What Does Annealing Do to Metal–Graphene Contacts?

Leong, Wei Sun; Nai, Chang Tai; Thong, John T. L.

doi:10.1021/nl500999r

Cited by 114 publications

(127 citation statements)

References 25 publications

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“…In practice, closetoperfect interfaces require the removal or prevention of surface impurities (such as resist residues), as well as an annealing process. For example, in graphene, during annealing, the carbon atoms can dissolve into the contact metal (Ni or Co) and thus form strong covalent bonds, which contribute towards a much smaller contact resistance 44 . For multilayer TMDC SCs, only the top layer can be hybrid ized by metal top contacts, and thus only the vdW gap between the metal and the top layer of the TMDC is eliminated, as predicted by DFT 35,42 .…”

Section: Interface Geometrymentioning

confidence: 99%

Electrical contacts to two-dimensional semiconductors

et al. 2015

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Semiconducting electronic devices utilize fine control over the flow of charge carriers, which are injected into the semi conducting material through electrical contacts. The quality of the electrical contacts -quantified through contact resistance -is as important to the proper functioning of the entire device as the semiconductor (SC) itself. Since the early 1990s, researchers have explored a wide variety of electronic devices based on nanostruc tures with different dimensionalities, ranging from one dimensional (1D 20 and silicene 21 are also attracting growing interest. One of the most common electronic devices, in both the research and industrial environments, is the fieldeffect transistor (FET). Low contact resistance in 2D SCbased devices is critical for achiev ing high 'on' current, large photoresponse 22 and highfrequency operation 23 . However, the major issue for 2D SC FET transistors is the existence of a large contact resistance at the interface between the 2D SC and any bulk (or 3D) metal, which drastically restrains the drain current [24][25][26] . Contacting 2D SCs presents a certain number of experimental and conceptual challenges. The theoretical concepts that underlie our understanding of conventional metal-SC contacts break down in the limit where the SC thickness is smaller than the The performance of electronic and optoelectronic devices based on two-dimensional layered crystals, including graphene, semiconductors of the transition metal dichalcogenide family such as molybdenum disulphide (MoS 2 ) and tungsten diselenide (WSe 2 ), as well as other emerging two-dimensional semiconductors such as atomically thin black phosphorus, is significantly affected by the electrical contacts that connect these materials with external circuitry. Here, we present a comprehensive treatment of the physics of such interfaces at the contact region and discuss recent progress towards realizing optimal contacts for two-dimensional materials. We also discuss the requirements that must be fulfilled to realize efficient spin injection in transition metal dichalcogenides. depletion and transfer lengths. In the 2D limit, the properties of the interface -the chemical interaction between the metal and the SC -govern everything. Substitutional doping, a common strat egy adopted to decrease the contact resistance in bulk SCs, is not applicable here because it would modify both the 2D material and its properties. In addition, the pristine surface (that is, no dangling bonds) of a 2D material makes it difficult to form strong interface bonds with a metal, thereby increasing contact resistance.The quantum limit to the contact resistance (R C min ) is determined by the number of conducting modes within the SC channel 27,28 , which is connected to the 2D charge carrier density (n 2D ), yielding R C min = h/(2e 2 k F ) = 0.026/√n 2D ≈ 30 Ω μm at n 2D = 10 13 cm -2 (ref. 29) -a value three orders of magnitude below the typical contact resist ance to monolayer MoS 2 . Here, h is Planck's constant, k F is the Fermi wavevector a...

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Section: Interface Geometrymentioning

confidence: 99%

Electrical contacts to two-dimensional semiconductors

et al. 2015

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“…During metallization, covalent contacts are formed at the vacant sites, whereas top contacts are formed in the remaining areas. The phenomenon of carbon dissolution due to annealing was explained by Leong et al in their study on the effect of annealing on metal-graphene interfaces [45]. Annealing their Ni-contacted graphene device at 300 o C for 1 h showed a much higher Dband Raman intensity than just annealed graphene and Nicontacted graphene without anneal, which correlates to the carbon dissolution.…”

Section: Formation Of Covalent Contacts By Annealingmentioning

confidence: 90%

Approaches to Reduce the Contact Resistance by the Formation of Covalent Contacts in Graphene Thin Film Transistors

Han

Yeo

2017

Appl. Sci. Converg. Technol.

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Graphene, with a carrier mobility achieving up to 140,000 cm 2 /Vs at room temperature, makes it an ideal material for application in semiconductor devices. However, when the metal comes in contact with the graphene sheet, an energy barrier forms at the metal-graphene interface, resulting in a drastic reduction of the carrier mobility of graphene. In this review, the various methods of forming metal-graphene covalent contacts to lower the contact resistance are discussed. Furthermore, the graphene sheet in the area of metal contact can be cut in certain patterns, also discussed in this review, which provides a more efficient approach to forming covalent contacts, ultimately reducing the contact resistance for the realization of high-performance graphene devices.

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“…Both of the I-V of each lead are linear and the adjacent leads are electrically insulating before and after annealing. The decrease of resistance in G/SiC leads after annealing can be attributed to either desorption of species from the graphene surface or by a modified contact resistance between Au and G/SiC after the thermal annealing step [42]. Statistics Crystals 2017, 7, 378 3 of 11 on the resistivity of G/SiC leads before annealing show that the average resistivity of 11 leads is 11 kΩ/square.…”

Section: Characterization Of Graphene Electrodesmentioning

confidence: 99%

Thermal Stability of Epitaxial Graphene Electrodes for Conductive Polymer Nanofiber Devices

Kim

Lara‐Avila

et al. 2017

Crystals

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Abstract:We used large area, monolayer graphene epitaxially grown on SiC (0001) as contact electrodes for polymer nanofiber devices. Our fabrication process, which avoids polymer resist residues on the graphene surface, results in graphene-polyaniline nanofiber devices with Ohmic contacts and electrical conductivity comparable to that of Au-nanofiber devices. We further checked the thermal stability of the graphene contacts to polyaniline devices by annealing up to T = 800 • C, the temperature at which polyaniline nanofibers are carbonized but the graphene electrode remains intact. The thermal stability and Ohmic contact of polymer nanofibers are demonstrated here, which together with the chemical stability and atomic flatness of graphene, make epitaxial graphene on SiC an attractive contact material for future all-carbon electronic devices.

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What Does Annealing Do to Metal–Graphene Contacts?

Cited by 114 publications

References 25 publications

Electrical contacts to two-dimensional semiconductors

Electrical contacts to two-dimensional semiconductors

Approaches to Reduce the Contact Resistance by the Formation of Covalent Contacts in Graphene Thin Film Transistors

Thermal Stability of Epitaxial Graphene Electrodes for Conductive Polymer Nanofiber Devices

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