Tunable Band Gap Photoluminescence from Atomically Thin Transition-Metal Dichalcogenide Alloys

Chen, Yanfeng; Xi, Jinyang; Dumcenco, Dumitru; Liu, Zheng; Suenaga, Kazu; Wang, Dong; Shuai, Zhigang; Huang, Y. S.; Xie, Liming

doi:10.1021/nn401420h

Cited by 565 publications

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“…Although the differences in the Raman spectra for Nb and Mo doping were small, we observed significant changes in the PL spectra for Nb-doped samples, which has never been observed for Mo doping in monolayer WS 2 . 15,24,28) As seen in Fig. 3(a), undoped WS 2 monolayers have a PL peak at 1.98 eV, and the peak originates from the emission of free neutral and charged excitons.…”

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“…As an impurity, Mo atoms are well studied and cause bandgap narrowing through the substitution of W sites in monolayer WS 2 . 14,15,23,24) However, there are very few studies on the doping of other transition metals for monolayer TMDCs. In the present study, Nb is selected because its atomic size is comparable to that of Mo and it is reported to generate acceptor states for some TMDCs.…”

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confidence: 99%

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Growth and optical properties of Nb-doped WS₂ monolayers

Sasaki

Kobayashi

Liu³

et al. 2016

Appl. Phys. Express

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We report the chemical vapor deposition growth of Nb-doped WS 2 monolayers and their characterization. Electron microscopy observations reveal that the Nb atom was substituted at the W site at a rate of approximately 0.5%. Unlike Mo doping, Nb-doped samples have photoluminescence (PL) peaks at 1.4-1.6 eV at room temperature. The peak energies are lower than the optical bandgap of 1.8 eV, and a saturation behavior of PL intensity is observed with the increase in excitation power. These results indicate that the observed PL peaks are assignable to the emission from impurity states generated by the substitution of Nb. © 2016 The Japan Society of Applied Physics T he optical properties of atomic-layer transition metal dichalcogenides (TMDCs) have recently attracted much attention owing to their wide-range bandgap energies from visible to infrared, 1-3) unique phenomena related to spin-valley physics, 4,5) and single-photon emission. [6][7][8][9] In particular, defect-derived excitonic states have recently received much attention for their applications in single-photon emitters. To date, several groups have reported that atomic-layer TMDCs show photoluminescence (PL) from optically active defects at low temperature (4 ∼ 90 K). 6-11) Such a two-dimensional (2D) single-quantum emission has practical advantages in efficient photon extraction and high integration capability. However, the details of such defect sites are still unclear, and PL can generally be observed only at low temperature. These issues may be resolved by the controlled fabrication of defect states, which is an important challenge in understanding and using TMDC atomic layers as quantum light sources.In general, defect states in low-dimensional materials are created through several mechanisms, including atomic vacancy formation, 12) impurity doping, [13][14][15][16] and chemical functionalization. 17) In this study, we have investigated impuritydoped WS 2 monolayers as a model system. Monolayer WS 2 is a semiconductor with a relatively wide direct bandgap and high air stability, and there have been many reports on its growth process and characterization. 10,[18][19][20][21][22] To implant impurities in WS 2 , we employed halide-assisted chemical vapor deposition (CVD), which was recently developed by Li et al. 21) This method can produce large-area monolayer WS 2 at relatively low temperatures (700°C) and under atmospheric pressure. Importantly, the use of halides can effectively transport precursors of transition metals, which usually have very low vapor pressure. As an impurity, Mo atoms are well studied and cause bandgap narrowing through the substitution of W sites in monolayer WS 2 . 14,15,23,24) However, there are very few studies on the doping of other transition metals for monolayer TMDCs. In the present study, Nb is selected because its atomic size is comparable to that of Mo and it is reported to generate acceptor states for some TMDCs. 16,25) Here, we report the synthesis and characterization of monolayer impurity-doped WS 2 using halide-ass...

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Growth and optical properties of Nb-doped WS₂ monolayers

Sasaki

Kobayashi

Liu³

et al. 2016

Appl. Phys. Express

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“…[1][2][3][4][5][6][7][8] Depending on the arrangement of its S atoms, monolayer MoS 2 appears in many distinct phases, two of them are more popular and exhibits substantially different electronic structures: 2H (trigonal prismatic, D 3h ) MoS 2 is a semiconductor with a finite band gap between the filled d z 2 and empty d x 2 − d y 2 ,xy bands, and 1T (octahedral geometry, O h ) phase is metallic with Fermi level lying in the middle of degenerate d xy,yz,xz single band. 9 It has been recently demonstrated that the reversible transition from 2H to 1 T phase can be achieved in monolayer MoS 2 by annealing, 10 electric doping, 11,12 applying strain 13 or electron-beam irradiating.…”

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Structural, mechanical and electronic properties of in-plane 1T/2H phase interface of MoS2 heterostructures

et al. 2015

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Two-dimensional (2D) molybdenum disulfide (MoS2) phase hybrid system composed by 2H and 1T phase is a natural metal/semiconductor heterostructures and promised a wide range of potential applications. Here, we report the first principle investigations on the structural, mechanical and electronic properties of hybrid system with armchair (AC) and zigzag (ZZ) interfaces. The ZZ type 1T/2H interface are more energy favorable than AC type interface with 3.39 eV/nm. Similar with that of bulked 1T MoS2, the intrinsic strengths of the heterostructures are lower than that of the bulk 2H, especially for that with ZZ interface. Analysis of density of states shows that the electronic properties gradually transmitted from the metallic 1T phase to the semiconducting 2H phase for the structural abrupt interface. The present theoretical results constitute a useful picture for the 2D electronic devices using current MoS2 1T/2H heterostructures and provide vital insights into the other 2D hybrid materials.

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“…Photoluminescence (PL) characterization of the Mo (1-x) W x S 2 monolayer alloys has shown the continuously tuned emission from 1.82 eV (reached at x ¼ 0.20) to 1.99 eV (reached at x ¼ 1). 8,9 Moreover, centimeter-scale and highquality Mo 0.5 W 0.5 Se 2 alloy films were obtained on both a rigid SiO 2 /Si substrate and a flexible polyimide (PI) substrate. 10 For the second type of alloy, two different chalcogen atoms present in the alloy [MoS 2(1-x) Se 2x (Refs.…”

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DFT study of structural and electronic properties of MoS2(1−x)Se2x alloy (x = 0.25)

Gusakova

Gusakov²,

Tay

2018

Journal of Applied Physics

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First-principles calculations have been performed to study the structural features of the monolayer MoS2(1-x)Se2x (x = 0.25) alloy and its electronic properties. We studied the effects of the relative positions of Se atoms in a real monolayer alloy. It was demonstrated that the distribution of the Se atoms between the top and bottom chalcogen planes was most energetically favorable. For a more probable distribution of Se atoms, a MoS2(1-x)Se2x (x = 0.25) monolayer alloy is a direct semiconductor with a fundamental band gap equal to 2.35 eV (calculated with the GVJ-2e method). We also evaluated the optical band gap of the alloy at 77 K (1.86 eV) and at room temperature (1.80 eV), which was in good agreement with the experimentally measured band gap of 1.79 eV.

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Tunable Band Gap Photoluminescence from Atomically Thin Transition-Metal Dichalcogenide Alloys

Cited by 565 publications

References 51 publications

Growth and optical properties of Nb-doped WS₂ monolayers

Growth and optical properties of Nb-doped WS₂ monolayers

Structural, mechanical and electronic properties of in-plane 1T/2H phase interface of MoS2 heterostructures

DFT study of structural and electronic properties of MoS2(1−x)Se2x alloy (x = 0.25)

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Tunable Band Gap Photoluminescence from Atomically Thin Transition-Metal Dichalcogenide Alloys

Cited by 565 publications

References 51 publications

Growth and optical properties of Nb-doped WS2 monolayers

Growth and optical properties of Nb-doped WS2 monolayers

Structural, mechanical and electronic properties of in-plane 1T/2H phase interface of MoS2 heterostructures

DFT study of structural and electronic properties of MoS2(1−x)Se2x alloy (x = 0.25)

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Growth and optical properties of Nb-doped WS₂ monolayers

Growth and optical properties of Nb-doped WS₂ monolayers