Control of Schottky Barriers in Single Layer MoS<sub>2</sub> Transistors with Ferromagnetic Contacts

Chen, Jen-Ru; Odenthal, Patrick; Swartz, Adrian; Floyd, George Charles; Wen, Hua; Luo, Kelly Yunqiu; Kawakami, Roland

doi:10.1021/nl4010157

Cited by 356 publications

(373 citation statements)

References 25 publications

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“…13 The impact of the contact metal work function was studied in several materials. [14][15][16][17] In MoS 2 , for example, contact metals with diverse working functions ranging from 3.5 to 5.9 eV appear to all lie close to the conduction band, 14 thus suggesting Fermi level pinning by surface states. 18 The origin of this behavior needs to be understood before p-type devices can be made.…”

mentioning

confidence: 99%

Gate-modulated conductance of few-layer WSe2 field-effect transistors in the subgap regime: Schottky barrier transistor and subgap impurity states

Wang

Rhodes

Feng

et al. 2015

Applied Physics Letters

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Two key subjects stand out in the pursuit of semiconductor research: material quality and contact technology. The fledging field of atomically thin transition metal dichalcogenides (TMDCs) faces a number of challenges in both efforts. This work attempts to establish a connection between the two by examining the gate-dependent conductance of few-layer (1-5L) WSe2 field effect devices. Measurements and modeling of the subgap regime reveal Schottky barrier transistor behavior. We show that transmission through the contact barrier is dominated by thermionic field emission (TFE) at room temperature, despite the lack of intentional doping. The TFE process arises due to a large number of subgap impurity states, the presence of which also leads to high mobility edge carrier densities. The density of states of such impurity states is self-consistently determined to be approximately 1–2 × 1013/cm2/eV in our devices. We demonstrate that substrate is unlikely to be a major source of the impurity states and suspect that lattice defects within the material itself are primarily responsible. Our experiments provide key information to advance the quality and understanding of TMDC materials and electrical devices.

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mentioning

confidence: 99%

Gate-modulated conductance of few-layer WSe2 field-effect transistors in the subgap regime: Schottky barrier transistor and subgap impurity states

Wang

Rhodes

Feng

et al. 2015

Applied Physics Letters

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“…After repeated peeling from the thin film, it is ultimately stamped onto a SiO 2 /Si substrate and the tape is carefully removed. Significant amount of work has been done during the early stages of nanosheet preparation [151][152][153][154] . Lee et al 65 reported isolation of single-and few layered MoS 2 films from bulk crystals of 2H-MoS 2 (SPI, natural molybdenite) using the micromechanical exfoliation method widely adopted for preparation of graphene samples.…”

Section: Micromechanical Exfoliation Methodsmentioning

confidence: 99%

Emerging Energy Applications of Two-Dimensional Layered Materials

2015

Can Chem Trans

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Atomically thin semiconducting transition metal dichalcogenides (TMDCs) layered materials have recently been emerged as an exciting area of research due to accessibility for easy synthesis using various chemical and physical methods. These two-dimensional (2D) layered materials with single layer have direct and wide band gap due to which, they are more suitable for nanoelectronics and optoelectronics device applications. Here, we present a review of the energy related aspects of atomically thin layered materials like MoS 2 , WS 2 , MoSe 2 , WSe 2 , InSe, GaSe, GaTe, MoTe 2 , WTe 2 etc. for supercapacitor, solar cell, lithium ion battery and water splitting application. By significantly assessing various materials and comparing their performances with challenging technology, the advantages and disadvantages of this promising area of energy materials are recognized, which may provide guidelines for future progress.

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“…An important device merit is the TMR ratio and much theoretical and experimental efforts have been devoted to create MTJs with different ferromagnetic metals and insulating materials in order to generate a large ratio. While materials such as MgO and Al 2 O 3 are the most popular barrier materials in practical MTJs, 16-20 2D materials graphene 21,22 and transition-metal dichalcogenides 23,24 have also been investigated in this context.Given the huge interests in 2D nano-materials and the lack of knowledge about spin injection in MBP, in this work we investigate 2D MTJs consisting of a MBP as the tunnel barrier sandwiched by Ni contacts 25 based on a state-of-the-art theoretical approach where density functional theory (DFT) 26 is combined with the Keldysh nonequilibrium Green's function (NEGF) theory. 27 We are interested in understanding the nonequilibrium spin injection property of MBP driven by a finite external bias voltage.…”

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confidence: 99%

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confidence: 99%

Nonequilibrium spin injection in monolayer black phosphorus

Chen

Wang

et al. 2016

Phys. Chem. Chem. Phys.

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Monolayer black phosphorus (MBP) is an interesting emerging electronic material with a direct band gap and relatively high carrier mobility. In this work we report a theoretical investigation of nonequilibrium spin injection and spin-polarized quantum transport in MBP from ferromagnetic Ni contacts, in two-dimensional magnetic tunneling structures. We investigate physical properties of the spin injection efficiency, the tunnel magnetoresistance ratio, spin-polarized currents, charge currents and transmission coefficients as a function of external bias voltage, for two different device contact structures where MBP is contacted by Ni(111) and by Ni(100). While both structures are predicted to give respectable spin-polarized quantum transport, the Ni(100)/MBP/Ni(100) trilayer has the superior property where the spin injection and magnetoresistance ratio maintains almost a constant value against the bias voltage. The nonequilibrium quantum transport phenomenon is understood by analyzing the transmission spectrum at nonequilibrium. PACS numbers: 72.25.Mk, 73.43.Qt Two dimensional (2D) materials have received extensive investigations in recent years for possible applications in logic devices, photonic systems, solar cells, transparent substrates and perhaps most interestingly, flexible and wearable consumer electronics. 1 The thin layer of 2D material makes it a natural choice for producing flexible structures due to their out of plane flexibility. Many 2D materials have strong covalent bonds and diverse electronic structures -properties which are needed for reliable and durable applications.So far, several 2D materials have been fabricated successfully including the celebrated graphene, 2-5 various 2D transition-metal dichalcogenides, 6-8 and the monolayer black phosphorus (MBP). [9][10][11][12][13] In particular, as one of the newest members of 2D material family, MBP is very interesting in several aspects. First, different from transition-metal dichalcogenides, black phosphorus is made of a single atomic specie, phosphorus. Second, different from graphene, the phosphorus atoms in MBP are not all located in a plane but form a buckled hexagonal structure by covalence bonds and few-layer black phosphorus has an ideal direct bandgap, a property that is very important for optoelectronics. Third, MBP has an intrinsic band gap and graphene does not. Though lower than that of graphene, few-layer black phosphorus has respectable mobilities of ∼ 1000cm 2 V −1 s −1 as reported experimentally. 9 While the materials properties make MBP very interesting and potentially important for emerging flexible electronics, another critical issue is to achieve low power operation. In this regard, one notes that the energy scale of spin dynamics is typically many orders of magnitude smaller than that of charge dynamics, and low power electronics operation can thus be achieved in spintronics devices whose operation principle is based on spin dynamics. 14,15 Existing and well studied spintronic systems include magnetic random access memory...

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Control of Schottky Barriers in Single Layer MoS₂ Transistors with Ferromagnetic Contacts

Cited by 356 publications

References 25 publications

Gate-modulated conductance of few-layer WSe2 field-effect transistors in the subgap regime: Schottky barrier transistor and subgap impurity states

Gate-modulated conductance of few-layer WSe2 field-effect transistors in the subgap regime: Schottky barrier transistor and subgap impurity states

Emerging Energy Applications of Two-Dimensional Layered Materials

Nonequilibrium spin injection in monolayer black phosphorus

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Control of Schottky Barriers in Single Layer MoS2 Transistors with Ferromagnetic Contacts

Cited by 356 publications

References 25 publications

Gate-modulated conductance of few-layer WSe2 field-effect transistors in the subgap regime: Schottky barrier transistor and subgap impurity states

Gate-modulated conductance of few-layer WSe2 field-effect transistors in the subgap regime: Schottky barrier transistor and subgap impurity states

Emerging Energy Applications of Two-Dimensional Layered Materials

Nonequilibrium spin injection in monolayer black phosphorus

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Control of Schottky Barriers in Single Layer MoS₂ Transistors with Ferromagnetic Contacts