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Charge-transfer-based gas sensing using atomic-layer MoS2.

Cho B, Hahm MG, Choi M, Yoon J, Kim AR, Lee YJ, Park SG, Kwon JD, Kim CS, Song M, Jeong Y, Nam KS, Lee S, Yoo TJ, Kang CG, Lee BH, Ko HC, Ajayan PM, Kim DH - Sci Rep (2015)

Bottom Line: First-principles density functional theory calculations indicated that NO2 and NH3 molecules have negative adsorption energies (i.e., the adsorption processes are exothermic).Thus, NO2 and NH3 molecules are likely to adsorb onto the surface of the MoS2.The in situ PL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2 and the gas molecules.

View Article: PubMed Central - PubMed

Affiliation: Advanced Functional Thin Films Department, Surface Technology Division, Korea Institute of Materials Science (KIMS), 797 Changwondaero, Sungsan-Gu, Changwon, Gyeongnam 642-831, Republic of Korea.

ABSTRACT
Two-dimensional (2D) molybdenum disulphide (MoS2) atomic layers have a strong potential to be used as 2D electronic sensor components. However, intrinsic synthesis challenges have made this task difficult. In addition, the detection mechanisms for gas molecules are not fully understood. Here, we report a high-performance gas sensor constructed using atomic-layered MoS2 synthesised by chemical vapour deposition (CVD). A highly sensitive and selective gas sensor based on the CVD-synthesised MoS2 was developed. In situ photoluminescence characterisation revealed the charge transfer mechanism between the gas molecules and MoS2, which was validated by theoretical calculations. First-principles density functional theory calculations indicated that NO2 and NH3 molecules have negative adsorption energies (i.e., the adsorption processes are exothermic). Thus, NO2 and NH3 molecules are likely to adsorb onto the surface of the MoS2. The in situ PL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2 and the gas molecules.

No MeSH data available.


Related in: MedlinePlus

Large-scale synthesis of MoS2.(a) Schematic of the atomic-layered MoS2. The quasi-2D MoS2 was occupied by one Mo (a trigonal prismatic structure) and two S atoms (hexagonal planes). (b) Image of the as-synthesised MoS2 film on the 2-inch sapphire substrate. The as-synthesised MoS2 film was semi-transparent. (c) Cross-sectional TEM images of the as-grown MoS2 films. The image clearly demonstrates that the synthesised MoS2 films consisted of three layers of MoS2. (d) Raman spectrum of the triple-layered MoS2. The spectrum reveals a strong in-plane vibrational mode for the Mo and S atoms (E2g) and an out-of-plane vibrational mode for the S atoms (A1g). The peak position difference (Δ) between the E2g and A1g bands is approximately 22.9, indicating triple-layered MoS2. (e, f) Raman maps of E2g (blue) and A1g (red), respectively. The Raman mapping area was 50 × 50 μm2 with 0.3 μm steps. The Raman images show the spatial distribution on the surface of the substrates.
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f1: Large-scale synthesis of MoS2.(a) Schematic of the atomic-layered MoS2. The quasi-2D MoS2 was occupied by one Mo (a trigonal prismatic structure) and two S atoms (hexagonal planes). (b) Image of the as-synthesised MoS2 film on the 2-inch sapphire substrate. The as-synthesised MoS2 film was semi-transparent. (c) Cross-sectional TEM images of the as-grown MoS2 films. The image clearly demonstrates that the synthesised MoS2 films consisted of three layers of MoS2. (d) Raman spectrum of the triple-layered MoS2. The spectrum reveals a strong in-plane vibrational mode for the Mo and S atoms (E2g) and an out-of-plane vibrational mode for the S atoms (A1g). The peak position difference (Δ) between the E2g and A1g bands is approximately 22.9, indicating triple-layered MoS2. (e, f) Raman maps of E2g (blue) and A1g (red), respectively. The Raman mapping area was 50 × 50 μm2 with 0.3 μm steps. The Raman images show the spatial distribution on the surface of the substrates.

Mentions: Most approaches use direct/indirect sulphurisation of Mo-containing thin films to synthesise atomic-layered MoS2 thin films. The precursor is a key factor in the synthesis of MoS2. In previous studies, most authors adopted one of three precursors: molybdenum thin films16; molybdenum trioxide17; or ammonium thiomolybdate18. However, previous methods have involved complex precursor preparations, yielding films with inconsistent quality. In our search for strategies for synthesising uniform wafer-scale MoS2 (see schematic in Fig. 1a), we have focused on the development of a thermal CVD system and process. Atomic-layered MoS2 was grown using molybdenum trioxide (MoO3) deposited onto a sapphire substrate and a sulphur powder source. The sublimated sulphur served as a precursor to sulphurise the MoO3 film. To achieve our overall goal of preparing MoS2 films of consistent quality on the desired substrates, we turned our attention to pressure control during the CVD reaction. A recent report indicated that an increase in the amount of either Mo or S atoms results in increased formation of energetically favourable defects on the MoS2 surface during film growth19. Thus, we systematically controlled the reaction pressure to provide sufficient sublimated sulphur using a custom-made automatic pressure control system (Supplementary Fig. S1).


Charge-transfer-based gas sensing using atomic-layer MoS2.

Cho B, Hahm MG, Choi M, Yoon J, Kim AR, Lee YJ, Park SG, Kwon JD, Kim CS, Song M, Jeong Y, Nam KS, Lee S, Yoo TJ, Kang CG, Lee BH, Ko HC, Ajayan PM, Kim DH - Sci Rep (2015)

Large-scale synthesis of MoS2.(a) Schematic of the atomic-layered MoS2. The quasi-2D MoS2 was occupied by one Mo (a trigonal prismatic structure) and two S atoms (hexagonal planes). (b) Image of the as-synthesised MoS2 film on the 2-inch sapphire substrate. The as-synthesised MoS2 film was semi-transparent. (c) Cross-sectional TEM images of the as-grown MoS2 films. The image clearly demonstrates that the synthesised MoS2 films consisted of three layers of MoS2. (d) Raman spectrum of the triple-layered MoS2. The spectrum reveals a strong in-plane vibrational mode for the Mo and S atoms (E2g) and an out-of-plane vibrational mode for the S atoms (A1g). The peak position difference (Δ) between the E2g and A1g bands is approximately 22.9, indicating triple-layered MoS2. (e, f) Raman maps of E2g (blue) and A1g (red), respectively. The Raman mapping area was 50 × 50 μm2 with 0.3 μm steps. The Raman images show the spatial distribution on the surface of the substrates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4307013&req=5

f1: Large-scale synthesis of MoS2.(a) Schematic of the atomic-layered MoS2. The quasi-2D MoS2 was occupied by one Mo (a trigonal prismatic structure) and two S atoms (hexagonal planes). (b) Image of the as-synthesised MoS2 film on the 2-inch sapphire substrate. The as-synthesised MoS2 film was semi-transparent. (c) Cross-sectional TEM images of the as-grown MoS2 films. The image clearly demonstrates that the synthesised MoS2 films consisted of three layers of MoS2. (d) Raman spectrum of the triple-layered MoS2. The spectrum reveals a strong in-plane vibrational mode for the Mo and S atoms (E2g) and an out-of-plane vibrational mode for the S atoms (A1g). The peak position difference (Δ) between the E2g and A1g bands is approximately 22.9, indicating triple-layered MoS2. (e, f) Raman maps of E2g (blue) and A1g (red), respectively. The Raman mapping area was 50 × 50 μm2 with 0.3 μm steps. The Raman images show the spatial distribution on the surface of the substrates.
Mentions: Most approaches use direct/indirect sulphurisation of Mo-containing thin films to synthesise atomic-layered MoS2 thin films. The precursor is a key factor in the synthesis of MoS2. In previous studies, most authors adopted one of three precursors: molybdenum thin films16; molybdenum trioxide17; or ammonium thiomolybdate18. However, previous methods have involved complex precursor preparations, yielding films with inconsistent quality. In our search for strategies for synthesising uniform wafer-scale MoS2 (see schematic in Fig. 1a), we have focused on the development of a thermal CVD system and process. Atomic-layered MoS2 was grown using molybdenum trioxide (MoO3) deposited onto a sapphire substrate and a sulphur powder source. The sublimated sulphur served as a precursor to sulphurise the MoO3 film. To achieve our overall goal of preparing MoS2 films of consistent quality on the desired substrates, we turned our attention to pressure control during the CVD reaction. A recent report indicated that an increase in the amount of either Mo or S atoms results in increased formation of energetically favourable defects on the MoS2 surface during film growth19. Thus, we systematically controlled the reaction pressure to provide sufficient sublimated sulphur using a custom-made automatic pressure control system (Supplementary Fig. S1).

Bottom Line: First-principles density functional theory calculations indicated that NO2 and NH3 molecules have negative adsorption energies (i.e., the adsorption processes are exothermic).Thus, NO2 and NH3 molecules are likely to adsorb onto the surface of the MoS2.The in situ PL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2 and the gas molecules.

View Article: PubMed Central - PubMed

Affiliation: Advanced Functional Thin Films Department, Surface Technology Division, Korea Institute of Materials Science (KIMS), 797 Changwondaero, Sungsan-Gu, Changwon, Gyeongnam 642-831, Republic of Korea.

ABSTRACT
Two-dimensional (2D) molybdenum disulphide (MoS2) atomic layers have a strong potential to be used as 2D electronic sensor components. However, intrinsic synthesis challenges have made this task difficult. In addition, the detection mechanisms for gas molecules are not fully understood. Here, we report a high-performance gas sensor constructed using atomic-layered MoS2 synthesised by chemical vapour deposition (CVD). A highly sensitive and selective gas sensor based on the CVD-synthesised MoS2 was developed. In situ photoluminescence characterisation revealed the charge transfer mechanism between the gas molecules and MoS2, which was validated by theoretical calculations. First-principles density functional theory calculations indicated that NO2 and NH3 molecules have negative adsorption energies (i.e., the adsorption processes are exothermic). Thus, NO2 and NH3 molecules are likely to adsorb onto the surface of the MoS2. The in situ PL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2 and the gas molecules.

No MeSH data available.


Related in: MedlinePlus