Experimental Determination of the Ionization Energies of MoSe2, WS2, and MoS2 on SiO2 Using Photoemission Electron Microscopy

Keyshar, Kunttal; Berg, Mark A.; Zhang, Xiang; Vajtai, Róbert; Gupta, Gautam; Chan, Catherine; Beechem, Thomas E.; Ajayan, Pulickel M.; Mohite, Aditya; Ohta, Taisuke

doi:10.1021/acsnano.7b03242

Cited by 76 publications

(82 citation statements)

References 60 publications

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“…In contrast, the WF of 1L‐WS 2 (5.34 eV) was larger than that of 3L‐WS 2 (5.26 eV). The measured WF values of MoS 2 and WS 2 are similar to those reported in the literature . In the case of MoS 2 , a similar thickness dependence of the WF has been reported …”

Section: Resultssupporting

confidence: 89%

Internal Fields in Multilayer WS₂/MoS₂ Heterostructures Epitaxially Grown on Sapphire Substrates

Kim

Tsai

et al. 2020

Physica Status Solidi (a)

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In conventional 3D heterostructures, a gradual potential gradient in constituent layers and an abrupt potential discontinuity at heterointerfaces can appear. Studies of the electrostatic potential in 2D heterostructures require careful characterizations and analyses because the 2D materials have distinct physical characteristics compared with their 3D counterparts. Herein, three kinds of samples are prepared using sulfurization of metal layers on single‐crystalline sapphire substrates: WS2, MoS2, and WS2/MoS2. The surface potential (VS) of the samples is measured using Kelvin probe force microscopy. The light‐induced VS change in the stand‐alone trilayer (3L‐) WS2 (−63 mV) is much more notable than that in the 3L‐WS2/3L‐MoS2 heterostructure (−12 mV). In contrast, the light‐induced VS change in the stand‐alone 3L‐MoS2 is positive and very large (≈200 mV). To explain these results, the potential and internal field distributions are proposed for both the stand‐alone (WS2 and MoS2) and heterostructure (WS2/MoS2) samples. The polarity and magnitude of the internal field depend on the electronic interaction and screening from neighboring 2D layers and underlying substrates. Relative peak shifts of the Raman spectra of the samples are obtained and discussed, with consideration of the internal field effects.

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Section: Resultssupporting

confidence: 89%

Internal Fields in Multilayer WS₂/MoS₂ Heterostructures Epitaxially Grown on Sapphire Substrates

Kim

Tsai

et al. 2020

Physica Status Solidi (a)

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“…The calculated positions of the VBM (−5.94 eV) and CBM (−4.08 eV) of MoS 2 agree well (within ±0.2 eV) with those reported in previous experimental and theoretical studies. [35][36][37] For MAPbI 3 nanosheets we find two very distinct values for the VBM, depending upon the surface termination. The MAIterminated surface gives a VBM of −4.54 eV, whereas a PbI 2 -terminated surface gives a value of −6.21 eV.…”

Section: Low-dimensional Perovskites Have Gained Increasing Attentionmentioning

confidence: 80%

Engineering the Phases and Heterostructures of Ultrathin Hybrid Perovskite Nanosheets

et al. 2020

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Low‐dimensional perovskites have gained increasing attention recently, and engineering their material phases, structural patterning and interfacial properties is crucial for future perovskite‐based applications. Here a phase and heterostructure engineering on ultrathin perovskites, through the reversible cation exchange of hybrid perovskites and efficient surface functionalization of low‐dimensional materials, is demonstrated. Using PbI2 as precursor and template, perovskite nanosheets of varying thickness and hexagonal shape on diverse substrates is obtained. Multiple phases, such as PbI2, MAPbI3 and FAPbI3, can be flexibly designed and transformed as a single nanosheet. A perovskite nanosheet can be patterned using masks made of 2D materials, fabricating lateral heterostructures of perovskite and PbI2. Perovskite‐based vertical heterostructures show strong interfacial coupling with 2D materials. As a demonstration, monolayer MoS2/MAPbI3 stacks give a type‐II heterojunction. The ability to combine the optically efficient perovskites with versatile 2D materials creates possibilities for new designs and functionalities.

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“…As one result, the characteristic Dirac cones of monolayer graphene are recovered in bilayer graphene on Ru, and the trilayer graphene on Ru behaves like free-standing bilayer graphene. SPE-LEEM-based μ-ARPES measurements are also employed to study the band alignment of TMDCs on SiO 2 [175,176], Au intercalation-induced doping in graphene [177], and Si intercalation/deintercalation of graphene on 6H-SiC (0001) [178].…”

Section: Electronic Structure Of Thin Filmsmentioning

confidence: 99%

Spectroscopic photoemission and low-energy electron microscopy studies of the surface and electronic structure of two-dimensional materials

Jin

Osgood

2019

Advances in Physics: X

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Advances in two-dimensional (2D) materials research have opened up new opportunities in miniaturization of optoelectronic and spintronic devices at the atomically thin limit. One major research thrust, which is the subject of this review, is the surface-and electronic structure of 2D materials and their van der Waals (vdW) heterostructures that may be significantly affected by the local atomic geometry and environment. As a result, there is a pressing need for powerful advanced microscopy and spectroscopy techniques for material characterization at a micro-or sub-micrometer lateral scale, which is a typical sample size in many 2D-materials experiments. Spectroscopic photoemission and low-energy electron microscopy (SPE-LEEM) offer a multifunctional approach that uniquely integrates microscopy, diffraction and spectroscopy techniques, enables real-time imaging and in situ structural, chemical and electronic analysis of surfaces and interfaces. This review covers the recent developments in SPE-LEEM investigations of surface-and electronic structure of 2D materials, and presents examples including exfoliated vdW layered materials, vdW heterostructures, and thin films synthesized by chemical vapor deposition and molecular beam epitaxy.

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Experimental Determination of the Ionization Energies of MoSe₂, WS₂, and MoS₂ on SiO₂ Using Photoemission Electron Microscopy

Cited by 76 publications

References 60 publications

Internal Fields in Multilayer WS₂/MoS₂ Heterostructures Epitaxially Grown on Sapphire Substrates

Internal Fields in Multilayer WS₂/MoS₂ Heterostructures Epitaxially Grown on Sapphire Substrates

Engineering the Phases and Heterostructures of Ultrathin Hybrid Perovskite Nanosheets

Spectroscopic photoemission and low-energy electron microscopy studies of the surface and electronic structure of two-dimensional materials

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Experimental Determination of the Ionization Energies of MoSe2, WS2, and MoS2 on SiO2 Using Photoemission Electron Microscopy

Cited by 76 publications

References 60 publications

Internal Fields in Multilayer WS2/MoS2 Heterostructures Epitaxially Grown on Sapphire Substrates

Internal Fields in Multilayer WS2/MoS2 Heterostructures Epitaxially Grown on Sapphire Substrates

Engineering the Phases and Heterostructures of Ultrathin Hybrid Perovskite Nanosheets

Spectroscopic photoemission and low-energy electron microscopy studies of the surface and electronic structure of two-dimensional materials

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Experimental Determination of the Ionization Energies of MoSe₂, WS₂, and MoS₂ on SiO₂ Using Photoemission Electron Microscopy

Internal Fields in Multilayer WS₂/MoS₂ Heterostructures Epitaxially Grown on Sapphire Substrates

Internal Fields in Multilayer WS₂/MoS₂ Heterostructures Epitaxially Grown on Sapphire Substrates