Large and Tunable Photothermoelectric Effect in Single-Layer MoS<sub>2</sub>

Buscema, Michele; Barkelid, Maria; Zwiller, Val; Zant, Herre S. J. van der; Steele, Gary A.; Castellanos-Gómez, Andrés

doi:10.1021/nl303321g

Cited by 595 publications

(639 citation statements)

References 57 publications

(112 reference statements)

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“…Using temperature-dependent Raman spectroscopy on suspended sheets, Yan et al 32 extracted the thermal conductivity of single-layer MoS 2 (∼34.5 W/mK), which was found to be significantly lower than that of graphene. Buscema et al 33 measured the Seebeck coefficient in back-gated MoS 2 transistors and obtained a large tunable value, which could be varied between −4 × 10 2 μV/K and −1 × 10 5 μV/K by a gate voltage. This result shows that single-layer MoS 2 can be suitable for the aforementioned thermoelectric applications.…”

Section: ■ Thermal Propertiesmentioning

confidence: 99%

Single-Layer MoS₂ Electronics

2015

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CONSPECTUS: Atomic crystals of two-dimensional materials consisting of single sheets extracted from layered materials are gaining increasing attention. The most well-known material from this group is graphene, a single layer of graphite that can be extracted from the bulk material or grown on a suitable substrate. Its discovery has given rise to intense research effort culminating in the 2010 Nobel Prize in physics awarded to Andre Geim and Konstantin Novoselov. Graphene however represents only the proverbial tip of the iceberg, and increasing attention of researchers is now turning towards the veritable zoo of so-called "other 2D materials". They have properties complementary to graphene, which in its pristine form lacks a bandgap: MoS 2 , for example, is a semiconductor, while NbSe 2 is a superconductor. They could hold the key to important practical applications and new scientific discoveries in the two-dimensional limit. This family of materials has been studied since the 1960s, but most of the research focused on their tribological applications: MoS 2 is best known today as a high-performance dry lubricant for ultrahigh-vacuum applications and in car engines. The realization that single layers of MoS 2 and related materials could also be used in functional electronic devices where they could offer advantages compared with silicon or graphene created a renewed interest in these materials. MoS 2 is currently gaining the most attention because the material is easily available in the form of a mineral, molybdenite, but other 2D transition metal dichalcogenide (TMD) semiconductors are expected to have qualitatively similar properties. In this Account, we describe recent progress in the area of single-layer MoS 2 -based devices for electronic circuits. We will start with MoS 2 transistors, which showed for the first time that devices based on MoS 2 and related TMDs could have electrical properties on the same level as other, more established semiconducting materials. This allowed rapid progress in this area and was followed by demonstrations of basic digital circuits and transistors operating in the technologically relevant gigahertz range of frequencies, showing that the mobility of MoS 2 and TMD materials is sufficiently high to allow device operation at such high frequencies. Monolayer MoS 2 and other TMDs are also direct band gap semiconductors making them interesting for realizing optoelectronic devices. These range from simple phototransistors showing high sensitivity and low noise, to light emitting diodes and solar cells. All the electronic and optoelectronic properties of MoS 2 and TMDs are accompanied by interesting mechanical properties with monolayer MoS 2 being as stiff as steel and 30× stronger. This makes it especially interesting in the context of flexible electronics where it could combine the high degree of mechanical flexibility commonly associated with organic semiconductors with high levels of electrical performance. All these results show that MoS 2 and TMDs are promising materials for elect...

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Section: ■ Thermal Propertiesmentioning

confidence: 99%

Single-Layer MoS₂ Electronics

2015

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“…Single-layer MoS 2 (extracted from naturally occurring 2-H-phase material) has a direct electronic band gap ~1.8 eV [1,2] while bulk 2-H phase MoS 2 exhibits a lower indirect band gap ~ 1.3eV [3]. This semiconducting nature has been exploited to create MoS 2 field effect transistors (FETs) [4] with high on-off ratio and ultrasensitive photodetectors [5], amongst other optoelectronic and photonic [6,7] devices. The number of layers not only provides tunability of the band gap of MoS 2 for photonic applications [8], but also performance enhancements that may not be directly gap related.…”

Section: Introductionmentioning

confidence: 99%

Identifying different stacking sequences in few-layer CVD-grownMoS2by low-energy atomic-resolution scanning transmission electron microscopy

et al. 2016

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ABSTRACT:Atomically thin MoS 2 grown by chemical vapor deposition (CVD) is a promising candidate for the next-generation electronics due to inherent CVD scalability and controllability. However, it is well-known that the stacking sequence in few-layer MoS 2 can significantly impact the electrical and optical properties. Herein we report different intrinsic stacking sequences in CVD grown few-layer MoS 2 obtained by atomic-resolution annular-dark-field imaging in an aberration-corrected scanning transmission electron microscope operated at 50 keV. Tri-layer MoS 2 displays a new stacking sequence distinct from the commonly observed 2H and 3R phases of MoS 2 . Density functional theory is used to examine the stability of different stacking sequences, and the findings are consistent with our experimental observations.

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“…The research on multilayers of MoS 2 , among many other multilayers of TMDs, has been fueled by their novel properties intrinsic to two-dimensional materials. For example, successes of MoS 2 multilayers have been demonstrated for the purposes of energy-efficient field-effect transistor 9 , advanced electrocatalysts 10 , thermoelectric devices 11,12 with a large and tunable Seebeck coefficient, phototransistors 13 , superconductivity 14 , etc. MoS 2 is joining the ranks of other low-dimensional materials, demanding both efficient and accurate treatment of a first-principles approach [15][16][17][18] .…”

Section: Introductionmentioning

confidence: 99%

Direct calculation of the linear thermal expansion coefficients ofMoS2via symmetry-preserving deformations

Gan

Liu

2016

Phys. Rev. B

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Using density-functional perturbation theory and the Grüneisen formalism, we directly calculate the linear thermal expansion coefficients (TECs) of a hexagonal bulk system MoS2 in the crystallographic a and c directions. The TEC calculation depends critically on the evaluation of a temperature-dependent quantity Ii(T ), which is the integral of the product of heat capacity and Γi(ν), of frequency ν and strain type i, where Γi(ν) is the phonon density of states weighted by the Grüneisen parameters. We show that to determine the linear TECs we may use minimally two uniaxial strains in the z direction, and either the x or y direction. However, a uniaxial strain in either the x or y direction drastically reduces the symmetry of the crystal from a hexagonal one to a base-centered orthorhombic one. We propose to use an efficient and accurate symmetry-preserving biaxial strain in the xy plane to derive the same result for Γ(ν). We highlight that the Grüneisen parameter associated with a biaxial strain may not be the same as the average of Grüneisen parameters associated with two separate uniaxial strains in the x and y directions due to possible preservation of degeneracies of the phonon modes under a biaxial deformation. Large anisotropy of TECs is observed where the linear TEC in the c direction is about 1.8 times larger than that in the a or b direction at high temperatures. Our theoretical TEC results are compared with experiment. The symmetry-preserving approach adopted here may be applied to a broad class of two lattice-parameter systems such as hexagonal, trigonal, and tetragonal systems, which allows many complicated systems to be treated on a first-principles level.

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Large and Tunable Photothermoelectric Effect in Single-Layer MoS₂

Cited by 595 publications

References 57 publications

Single-Layer MoS₂ Electronics

Single-Layer MoS₂ Electronics

Identifying different stacking sequences in few-layer CVD-grownMoS2by low-energy atomic-resolution scanning transmission electron microscopy

Direct calculation of the linear thermal expansion coefficients ofMoS2via symmetry-preserving deformations

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Large and Tunable Photothermoelectric Effect in Single-Layer MoS2

Cited by 595 publications

References 57 publications

Single-Layer MoS2 Electronics

Single-Layer MoS2 Electronics

Identifying different stacking sequences in few-layer CVD-grownMoS2by low-energy atomic-resolution scanning transmission electron microscopy

Direct calculation of the linear thermal expansion coefficients ofMoS2via symmetry-preserving deformations

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Large and Tunable Photothermoelectric Effect in Single-Layer MoS₂

Single-Layer MoS₂ Electronics

Single-Layer MoS₂ Electronics