Strain engineering in semiconducting two-dimensional crystals

Roldán, Rafael; Castellanos-Gómez, Andrés; Cappelluti, E.; Guinea, F.

doi:10.1088/0953-8984/27/31/313201

Cited by 457 publications

(458 citation statements)

References 173 publications

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“…This reversible modulation of the band gap could be used to make wavelength tunable phototransistors 16 , or MoS 2 strain sensors that have a sensitivity comparable to their state of the art silicon counterparts 20 . Moreover it has been suggested that strain could also improve the performance of MoS 2 transistors 21 , or could be used to create broadband light absorbers for energy harvesting 22 .The effect of strain on the band gap of 2D TMD's has been reported in a number of studies [9][10][11][12]20,23,24 , including uniaxial strains of up to ~4 % 25 and biaxial strains of up to ~3 % produced in highly localized sub-micron areas 26 . Band gap shifts in MoS 2 of ~300 meV have been induced by using very large hydrostatic pressures 27 , and tensile strain has induced shifts of as much as ~100 meV 11 .…”

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confidence: 99%

Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS₂

et al. 2016

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We demonstrate the continuous and reversible tuning of the optical band gap of suspended monolayer MoS 2 membranes by as much as 500 meV by applying very large biaxial strains. By using chemical vapor deposition (CVD) to grow crystals that are highly impermeable to gas, we are able to apply a pressure difference across suspended membranes to induce biaxial strains. We observe the effect of strain on the energy and intensity of the peaks in the photoluminescence (PL) spectrum, and find a linear tuning rate of the optical band gap of 99 meV/%. This method is then used to study the PL spectra of bilayer and trilayer devices under strain, and to find the shift rates and Grüneisen parameters of two Raman modes in monolayer MoS 2 . Finally, we use this result to show that we can apply biaxial strains as large as 5.6% across micron sized areas, and report evidence for the strain tuning of higher level optical transitions.KEYWORDS: Strain engineering, MoS 2 , photoluminescence, bandgap, Raman spectroscopy, biaxial strain 3 The ability to produce materials of truly nanoscale dimensions has revolutionized the potential for modulating or enhancing the physical properties of semiconductors by mechanical strain 1 . Strain engineering is routinely used in semiconductor manufacturing, with essential electrical components such as the silicon transistor or quantum well laser using strain to improve efficiency and performance 2,3 . Nano-structured materials are particularly suited to this technique, as they are often able to remain elastic when subject to strains many times larger than their bulk counterparts can withstand 4 . For instance, bulk silicon fractures when strained to just 1.2%, whereas silicon nanowires can reach strains of as much as 3.5% 5 . Parameters such as the band gap energy or carrier mobility of a semiconductor, which are often crucial to the electronic or photonic device performance, can be highly sensitive to the application of only small strains. The combination of this sensitivity with the ultra-high strains possible at the nanoscale could lead to an unprecedented ability to modify the electrical or photonic properties of materials in a continuous and reversible manner.Monolayer MoS 2, a 2D atomic crystal, has been shown in both theory 6,7 and experiment [8][9][10][11][12] to be an ideal candidate for strain engineering. It belongs to the class of 2D transition metal dichalcogonides (TMD's), and as a direct-gap semiconductor 13 has received significant interest as a channel material in transistors 14 , photovoltaics 15 and photodetection 16 devices. It has a breaking strain of 6-11% as measured by nanoindentation, which approaches its maximum theoretical strain limit 17 and classifies it as an ultra-strength material. Its electronic structure has also proven to be highly sensitive to strain, with experiments showing that the optical band gap reduces by ~50 meV/% for 4 uniaxial strain 8,11 , and is predicted to reduce by ~100 meV/% for biaxial strain 18,19 . This reversible modulation of the band...

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Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS₂

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“…the modification of a material's optical/electrical properties by means of mechanical stress. 16 This is in contrast to conventional 3D semiconductors that tend to break for moderate deformations. Very recent theoretical works explore the effect of strain on the band structure and optical properties of black phosphorus, predicting an even stronger response than in other 2D semiconductors such as transition metal dichalcogenides.…”

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Strong Modulation of Optical Properties in Black Phosphorus through Strain-Engineered Rippling

et al. 2016

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and (A.C-G.) andres.castellanos@imdea.org KEYWORDS. Black phosphorus, strain engineering, uniaxial strain, local strain, periodic deformation, quantum confinement, optical absorption. This is the post-peer reviewed version of the following article: J. Quereda et al. "Strong modulation of optical properties in black phosphorus through strain-engineered rippling" Nano Letters (2016) DOI:10.1021/acs.nanolett.5b04670 Which has been published in final form at: http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.5b04670 2 ABSTRACT Controlling the bandgap through local-strain engineering is an exciting avenue for tailoring optoelectronic materials. Two-dimensional crystals are particularly suited for this purpose because they can withstand unprecedented non-homogeneous deformations before rupture: one can literally bend them and fold them up almost like a piece of paper. Here, we study multi-layer black phosphorus sheets subjected to periodic stress to modulate their optoelectronic properties. We find a remarkable shift of the optical absorption band-edge of up to ~0.7 eV between the regions under tensile and compressive stress, greatly exceeding the strain tunability reported for transition metal dichalcogenides. This observation is supported by theoretical models which also predict that this periodic stress modulation can yield to quantum confinement of carriers at low temperatures. The possibility of generating large strain-induced variations in the local density of charge carriers opens the door for a variety of applications including photovoltaics, quantum optics and two-dimensional optoelectronic devices. TEXT.The recent isolation of black phosphorus has unleashed the interest of the community working on 2D materials because of its interesting electronic and optical properties: narrow intrinsic gap, ambipolar field effect and high carrier mobility. [1][2][3][4][5][6][7][8][9][10][11][12] Black phosphorus is composed of phosphorus atoms held together by strong bonds forming layers that interact through weak van der Waals forces holding the layers stacked on top of each other. This structure, without surface dangling This is the post-peer reviewed version of the following article: J. Quereda et al. "Strong modulation of optical properties in black phosphorus through strain-engineered rippling" Nano Letters (2016) DOI:10.1021/acs.nanolett.5b04670 Which has been published in final form at: http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.5b04670 3 bonds, allows black phosphorus susceptible to withstand very large localized deformations without breaking (similarly to graphene and MoS2). [13][14][15] Its outstanding mechanical resilience makes black phosphorus a prospective candidate for strain engineering, i.e. the modification of a material's optical/electrical properties by means of mechanical stress. 16 This is in contrast to conventional 3D semiconductors that tend to break for moderate deformations. Very recent theoretical works explore the effect of strain on the band structure and optical properties of black phosp...

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“…As a consequence, the electronic and optical properties of this material can be efficiently tuned by applying an external bias voltage [16][17][18][19][20] or by strain engineering. [21][22][23][24][25] In particular, it is possible to drive a semiconductor to semimetal transition, with the appearance of Dirac like dispersion. [16][17][18]26 In this paper we study the electronic spectrum of biased BP in the presence of a strong magnetic field.…”

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confidence: 99%

Quantum Hall effect and semiconductor-to-semimetal transition in biased black phosphorus

Yuan¹,

Veen²,

Katsnelson³

et al. 2016

Phys. Rev. B

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We study the quantum Hall effect of 2D electron gas in black phosphorus in the presence of perpendicular electric and magnetic fields. In the absence of a bias voltage, the external magnetic field leads to a quantization of the energy spectrum into equidistant Landau levels, with different cyclotron frequencies for the electron and hole bands. The applied voltage reduces the band gap, and eventually a semiconductor to semimetal transition takes place. This nontrivial phase is characterized by the emergence of a pair of Dirac points in the spectrum. As a consequence, the Landau levels are not equidistant anymore, but follow the εn ∝ √ nB characteristic of Dirac crystals as graphene. By using the Kubo-Bastin formula in the context of the kernel polynomial method, we compute the Hall conductivity of the system. We obtain a σxy ∝ 2n quantization of the Hall conductivity in the gapped phase (standard quantum Hall effect regime), and a σxy ∝ 4(n + 1/2) quantization in the semimetalic phase, characteristic of Dirac systems with non-trivial topology.

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Strain engineering in semiconducting two-dimensional crystals

Cited by 457 publications

References 173 publications

Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS₂

Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS₂

Strong Modulation of Optical Properties in Black Phosphorus through Strain-Engineered Rippling

Quantum Hall effect and semiconductor-to-semimetal transition in biased black phosphorus

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Strain engineering in semiconducting two-dimensional crystals

Cited by 457 publications

References 173 publications

Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2

Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2

Strong Modulation of Optical Properties in Black Phosphorus through Strain-Engineered Rippling

Quantum Hall effect and semiconductor-to-semimetal transition in biased black phosphorus

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Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS₂

Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS₂