Exfoliation of 2D van der Waals crystals in ultrahigh vacuum for interface engineering

Sun, Zhenyu; Han, Xu; Cai, Zhihao; Yue, Shaosheng; Geng, Daiyu; Rong, Dongke; Zhao, Lin; Zhang, Yi‐Qi; Cheng, Peng; Chen, Lan; Zhou, Xianju; Huang, Yuan; Wu, Kehui; Feng, Baojie

doi:10.1016/j.scib.2022.05.017

Cited by 12 publications

(19 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The magnetic electron gas on the surface of the nonmagnetic bulk is an unexpected finding for the electride Hf 2 S. In real materials, the cleaved Hf 2 S surface often exhibits the amorphous structure, 20 which is also consistent with the large exfoliation energy from our calculation (279.1 meV/Å 2 ). To observe such magnetic surface electron gas, one could obtain a flat and clean surface of Hf 2 S by using the molecular beam epitaxy (MBE) growth technique 37 or cleaving the bulk material in an ultra-highvacuum environment.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Magnetic Surface on Nonmagnetic Bulk of Electride Hf₂S

Zhang

Qiu

et al. 2022

J. Phys. Chem. C

View full text Add to dashboard Cite

A recent experiment has reported the self-passivated electride Hf 2 S with excellent stability and continuous electrocatalytic ability [S. H. Kang et al., Sci. Adv. 2020, 6, eaba7416]. Starting from its 2H-type layered structure, we have studied the electronic, magnetic, and transport properties of the electride Hf 2 S in the monolayer and multilayer forms by combining first-principles electronic structure calculations and Kubo formula approach. Our calculations indicate that these thin films of Hf 2 S electride are both dynamically and thermodynamically stable. Astonishingly, the calculations further show that the outmost Hf atoms and the surface electron gas of the Hf 2 S multilayers are spin polarized, while the inner Hf atoms and the electron gas in the interlayer regions remain nonmagnetic. Due to the magnetic surface, the multilayer Hf 2 S exhibits many unusual transport properties such as the surface anomalous Hall effect and the electric-field-induced layer Hall effect. Our theoretical predictions on Hf 2 S call for future experimental verification.

show abstract

Section: ■ Results and Discussionmentioning

confidence: 99%

Magnetic Surface on Nonmagnetic Bulk of Electride Hf₂S

Zhang

Qiu

et al. 2022

J. Phys. Chem. C

View full text Add to dashboard Cite

show abstract

“…Additionally, Raman and x-ray photoelectron spectroscopy (XPS) helped identify humidity, rather than O 2 or N 2 , as the main cause of surface aging, which was shown to be reversible by UHV annealing at 600 K for 2-3 hours and preventable by covering the surface with a protective polymer layer. In another study, Raman and PL spectroscopy of UHV-exfoliated TMDCs on various substrates showed that the interaction with noble metals Au and Ag is stronger than with base metals Fe and Cr [64]. These authors also exfoliated smaller (10 µm) MoS 2 and phosphorene flakes on Au, several days after the metal deposition in UHV.…”

Section: Exfoliation On Non-au Metalsmentioning

confidence: 94%

“…The cleanliness of the 2D material/Au interface has been identified as one of the most important factors for large monolayer yield. The exfoliation proceeds best on freshly grown Au surface and gradually ceases to work after 10-20 min of exposure to air (and longer in vacuum) [30,64]. This is likely due to the airborne contaminants, which build up on the surface and weaken adhesion between the 2D monolayer and the metal [30,65].…”

Section: Key Factors Affecting the Exfoliationmentioning

confidence: 99%

“…The typical partial pressures of oxygen are around 10 2 mbar in air, 10 −5 mbar in a glovebox, and <10 −10 mbar in UHV. Depending on the rate of oxidation for a particular metal, the typical time windows for successful exfoliation are impractically short in air [63], but could be as long as seconds/minutes in a glovebox [52] or hours/days under UHV [64]. The strong interaction between MoS 2 and Ag synthesized under UHV using a pulsed laser deposition was shown to weaken upon formation of substoichiometric molybdenum oxysulfide after the exposure to air [68].…”

Section: Exfoliation On Non-au Metalsmentioning

confidence: 99%

“…Another recent UHV exfoliation study succeeded in preparing > 100 µm-sized TMDCs on Au, Ag, and Ge, and found that, surprisingly, the Ag substrate yielded somewhat larger flakes than Au [56]. The air-induced degradation has also been suppressed by encapsulating samples with poly(methyl methacrylate) [64,68].…”

Section: Exfoliation On Non-au Metalsmentioning

confidence: 99%

See 2 more Smart Citations

When 2D materials meet metals

Pirker,

Honolka,

Velický

et al. 2024

2D Mater.

View full text Add to dashboard Cite

This review delves into the intricacies of the interfaces formed between two-dimensional (2D) materials and metals, exploring a realm rich with fundamental insights and promising applications. Historically, our understanding of 2D materials emanated from studies employing dielectric substrates or suspended samples. However, integrating metals in the exfoliation and growth processes of 2D materials has opened up new avenues, unveiling various shades of interactions ranging from dispersive forces to covalent bonding.The resulting modifications in 2D materials, particularly transition metal dichalcogenides (TMDCs), offer more than a theoretical intrigue. They bear substantial implications for (opto)electronics, altering Schottky barrier heights and contact resistances in devices. We explore metal-mediated methods for TMDC exfoliation, elucidating the mechanisms and their impact on TMDC-metal interactions. Delving deeper, we scrutinize the fundamentals of these interactions, focusing primarily on MoS2 and Au.Despite the recent surge of interest and extensive studies, critical gaps remain in our understanding of these intricate interfaces. We discuss controversies, such as the changes in Raman or photoemission signatures of MoS2 on Au, and propose potential explanations. The interplay between charge redistribution, substrate-induced bond length variations, and interface charge transfer processes are examined. Finally, we address the intriguing prospect of TMDC phase transitions induced by strongly interacting substrates and their implications for contact design.

show abstract

Gold‐Template‐Assisted Mechanical Exfoliation of Large‐Area 2D Layers Enables Efficient and Precise Construction of Moiré Superlattices

Wu,

Wang,

Yang

et al. 2024

Advanced Materials

Self Cite

View full text Add to dashboard Cite

Moiré superlattices, consisting of rotationally aligned 2D atomically thin layers, provide a highly novel platform for the study of correlated quantum phenomena. However, reliable and efficient construction of moiré superlattices is challenging because of difficulties to accurately angle‐align small exfoliated 2D layers and the need to shun wet‐transfer processes. Here, we demonstrate efficient and precise construction of various moiré superlattices by picking up and stacking large‐area 2D mono‐ or few‐layer crystals with predetermined crystal axes, made possible by a gold‐template‐assisted mechanical exfoliation method. The exfoliated 2D layers are semiconductors, superconductors, or magnets and their high quality is confirmed by photoluminescence and Raman spectra and by electrical transport measurements of fabricated field‐effect transistors and Hall devices. Twisted homobilayers with angle‐twisting accuracy of ∼0.3 degrees, twisted heterobilayers with sub‐degree angle‐alignment accuracy, and multilayer superlattices have been precisely constructed and characterized by their moiré patterns, interlayer excitons, and second harmonic generation. The present study paves the way for exploring emergent phenomena in moiré superlattices.This article is protected by copyright. All rights reserved

show abstract

Exfoliation of 2D van der Waals crystals in ultrahigh vacuum for interface engineering

Cited by 12 publications

References 43 publications

Magnetic Surface on Nonmagnetic Bulk of Electride Hf₂S

Magnetic Surface on Nonmagnetic Bulk of Electride Hf₂S

When 2D materials meet metals

Gold‐Template‐Assisted Mechanical Exfoliation of Large‐Area 2D Layers Enables Efficient and Precise Construction of Moiré Superlattices

Contact Info

Product

Resources

About

Exfoliation of 2D van der Waals crystals in ultrahigh vacuum for interface engineering

Cited by 12 publications

References 43 publications

Magnetic Surface on Nonmagnetic Bulk of Electride Hf2S

Magnetic Surface on Nonmagnetic Bulk of Electride Hf2S

When 2D materials meet metals

Gold‐Template‐Assisted Mechanical Exfoliation of Large‐Area 2D Layers Enables Efficient and Precise Construction of Moiré Superlattices

Contact Info

Product

Resources

About

Magnetic Surface on Nonmagnetic Bulk of Electride Hf₂S

Magnetic Surface on Nonmagnetic Bulk of Electride Hf₂S