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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.


Atomic arrangement and mixture of Mo0.4W0.6S2 alloy.(a) HRTEM image of 1l Mo0.4W0.6S2 alloy at a selected region, and (inset) FFT pattern. Scale bars, 2 nm. (b) STEM-ADF image of 1l Mo0.4W0.6S2 alloy at a selected region and (c) corresponding EDX spectrum. Scale bars, 1 nm. (d) Inverse FFT image with masking applied to yellow dashed square region in b. Scale bars, 1 nm. (e) Intensity profile of yellow solid line in d. (f) Coloured W atoms with light brown, blue, red, dark red, yellow, green and violet for six, five, four, three, two, one and zero number of neighbouring Mo atoms.
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f5: Atomic arrangement and mixture of Mo0.4W0.6S2 alloy.(a) HRTEM image of 1l Mo0.4W0.6S2 alloy at a selected region, and (inset) FFT pattern. Scale bars, 2 nm. (b) STEM-ADF image of 1l Mo0.4W0.6S2 alloy at a selected region and (c) corresponding EDX spectrum. Scale bars, 1 nm. (d) Inverse FFT image with masking applied to yellow dashed square region in b. Scale bars, 1 nm. (e) Intensity profile of yellow solid line in d. (f) Coloured W atoms with light brown, blue, red, dark red, yellow, green and violet for six, five, four, three, two, one and zero number of neighbouring Mo atoms.

Mentions: Figure 5a is the HRTEM image of the 1l Mo0.4W0.6S2 alloy (x=0.6). The Mo0.4W0.6S2 alloy shows a periodic atomic arrangement with a honeycomb-like structure and sixfold coordination symmetry, similar to the 1l MoS2 shown in Fig. 2f. To distinguish between the W and Mo atoms in the 1l Mo0.4W0.6S2 alloy, we analysed the Mo0.4W0.6S2 alloy using STEM annular dark-field and energy dispersive X-ray spectrometry (EDX). Figure 5b is the STEM-ADF image of the 1l Mo0.4W0.6S2 alloy. Brighter and less bright spots, which correspond to W and Mo atoms, respectively, are clearly resolved in the ADF image, as previously reported44. The calculated Mo/W ratio from the atom count in Fig. 5b is 0.42:0.58, which differs by <5% from the XPS-measured stoichiometry. In addition, the EDX result in Fig. 5c supports the presence of W, Mo and S species in the 1l Mo0.4W0.6S2 alloy. To extract a clear intensity difference between the W and Mo atoms, we performed an inverse FFT by applying a mask to the yellow dashed square region in Fig. 5b. Figure 5d–e shows the inversed FFT image (Fig. 5d) and intensity profile (Fig. 5e) along with the yellow solid line in Fig. 5d. Although S atoms are not distinguishable in our result as a result of the displacement of S atoms at 200 kV operation voltage by the knock-on mechanism45, the W and Mo atoms are clearly observable, confirming that these elements share the metal atom sites44. The preference for Mo or W atoms at the neighbouring sites of W atoms is evaluated by degree of alloying that can be calculated by Equation (2)2344,


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)

Atomic arrangement and mixture of Mo0.4W0.6S2 alloy.(a) HRTEM image of 1l Mo0.4W0.6S2 alloy at a selected region, and (inset) FFT pattern. Scale bars, 2 nm. (b) STEM-ADF image of 1l Mo0.4W0.6S2 alloy at a selected region and (c) corresponding EDX spectrum. Scale bars, 1 nm. (d) Inverse FFT image with masking applied to yellow dashed square region in b. Scale bars, 1 nm. (e) Intensity profile of yellow solid line in d. (f) Coloured W atoms with light brown, blue, red, dark red, yellow, green and violet for six, five, four, three, two, one and zero number of neighbouring Mo atoms.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4525162&req=5

f5: Atomic arrangement and mixture of Mo0.4W0.6S2 alloy.(a) HRTEM image of 1l Mo0.4W0.6S2 alloy at a selected region, and (inset) FFT pattern. Scale bars, 2 nm. (b) STEM-ADF image of 1l Mo0.4W0.6S2 alloy at a selected region and (c) corresponding EDX spectrum. Scale bars, 1 nm. (d) Inverse FFT image with masking applied to yellow dashed square region in b. Scale bars, 1 nm. (e) Intensity profile of yellow solid line in d. (f) Coloured W atoms with light brown, blue, red, dark red, yellow, green and violet for six, five, four, three, two, one and zero number of neighbouring Mo atoms.
Mentions: Figure 5a is the HRTEM image of the 1l Mo0.4W0.6S2 alloy (x=0.6). The Mo0.4W0.6S2 alloy shows a periodic atomic arrangement with a honeycomb-like structure and sixfold coordination symmetry, similar to the 1l MoS2 shown in Fig. 2f. To distinguish between the W and Mo atoms in the 1l Mo0.4W0.6S2 alloy, we analysed the Mo0.4W0.6S2 alloy using STEM annular dark-field and energy dispersive X-ray spectrometry (EDX). Figure 5b is the STEM-ADF image of the 1l Mo0.4W0.6S2 alloy. Brighter and less bright spots, which correspond to W and Mo atoms, respectively, are clearly resolved in the ADF image, as previously reported44. The calculated Mo/W ratio from the atom count in Fig. 5b is 0.42:0.58, which differs by <5% from the XPS-measured stoichiometry. In addition, the EDX result in Fig. 5c supports the presence of W, Mo and S species in the 1l Mo0.4W0.6S2 alloy. To extract a clear intensity difference between the W and Mo atoms, we performed an inverse FFT by applying a mask to the yellow dashed square region in Fig. 5b. Figure 5d–e shows the inversed FFT image (Fig. 5d) and intensity profile (Fig. 5e) along with the yellow solid line in Fig. 5d. Although S atoms are not distinguishable in our result as a result of the displacement of S atoms at 200 kV operation voltage by the knock-on mechanism45, the W and Mo atoms are clearly observable, confirming that these elements share the metal atom sites44. The preference for Mo or W atoms at the neighbouring sites of W atoms is evaluated by degree of alloying that can be calculated by Equation (2)2344,

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.