts are needed.…”

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confidence: 99%

Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe₂, MoS₂, and MoSe₂ Transistors

et al. 2016

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We report a new strategy for fabricating 2D/2D low-resistance ohmic contacts for a variety of transition metal dichalcogenides (TMDs) using van der Waals assembly of substitutionally doped TMDs as drain/source contacts and TMDs with no intentional doping as channel materials. We demonstrate that few-layer WSe 2 field-effect transistors (FETs) with 2D/2D contacts exhibit low contact resistances of ~ 0.3 kΩ µm, high on/off ratios up to > 10 9 , and high drive currents exceeding 320 µA µm -1 . These favorable characteristics are combined with a two-terminal field-effect hole mobility μ FE ≈ 2×10 2 cm 2 V -1 s -1 at room temperature, which increases to >2×10 3 cm 2 V -1 s -1 at cryogenic temperatures. We observe a similar performance also in MoS 2 and MoSe 2 FETs with 2D/2D drain and source contacts. The 2D/2D low-resistance ohmic contacts presented here represent a new device paradigm that overcomes a significant bottleneck in the performance of TMDs and a wide variety of other 2D materials as the channel materials in post-silicon electronics.

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High-mobility field-effect transistors based on transition metal dichalcogenides

Cited by 521 publications

References 20 publications

Single-Layer MoS₂ Electronics

Single-Layer MoS₂ Electronics

Reply to 'Measurement of mobility in dual-gated MoS2 transistors'

Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe₂, MoS₂, and MoSe₂ Transistors

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High-mobility field-effect transistors based on transition metal dichalcogenides

Cited by 521 publications

References 20 publications

Single-Layer MoS2 Electronics

Single-Layer MoS2 Electronics

Reply to 'Measurement of mobility in dual-gated MoS2 transistors'

Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe2, MoS2, and MoSe2 Transistors

Contact Info

Product

Resources

About

Single-Layer MoS₂ Electronics

Single-Layer MoS₂ Electronics

Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe₂, MoS₂, and MoSe₂ Transistors