Characterization of metal contacts for two-dimensional MoS2 nanoflakes

Walia, Sumeet; Balendhran, Sivacarendran; Wang, Yichao; Kadir, Rosmalini Ab; Zoolfakar, Ahmad Sabirin; Atkin, Paul; Ou, Jian Zhen; Sriram, Sharath; Kalantar‐zadeh, Kourosh; Bhaskaran, Madhu

doi:10.1063/1.4840317

Cited by 145 publications

(105 citation statements)

References 15 publications

Supporting

Mentioning

103

Contrasting

Unclassified

Order By: Relevance

“…W, Au, Pd, and Ni, and that would be expected to form a high electron Schottky barrier with MoS 2 . [12][13][14][15][16][17][18][19][20] In another study, 21 the conductivity polarity measured on gold nanoparticles deposited on MoS 2 using I-V and Raman measurements also showed substantial inconsistencies. In that study, the n-and p-type behavior was measured on samples that were prepared in an identical manner and the variability was explained by the difference in MoS 2 thickness and/or by the Au-MoS 2 interface interaction.…”

mentioning

confidence: 93%

Impurities and Electronic Property Variations of Natural MoS₂Crystal Surfaces

et al. 2015

View full text Add to dashboard Cite

Room temperature X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICPMS), high resolution Rutherford backscattering spectrometry (HR-RBS), Kelvin probe method, and scanning tunneling microscopy (STM) are employed to study the properties of a freshly exfoliated surface of geological MoS2 crystals. Our findings reveal that the semiconductor 2H-MoS2 exhibits both n- and p-type behavior, and the work function as measured by the Kelvin probe is found to vary from 4.4 to 5.3 eV. The presence of impurities in parts-per-million (ppm) and a surface defect density of up to 8% of the total area could explain the variation of the Fermi level position. High resolution RBS data also show a large variation in the MoSx composition (1.8 < x < 2.05) at the surface. Thus, the variation in the conductivity, the work function, and stoichiometry across small areas of MoS2 will have to be controlled during crystal growth in order to provide high quality uniform materials for future device fabrication.

show abstract

mentioning

confidence: 93%

Impurities and Electronic Property Variations of Natural MoS₂Crystal Surfaces

et al. 2015

View full text Add to dashboard Cite

show abstract

“…[10][11] Recently, efforts were made to improve the device performance through understanding the influence of contact electrode, limitations in carrier transport and effect of different substrate on charge carrier mobility. [8][9][12][13][14][15][16][17][18][19] Analysis of the literature reveals that, variations in mobility values may came from the schottky barriers (SBs) at metal/semiconductor interfaces and differences in fabrication process. In order to overcome the schottky barrier problem, different strategies have been used.…”

Section: Introductionmentioning

confidence: 99%

Highly Stable and Tunable Chemical Doping of Multilayer WS₂ Field Effect Transistor: Reduction in Contact Resistance

Khalil

Khan

Eom

et al. 2015

ACS Appl. Mater. Interfaces

134

View full text Add to dashboard Cite

The development of low resistance contacts to 2D transition-metal dichalcogenides (TMDs) is still a big challenge for the future generation field effect transistors (FETs) and optoelectronic devices. Here, we report a chemical doping technique to achieve low contact resistance by keeping the intrinsic properties of few layers WS2. The transfer length method has been used to investigate the effect of chemical doping on contact resistance. After doping, the contact resistance (Rc) of multilayer (ML) WS2 has been reduced to 0.9 kΩ·μm. The significant reduction of the Rc is mainly due to the high electron doping density, thus a reduction in Schottky barrier height, which limits the device performance. The threshold voltage of ML-WS2 FETs confirms a negative shift upon the chemical doping, as further confirmed from the positions of E(1)2g and A1g peaks in Raman spectra. The n-doped samples possess a high drain current of 65 μA/μm, with an on/off ratio of 1.05 × 10(6) and a field effect mobility of 34.7 cm(2)/(V·s) at room temperature. Furthermore, the photoelectric properties of doped WS2 flakes were also measured under deep ultraviolet light. The potential of using LiF doping in contact engineering of TMDs opens new ways to improve the device performance.

show abstract

“…The tunnel barrier height in Gr/TMD/metal heterostructure is determined by the band offset at graphene/TMD interface (Φ GT ) and metal/TMD interface (Φ MT ) [24]. If the Schottky-Mott rule is assumed to hold, then these band offsets can be expressed as Φ = φ − χ, where φ denote work function of the metal or graphene, χ the electron affinity of the TMD [25]. Recent density functional theory calculations have shown the electron affinity of WS 2 to be χ ~ 4.0 eV [22]; and so considering the fact that the work function of graphene, Ti, and …”

Section: (D) and (E) Note That Althoughmentioning

confidence: 99%

Tunneling transport in a few monolayer-thick WS2/graphene heterojunction

Yamaguchi

Moriya

Inoue

et al. 2014

Applied Physics Letters

View full text Add to dashboard Cite

This paper demonstrates the high-quality tunnel barrier characteristics and layer number controlled tunnel resistance of a transition metal dichalcogenide (TMD) measuring just a few monolayers in thickness. Investigation of vertical transport in WS 2 and MoS 2 TMDs in graphene/TMD/metal heterostructures revealed that WS 2 exhibits tunnel barrier characteristics when its thickness is between 2 to 5 monolayers, whereas MoS 2 experiences a transition from tunneling to thermionic emission transport with increasing thickness within the same range. Tunnel resistance in a graphene/WS 2 /metal heterostructure therefore increases exponentially with the number of WS 2 layers, revealing the tunnel barrier height of WS 2 to be 0.37 eV. a)

show abstract

Characterization of metal contacts for two-dimensional MoS2 nanoflakes

Cited by 145 publications

References 15 publications

Impurities and Electronic Property Variations of Natural MoS₂Crystal Surfaces

Impurities and Electronic Property Variations of Natural MoS₂Crystal Surfaces

Highly Stable and Tunable Chemical Doping of Multilayer WS₂ Field Effect Transistor: Reduction in Contact Resistance

Tunneling transport in a few monolayer-thick WS2/graphene heterojunction

Contact Info

Product

Resources

About

Characterization of metal contacts for two-dimensional MoS2 nanoflakes

Cited by 145 publications

References 15 publications

Impurities and Electronic Property Variations of Natural MoS2Crystal Surfaces

Impurities and Electronic Property Variations of Natural MoS2Crystal Surfaces

Highly Stable and Tunable Chemical Doping of Multilayer WS2 Field Effect Transistor: Reduction in Contact Resistance

Tunneling transport in a few monolayer-thick WS2/graphene heterojunction

Contact Info

Product

Resources

About

Impurities and Electronic Property Variations of Natural MoS₂Crystal Surfaces

Impurities and Electronic Property Variations of Natural MoS₂Crystal Surfaces

Highly Stable and Tunable Chemical Doping of Multilayer WS₂ Field Effect Transistor: Reduction in Contact Resistance