Formation of a Stable p–n Junction in a Liquid-Gated MoS2 Ambipolar Transistor

Zhang, Yijin; Ye, J. T.; Yomogida, Yohei; Takenobu, Taishi; Iwasa, Yoshihiro

doi:10.1021/nl400902v

Cited by 223 publications

(297 citation statements)

References 29 publications

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“…Interestingly, since ions are immobilized upon cooling through the glass transition, the conductance landscape in the channel established by VG and VDS above Tg will be frozen in space below Tg. This effect could have a strong impact on the transport characteristics, as recently reported in EDLTs fabricated on MoS2 and WSe2 flakes 29,47,48 . For the bias configuration in Fig.…”

Section: (A)mentioning

confidence: 51%

Direct Imaging of Nanoscale Conductance Evolution in Ion-Gel-Gated Oxide Transistors

Ren

Yuan

et al. 2015

Nano Lett.

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Electrostatic modification of functional materials by electrolytic gating has demonstrated a remarkably wide range of density modulation, a condition crucial for developing novel electronic phases in systems ranging from complex oxides to layered chalcogenides. Yet little is known microscopically when carriers are modulated in electrolyte-gated electric double-layer transistors (EDLTs) due to the technical challenge of imaging the buried electrolyte-semiconductor interface. Here, we demonstrate the real-space mapping of the channel conductance in ZnO EDLTs using a cryogenic microwave impedance microscope. A spin-coated ionic gel layer with typical thicknesses below 50 nm allows us to perform high resolution (on the order of 100 nm) sub-surface imaging, while maintaining the capability of inducing the metal-insulator transition under a gate bias.The microwave images vividly show the spatial evolution of channel conductance and its local fluctuations through the transition, as well as the uneven conductance distribution established by a large source-drain bias. The unique combination of ultra-thin ion-gel gating and microwave imaging offers a new opportunity to study the local transport and mesoscopic electronic properties in EDLTs.

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Section: (A)mentioning

confidence: 51%

Direct Imaging of Nanoscale Conductance Evolution in Ion-Gel-Gated Oxide Transistors

Ren

Yuan

et al. 2015

Nano Lett.

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“…29−32 In addition to FET operations, we have also demonstrated Schottky diode operations in our WSe 2 devices by applying asymmetric IL gate voltages to the two graphene/WSe 2 contacts. 33 Our Schottky diode device displays a significant rectifying behavior and a diode ideality factor of ∼1.3, signifying a high quality of the graphene/WSe 2 interface. Variable temperature electrical measurements performed on WSe 2 FETs with low-resistance graphene contacts reveal that as the temperature decreases from 160 to 77 K, the extrinsic field-effect mobility increases from ∼196 to ∼330 cm 2 V −1 s −1 for the electron channel and from ∼204 to ∼270 cm 2 V −1 s −1 for the hole channel.…”

mentioning

confidence: 83%

High Mobility WSe₂ p- and n-Type Field-Effect Transistors Contacted by Highly Doped Graphene for Low-Resistance Contacts

et al. 2014

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ABSTRACT:We report the fabrication of both n-type and p-type WSe 2 fieldeffect transistors with hexagonal boron nitride passivated channels and ionic-liquid (IL)-gated graphene contacts. Our transport measurements reveal intrinsic channel properties including a metal−insulator transition at a characteristic conductivity close to the quantum conductance e 2 /h, a high ON/OFF ratio of >10 7 at 170 K, and large electron and hole mobility of μ ≈ 200 cm 2 V −1 s −1 at 160 K. Decreasing the temperature to 77 K increases mobility of electrons to ∼330 cm 2 V −1 s −1 and that of holes to ∼270 cm 2 V −1 s −1 . We attribute our ability to observe the intrinsic, phonon-limited conduction in both the electron and hole channels to the drastic reduction of the Schottky barriers between the channel and the graphene contact electrodes using IL gating. We elucidate this process by studying a Schottky diode consisting of a single graphene/WSe 2 Schottky junction. Our results indicate the possibility to utilize chemically or electrostatically highly doped graphene for versatile, flexible, and transparent low-resistance ohmic contacts to a wide range of quasi-2D semiconductors. KEYWORDS: MoS 2 , WSe 2 , field-effect transistor, graphene, Schottky barrier, ionic-liquid gate L ayered transition metal dichalcogenides (TMDs) have recently emerged as promising materials for flexible electronics and optoelectronics applications. These systems have demonstrated many "graphene-like" properties including a relatively high carrier mobility, mechanical flexibility, chemical and thermal stability, and moreover offer the significant advantage of a substantial band gap. 1 Field-effect transistors (FETs) with atomically thin TMD channels are immune to short channel effects. 2 In addition, pristine surfaces of twodimensional (2D) TMDs are free of dangling bonds, which reduce surface roughness scattering and interface traps. Atomic layers of MoS 2 are probably the most extensively studied among the layered TMDs due to the availability of large natural molybdenite crystals from mining sources. 3 In addition to MoS 2 , several other semiconducting TMDs such as MoSe 2 , WS 2 , and WSe 2 with different band structures and charge neutrality levels may offer additional distinct properties. 1,4 However, the number of studies on TMDs other than MoS 2 is still small. 5−14 Among these studies, back-gated WSe 2 monolayer FETs with surface doping have already demonstrated a high field-effect mobility 8 reaching ∼140 cm 2 V −1 s −1 , which is substantially higher than most of the reported roomtemperature mobility values for MoS 2 . 15−19 A high intrinsic hole mobility of up to 500 cm 2 V −1 s −1 was also observed in bulk WSe 2 FETs. 11 Furthermore, WSe 2 is more resistant to oxidation in humid environments than MoS 2 . 10,20 A major challenge for developing WSe 2 -based electronic devices is that WSe 2 tends to form a substantial Schottky barrier (SB) with most metals commonly used for making electrical contacts. 8,13 This is a strong disadvantage, because lowre...

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“…Therefore considerable efforts are required for scalable synthesis of p-type MoS 2 film to realize practical applications. To date, a direct growth method of MoS 2 thin films by chemical vapor deposition (CVD) via vapor-phase reaction of MoO 3 and sulfur (S) powders, [18][19][20][21] MoCl 5 and S powders, 22,23 and metal Mo films [24][25][26][27][28] in a CVD furnace have been demonstrated to overcome a large area film synthesis. Among them, the direct grown method of TMDs (e.g.…”

mentioning

confidence: 99%

“…MoS 2 ) synthesis via sulfurization of transition metal films has great advantages for a large scale to have possibilities for the band gap engineering, 29 hetero-structures, 30 and doping. 25 Laskar et al 25 first reported on in situ p-type doping in cation-site by Nb diffusion in direct grown MoS 2 thin films. However, there are only a few reports for in situ p-type doping in anion-site using an acceptor dopant in film growth of MoS 2 .…”

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confidence: 99%

Phosphorous doped p-type MoS2 polycrystalline thin films via direct sulfurization of Mo film

et al. 2018

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We report on the successful synthesis of a p-type, substitutional doping at S-site, MoS2 thin film using Phosphorous (P) as the dopant. MoS2 thin films were directly sulfurized for molybdenum films by chemical vapor deposition technique. Undoped MoS2 film showed n-type behavior and P doped samples showed p-type behavior by Hall-effect measurements in a van der Pauw (vdP) configuration of 10×10 mm2 area samples and showed ohmic behavior between the silver paste contacts. The donor and the acceptor concentration were detected to be ∼2.6×1015 cm-3 and ∼1.0×1019 cm-3, respectively. Hall-effect mobility was 61.7 cm2V-1s-1 for undoped and varied in the range of 15.5 ∼ 0.5 cm2V-1s-1 with P supply rate. However, the performance of field-effect transistors (FETs) declined by double Schottky barrier contacts where the region between Ni electrodes on the source/drain contact and the MoS2 back-gate cannot be depleted and behaves as a 3D material when used in transistor geometry, resulting in poor on/off ratio. Nevertheless, the FETs exhibit hole transport and the field-effect mobility showed values as high as the Hall-effect mobility, 76 cm2V-1s-1 in undoped MoS2 with p-type behavior and 43 cm2V-1s-1 for MoS2:P. Our findings provide important insights into the doping constraints for transition metal dichalcogenides.

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Formation of a Stable p–n Junction in a Liquid-Gated MoS₂ Ambipolar Transistor

Cited by 223 publications

References 29 publications

Direct Imaging of Nanoscale Conductance Evolution in Ion-Gel-Gated Oxide Transistors

Direct Imaging of Nanoscale Conductance Evolution in Ion-Gel-Gated Oxide Transistors

High Mobility WSe₂ p- and n-Type Field-Effect Transistors Contacted by Highly Doped Graphene for Low-Resistance Contacts

Phosphorous doped p-type MoS2 polycrystalline thin films via direct sulfurization of Mo film

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Formation of a Stable p–n Junction in a Liquid-Gated MoS2 Ambipolar Transistor

Cited by 223 publications

References 29 publications

Direct Imaging of Nanoscale Conductance Evolution in Ion-Gel-Gated Oxide Transistors

Direct Imaging of Nanoscale Conductance Evolution in Ion-Gel-Gated Oxide Transistors

High Mobility WSe2 p- and n-Type Field-Effect Transistors Contacted by Highly Doped Graphene for Low-Resistance Contacts

Phosphorous doped p-type MoS2 polycrystalline thin films via direct sulfurization of Mo film

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Formation of a Stable p–n Junction in a Liquid-Gated MoS₂ Ambipolar Transistor

High Mobility WSe₂ p- and n-Type Field-Effect Transistors Contacted by Highly Doped Graphene for Low-Resistance Contacts