Pressure Induced Semiconductor-Semimetal Transition in WSe<sub>2</sub>

Liu, Bao; Han, Yonghao; Gao, Chunxiao; Ma, Yanzhang; Peng, Gang; Wu, Baojia; Liu, Cailong; Wang, Yue; Hu, Tingjing; Cui, Xiaoyan; Ren, Wanbin; Su, Ningning; Liu, Hongwu; Zou, Guangtian

doi:10.1021/jp104143e

Cited by 68 publications

(68 citation statements)

References 35 publications

(61 reference statements)

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“…We note that the c/a curve profile shows discontinuity at B19 GPa. Similar behaviour was also reported by Aksoy et al 50 and can be attributed to a pressure-induced structural distortion in which MoS 2 layers slide from the original 2H c -MoS 2 to the 2H a -MoS 2 structure 24 . Based on theoretical studies by Hromadová et al 22 , the peak positions in Raman measurements under high pressure coincide with the electronic properties of the emergent 2H a -MoS 2 phase.…”

Section: Discussionsupporting

confidence: 87%

“…The DAC technique coupled with a hydrostatic pressure medium (Fig. 1b) has been shown to be effective in elucidating the electrical, vibrational, optical and structural properties of a plethora of materials 21,[23][24][25] . The optically transparent window of the diamond allows us to conduct a series of in situ highpressure experiments including accurate pressure calibration from ruby fluorescence, electrical transport measurements and optical Raman and synchrotron X-ray diffraction (XRD) spectroscopy 26 , leading to the observation of S-M transition in multilayered MoS 2 at high pressures.…”

Section: Resultsmentioning

confidence: 99%

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Pressure-induced semiconducting to metallic transition in multilayered molybdenum disulphide

et al. 2014

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Molybdenum disulphide is a layered transition metal dichalcogenide that has recently raised considerable interest due to its unique semiconducting and opto-electronic properties. Although several theoretical studies have suggested an electronic phase transition in molybdenum disulphide, there has been a lack of experimental evidence. Here we report comprehensive studies on the pressure-dependent electronic, vibrational, optical and structural properties of multilayered molybdenum disulphide up to 35 GPa. Our experimental results reveal a structural lattice distortion followed by an electronic transition from a semiconducting to metallic state at B19 GPa, which is confirmed by ab initio calculations. The metallization arises from the overlap of the valance and conduction bands owing to sulphur-sulphur interactions as the interlayer spacing reduces. The electronic transition affords modulation of the opto-electronic gain in molybdenum disulphide. This pressuretuned behaviour can enable the development of novel devices with multiple phenomena involving the strong coupling of the mechanical, electrical and optical properties of layered nanomaterials.

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Section: Discussionsupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Pressure-induced semiconducting to metallic transition in multilayered molybdenum disulphide

et al. 2014

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“…As shown previously [27], the compressive hydrostatic pressure does not affect the electronic phase of TiS 2 . Therefore, we studied the effect of 2-8% uniform BTS on electronic structure of TiS 2 .…”

Section: Resultssupporting

confidence: 78%

Strain-induced electronic phase transition and strong enhancement of thermopower ofTiS2

2014

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Using first principles density functional theory calculations, we show a semimetal to semiconducting electronic phase transition for bulk TiS2 by applying uniform biaxial tensile strain. This electronic phase transition is triggered by charge transfer from Ti to S, which eventually reduces the overlap between Ti-(d) and S-(p) orbitals. The electronic transport calculations show a large anisotropy in electrical conductivity and thermopower, which is due to the difference in the effective masses along the in-plane and out of plane directions. Strain induced opening of band gap together with changes in dispersion of bands lead to three-fold enhancement in thermopower for both p-and n-type TiS2. We further demonstrate that the uniform tensile strain, which enhances the thermoelectric performance, can be achieved by doping TiS2 with larger iso-electronic elements such as Zr or Hf at Ti sites. [7]. Among the TMDs, TiS 2 has been in focus of extensive research due to its potential applications as cathode materials for lithium-ion batteries [8][9][10][11]. Previous experimental studies [12] have reported that nearly stoichiometric TiS 2 shows a large power factor value of 37.1 µW/K 2 -cm at room temperature that is comparable with the best thermoelectric material Bi 2 Te 3 [13]. The large power factor originates from a sharp increase in the density of states just above the Fermi energy as well as the inter-valley scattering of charge carriers [12,14,15]. However, the semimetallic nature of TiS 2 gives rise to bipolar effects which are not desirable for thermoelectric applications [16].The electronic structure of TiS 2 is very unique and even a slight change can significantly influence thermoelectric properties. It has been shown that 0.04% Mg doping at Ti-site in TiS 2 causes a 1.6 times increase in thermopower at 300 K [17]. Recently, it has been discovered that the electronic structures of semiconducting TMDs (MX 2 (M = Mo, W; X=S, Se, Te)) are very sensitive to the applied pressure/strain, which causes an electronic phase transition from semiconductor to metal [18][19][20][21]. Also few layers and mono-layer TMDs show wide range of tunability in electronic and magnetic properties by application of strain [22][23][24][25][26]. Contrary to that, TiS 2 remains semimetallic up to a compressive hydrostatic pressure of 20 GPa [27]. So far there has been no studies on effect of uniform tensile strain on the electronic properties of TiS 2 . Here, we carry out a study of the electronic structure of TiS 2 as a function of applied uniform biaxial tensile strain (BTS). The material undergoes electronic phase transition from semimetal to a small band gap (< 0.15 eV) semiconductor. Most interestingly, the semiconducting strained TiS 2 exhibits nearly a four-fold enhancement in thermopower compared to the unstrained phases. We also explore the possibility of generating such a strain by doping with larger atoms at Ti sites. Iso-electronic Hf and Zr turn out to be the best dopants to generate the 2% tensile strain producing the same...

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“…DPPH radical scavenging assay was done according to a published method [7]. Briefly, 2 mL of DPPH solution (0.2 mmol/L, in ethanol) was incubated with different concentrations of the sample.…”

Section: Dpph Radical Scavenging Assaymentioning

confidence: 99%

Characterization and DPPH Radical Scavenging Activity of Gallic Acid-Lecithin Complex

Liu¹,

Chen²,

Ma³

et al. 2014

Trop. J. Pharm Res

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Pressure Induced Semiconductor-Semimetal Transition in WSe₂

Cited by 68 publications

References 35 publications

Pressure-induced semiconducting to metallic transition in multilayered molybdenum disulphide

Pressure-induced semiconducting to metallic transition in multilayered molybdenum disulphide

Strain-induced electronic phase transition and strong enhancement of thermopower ofTiS2

Characterization and DPPH Radical Scavenging Activity of Gallic Acid-Lecithin Complex

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Pressure Induced Semiconductor-Semimetal Transition in WSe2

Cited by 68 publications

References 35 publications

Pressure-induced semiconducting to metallic transition in multilayered molybdenum disulphide

Pressure-induced semiconducting to metallic transition in multilayered molybdenum disulphide

Strain-induced electronic phase transition and strong enhancement of thermopower ofTiS2

Characterization and DPPH Radical Scavenging Activity of Gallic Acid-Lecithin Complex

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Pressure Induced Semiconductor-Semimetal Transition in WSe₂