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Controllable synthesis of molybdenum tungsten disulfide alloy for vertically composition-controlled multilayer.

Song JG, Ryu GH, Lee SJ, Sim S, Lee CW, Choi T, Jung H, Kim Y, Lee Z, Myoung JM, Dussarrat C, Lansalot-Matras C, Park J, Choi H, Kim H - Nat Commun (2015)

Bottom Line: The effective synthesis of two-dimensional transition metal dichalcogenides alloy is essential for successful application in electronic and optical devices based on a tunable band gap.Various spectroscopic and microscopic results indicate that the synthesized Mo1-xWxS2 alloys have complete mixing of Mo and W atoms and tunable band gap by systematically controlled composition and layer number.Further, we demonstrate that a VCC Mo1-xWxS2 multilayer photodetector generates three to four times greater photocurrent than MoS2- and WS2-based devices, owing to the broadband light absorption.

View Article: PubMed Central - PubMed

Affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.

ABSTRACT
The effective synthesis of two-dimensional transition metal dichalcogenides alloy is essential for successful application in electronic and optical devices based on a tunable band gap. Here we show a synthesis process for Mo1-xWxS2 alloy using sulfurization of super-cycle atomic layer deposition Mo1-xWxOy. Various spectroscopic and microscopic results indicate that the synthesized Mo1-xWxS2 alloys have complete mixing of Mo and W atoms and tunable band gap by systematically controlled composition and layer number. Based on this, we synthesize a vertically composition-controlled (VCC) Mo1-xWxS2 multilayer using five continuous super-cycles with different cycle ratios for each super-cycle. Angle-resolved X-ray photoemission spectroscopy, Raman and ultraviolet-visible spectrophotometer results reveal that a VCC Mo1-xWxS2 multilayer has different vertical composition and broadband light absorption with strong interlayer coupling within a VCC Mo1-xWxS2 multilayer. Further, we demonstrate that a VCC Mo1-xWxS2 multilayer photodetector generates three to four times greater photocurrent than MoS2- and WS2-based devices, owing to the broadband light absorption.

No MeSH data available.


Synthesis and XPS of Mo1−xWxS2 alloy.(a) Synthesis procedure of super-cycle ALD for Mo1−xWxS2 alloy. XPS measurements for (b) Mo3d, (c) W4f and (d) S2p core levels in the 1l Mo1−xWxS2 alloy with different n and m numbers in one super-cycle. All measured XPS results are normalized by S2p3/2 peak intensity.
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f3: Synthesis and XPS of Mo1−xWxS2 alloy.(a) Synthesis procedure of super-cycle ALD for Mo1−xWxS2 alloy. XPS measurements for (b) Mo3d, (c) W4f and (d) S2p core levels in the 1l Mo1−xWxS2 alloy with different n and m numbers in one super-cycle. All measured XPS results are normalized by S2p3/2 peak intensity.

Mentions: A super-cycle ALD-based Mo1−xWxS2 alloy synthesis process was developed based on the synthesis processes for 2D MoS2 (this study) and WS2 (previous study)30. The overall synthesis scheme for the Mo1−xWxS2 alloy is illustrated in Fig. 3a. First, we conducted 10 cycles of WO3 ALD to address the nucleation delay of the ALD WO3 (ref. 30) (not shown in Fig. 3a). Subsequently, one super-cycle ALD process consisting of n cycles of ALD MoOx and m cycles of ALD WO3 was conducted and the deposited Mo1−xWxOy alloy thin films were sulfurized. We used varying cycles for MoOx (n) and WO3 (m) in one super-cycle to deposit 0.8−0.9-nm-thick composition-controlled Mo1−xWxOy alloy thin films to create a 1l Mo1−xWxS2 alloy. This was based on the growth rate of ALD MoOx (2.7 Å per cycle) and WO3 (0.9 Å per cycle), as shown in Supplementary Table 1. Figure 3b–d shows the XPS spectra of the 1l MoS2, 1l WS2 and sulfurized Mo1−xWxOy alloy thin films with different n and m numbers in one super-cycle. All measured XPS results were normalized by S2p3/2 peak intensity and calibrated to the C1s peak at 285 eV. With increasing n/m ratio, the intensity of the Mo3d peaks increased, while the W5p3/2 and W4f peaks decreased. Furthermore, the peak positions for Mo3d and W4f gradually shifted to higher binding energies, from 232.2 eV and 229.1 eV to 232.5 eV and 229.4 eV for Mo3d3/2 and Mo3d5/2, respectively, and from 34.8 eV and 32.6 eV to 35.0 eV and 32.8 eV for W4f5/2 and W4f7/2, respectively. In addition, the S2p peaks shifted to lower binding energies, from 163.5 eV and 162.4 eV to 163.3 eV and 162.2 eV for S2p1/2 and S2p3/2, respectively. This small shift in peak position is attributed to the enhanced electron attraction strength of S and the reduced electron attraction strength of W, following increased Mo content due to smaller electronegativity of Mo (2.16) than that of W (2.36) as previously reported7. It is noteworthy that the Mo6+ 3d3/2 peak, which is attributed to the Mo–O bonding, is not observed in the Mo3d spectra; this indicates the absence of O species.


Controllable synthesis of molybdenum tungsten disulfide alloy for vertically composition-controlled multilayer.

Song JG, Ryu GH, Lee SJ, Sim S, Lee CW, Choi T, Jung H, Kim Y, Lee Z, Myoung JM, Dussarrat C, Lansalot-Matras C, Park J, Choi H, Kim H - Nat Commun (2015)

Synthesis and XPS of Mo1−xWxS2 alloy.(a) Synthesis procedure of super-cycle ALD for Mo1−xWxS2 alloy. XPS measurements for (b) Mo3d, (c) W4f and (d) S2p core levels in the 1l Mo1−xWxS2 alloy with different n and m numbers in one super-cycle. All measured XPS results are normalized by S2p3/2 peak intensity.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f3: Synthesis and XPS of Mo1−xWxS2 alloy.(a) Synthesis procedure of super-cycle ALD for Mo1−xWxS2 alloy. XPS measurements for (b) Mo3d, (c) W4f and (d) S2p core levels in the 1l Mo1−xWxS2 alloy with different n and m numbers in one super-cycle. All measured XPS results are normalized by S2p3/2 peak intensity.
Mentions: A super-cycle ALD-based Mo1−xWxS2 alloy synthesis process was developed based on the synthesis processes for 2D MoS2 (this study) and WS2 (previous study)30. The overall synthesis scheme for the Mo1−xWxS2 alloy is illustrated in Fig. 3a. First, we conducted 10 cycles of WO3 ALD to address the nucleation delay of the ALD WO3 (ref. 30) (not shown in Fig. 3a). Subsequently, one super-cycle ALD process consisting of n cycles of ALD MoOx and m cycles of ALD WO3 was conducted and the deposited Mo1−xWxOy alloy thin films were sulfurized. We used varying cycles for MoOx (n) and WO3 (m) in one super-cycle to deposit 0.8−0.9-nm-thick composition-controlled Mo1−xWxOy alloy thin films to create a 1l Mo1−xWxS2 alloy. This was based on the growth rate of ALD MoOx (2.7 Å per cycle) and WO3 (0.9 Å per cycle), as shown in Supplementary Table 1. Figure 3b–d shows the XPS spectra of the 1l MoS2, 1l WS2 and sulfurized Mo1−xWxOy alloy thin films with different n and m numbers in one super-cycle. All measured XPS results were normalized by S2p3/2 peak intensity and calibrated to the C1s peak at 285 eV. With increasing n/m ratio, the intensity of the Mo3d peaks increased, while the W5p3/2 and W4f peaks decreased. Furthermore, the peak positions for Mo3d and W4f gradually shifted to higher binding energies, from 232.2 eV and 229.1 eV to 232.5 eV and 229.4 eV for Mo3d3/2 and Mo3d5/2, respectively, and from 34.8 eV and 32.6 eV to 35.0 eV and 32.8 eV for W4f5/2 and W4f7/2, respectively. In addition, the S2p peaks shifted to lower binding energies, from 163.5 eV and 162.4 eV to 163.3 eV and 162.2 eV for S2p1/2 and S2p3/2, respectively. This small shift in peak position is attributed to the enhanced electron attraction strength of S and the reduced electron attraction strength of W, following increased Mo content due to smaller electronegativity of Mo (2.16) than that of W (2.36) as previously reported7. It is noteworthy that the Mo6+ 3d3/2 peak, which is attributed to the Mo–O bonding, is not observed in the Mo3d spectra; this indicates the absence of O species.

Bottom Line: The effective synthesis of two-dimensional transition metal dichalcogenides alloy is essential for successful application in electronic and optical devices based on a tunable band gap.Various spectroscopic and microscopic results indicate that the synthesized Mo1-xWxS2 alloys have complete mixing of Mo and W atoms and tunable band gap by systematically controlled composition and layer number.Further, we demonstrate that a VCC Mo1-xWxS2 multilayer photodetector generates three to four times greater photocurrent than MoS2- and WS2-based devices, owing to the broadband light absorption.

View Article: PubMed Central - PubMed

Affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.

ABSTRACT
The effective synthesis of two-dimensional transition metal dichalcogenides alloy is essential for successful application in electronic and optical devices based on a tunable band gap. Here we show a synthesis process for Mo1-xWxS2 alloy using sulfurization of super-cycle atomic layer deposition Mo1-xWxOy. Various spectroscopic and microscopic results indicate that the synthesized Mo1-xWxS2 alloys have complete mixing of Mo and W atoms and tunable band gap by systematically controlled composition and layer number. Based on this, we synthesize a vertically composition-controlled (VCC) Mo1-xWxS2 multilayer using five continuous super-cycles with different cycle ratios for each super-cycle. Angle-resolved X-ray photoemission spectroscopy, Raman and ultraviolet-visible spectrophotometer results reveal that a VCC Mo1-xWxS2 multilayer has different vertical composition and broadband light absorption with strong interlayer coupling within a VCC Mo1-xWxS2 multilayer. Further, we demonstrate that a VCC Mo1-xWxS2 multilayer photodetector generates three to four times greater photocurrent than MoS2- and WS2-based devices, owing to the broadband light absorption.

No MeSH data available.