Synthesis and Transfer of Single-Layer Transition Metal Disulfides on Diverse Surfaces

Lee, Yi Hsien; Yu, Lili; Wang, Han; Fang, Wenjing; Ling, Xi; Shi, Yumeng; Lin, C. T.; Huang, Jing; Chang, Mu Tung; Chang, Chia Seng; Dresselhaus, M. S.; Palacios, Tomás; Li, Lain‐Jong; Kong, Jing

doi:10.1021/nl400687n

Cited by 623 publications

(603 citation statements)

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“…Monolayer MoS 2 was synthesized by CVD, using solid sulphur (S) and molybdenum oxide (MoO 3 ) as the precursors and perylene-3,4,9,10-tetracarboxylic acid tetra-potassium salt (PTAS) 39 as the seed for the CVD growth (see Methods for details). Hall-bar devices were fabricated on these CVD MoS 2 monolayers.…”

Section: Resultsmentioning

confidence: 99%

Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition

et al. 2014

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Layered transition metal dichalcogenides display a wide range of attractive physical and chemical properties and are potentially important for various device applications. Here we report the electronic transport and device properties of monolayer molybdenum disulphide grown by chemical vapour deposition. We show that these devices have the potential to suppress short channel effects and have high critical breakdown electric field. However, our study reveals that the electronic properties of these devices are at present severely limited by the presence of a significant amount of band tail trapping states. Through capacitance and ac conductance measurements, we systematically quantify the density-of-states and response time of these states. Because of the large amount of trapped charges, the measured effective mobility also leads to a large underestimation of the true band mobility and the potential of the material. Continual engineering efforts on improving the sample quality are needed for its potential applications.

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Section: Resultsmentioning

confidence: 99%

Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition

et al. 2014

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“…The pump fluence was varied by a combination of a half-wave plate and polarizer, allowing us to tune the exciton excitation density. High-quality monolayers of MoS 2 were CVD-grown on a sapphire substrate 38,39 and mounted inside a cold-finger cryostat with temperature of 10 K for all measurements in this study.…”

Section: Discussionmentioning

confidence: 99%

Intervalley biexcitons and many-body effects in monolayerMoS2

et al. 2015

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Interactions between two excitons can result in the formation of bound quasiparticles, known as biexcitons. Their properties are determined by the constituent excitons, with orbital and spin states resembling those of atoms. Monolayer transition metal dichalcogenides (TMDs) present a unique system where excitons acquire a new degree of freedom, the valley pseudospin, from which a novel intervalley biexciton can be created. These biexcitons comprise two excitons from different valleys, which are distinct from biexcitons in conventional semiconductors and have no direct analogue in atomic and molecular systems. However, their valley properties are not accessible to traditional transport and optical measurements. Here, we report the observation of intervalley biexcitons in the monolayer TMD MoS2 using ultrafast pump-probe spectroscopy. By applying broadband probe pulses with different helicities, we identify two species of intervalley biexcitons with large binding energies of 60 meV and 40 meV. In addition, we also reveal effects beyond biexcitonic pairwise interactions in which the exciton energy redshifts at increasing exciton densities, indicating the presence of many-body interactions among them.

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“…The sample consists of high-quality monolayers of WS 2 that were grown on sapphire substrates by chemical vapor deposition (CVD) [10,11]. All measurements in this study were conducted at ambient condition (300 K, 1 atm).…”

Section: Experimental Methodsmentioning

confidence: 99%

“…These materials are layered in structure, from which we can isolate a monolayer of TMDs through mechanical exfoliation or chemical vapor deposition (CVD) growth method [10,11]. Monolayer TMDs have a lattice structure similar to graphene but, unlike graphene, these materials possess a semiconducting gap between 1-2 eV.…”

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Coherent Light-Matter Interactions in Monolayer Transition-Metal Dichalcogenides

Sie

2018

Springer Theses

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Semiconductors that are thinned down to a few atomic layers can exhibit novel properties beyond those encountered in bulk forms. Transition-metal dichalcogenides (TMDs) such as MoS 2 , WS 2 and WSe 2 are prime examples of such semiconductors. They appear in layered structure that can be reduced to a stable single layer where remarkable electronic properties can emerge. Monolayer TMDs have a pair of electronic valleys which have been proposed as a new way to carry information in next generation devices, called valleytronics. However, these valleys are normally locked in the same energy level, which limits their potential use for applications.This dissertation presents the optical methods to split their energy levels by means of coherent light-matter interactions. Experiments were performed in a pump-probe technique using a transient absorption spectroscopy on MoS 2 and WS 2 , and a newly developed XUV light source for time and angle-resolved photoemission spectroscopy (TR-ARPES) on WSe 2 and WTe 2 . Hybridizing the electronic valleys with light allows us to optically tune their energy levels in a controllable valley-selective manner. In particular, by using off-resonance circularly polarized light at small detuning, we can tune the energy level of one valley through the optical Stark effect. At larger detuning, we observe a separate contribution from the so-called Bloch-Siegert effect, a delicate phenomenon that has eluded direct observation in solids. The two effects obey opposite selection rules, which enables us to separate the two effects at two different valleys.Monolayer TMDs also possess strong Coulomb interaction that enhances many-body interactions between excitons, both bonding and non-bonding interactions. In the former, bound excitonic quasiparticles such as biexcitons play a unique role in coherent light-matter interactions where they couple the two valleys to induce opposite energy shifts. In the latter, non-bonding interactions between excitons are found to exhibit energy shifts that effectively mimics the Lennard-Jones interactions between atoms. Through these works, we demonstrate new methods to optically tune the energy levels of electronic valleys in monolayer TMDs. AcknowledgmentsFirst and foremost, I would like to thank my advisor Prof. Nuh Gedik for his mentorship and support. He has been a constant source of inspiration since I first started my graduate studies. Actually it was even before that. I remember my first meeting at a conference in Boston where he presented a real-time image of crystalline lattice motion. The idea of watching Michael Jackson performing Billie Jean flashed through my head, because he was that cool and inspiring, and he continues to be so. He has been a tremendous support since day one, where I was given the opportunity to design and build the XUV beamline for ARPES in the lab as well as the freedom to build the white-light setup next to it. His vigor to make new innovations in timeresolved experiments is always inspiring. Throughout my graduate studies, he...

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Synthesis and Transfer of Single-Layer Transition Metal Disulfides on Diverse Surfaces

Cited by 623 publications

References 33 publications

Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition

Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition

Intervalley biexcitons and many-body effects in monolayerMoS2

Coherent Light-Matter Interactions in Monolayer Transition-Metal Dichalcogenides

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