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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.


Adsorption configurations and in situ PL.(a, b) Top views of the most favourable configurations for NO2 (a) and NH3 (b) on the MoS2. The calculated adsorption energies were −0.14 eV for NO2 and −0.16 eV for NH3. The negative adsorption energies indicate that the adsorption process is exothermic, indicating that NO2 and NH3 molecules are likely to be adsorbed onto the surface of the MoS2. (c, d) In situ PL spectra recorded from the MoS2 with NO2 (c) and NH3 (d) molecules. The overall intensity of the PL spectra changes in the presence of NO2 and NH3 molecules. The PL intensities of the A+ trions and A0 excitons are either suppressed or increased by changes in the concentrations of the charge carriers. (e, f) Schematics of the charge density differences for MoS2 in the presence of NO2 (e) and NH3 (f) gas molecules. NO2 molecules on the surface of MoS2 act as electron acceptors, whereas NH3 molecules act as electron donors.
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f3: Adsorption configurations and in situ PL.(a, b) Top views of the most favourable configurations for NO2 (a) and NH3 (b) on the MoS2. The calculated adsorption energies were −0.14 eV for NO2 and −0.16 eV for NH3. The negative adsorption energies indicate that the adsorption process is exothermic, indicating that NO2 and NH3 molecules are likely to be adsorbed onto the surface of the MoS2. (c, d) In situ PL spectra recorded from the MoS2 with NO2 (c) and NH3 (d) molecules. The overall intensity of the PL spectra changes in the presence of NO2 and NH3 molecules. The PL intensities of the A+ trions and A0 excitons are either suppressed or increased by changes in the concentrations of the charge carriers. (e, f) Schematics of the charge density differences for MoS2 in the presence of NO2 (e) and NH3 (f) gas molecules. NO2 molecules on the surface of MoS2 act as electron acceptors, whereas NH3 molecules act as electron donors.

Mentions: To explore the gas adsorption characteristics of the MoS2, we adopted theoretical and experimental approaches. First-principles density functional theory (DFT) calculations were conducted using the screened hybrid functional of Heyd-Scuseria-Ernzerhof with the D2 correction for van der Waals interactions2627 (see the detailed methods in the Supplementary Information). To simulate NO2 and NH3 adsorption onto the MoS2 monolayer, supercells containing 16 Mo and 32 S atoms with NO2 and NH3 were employed using a 2 × 2 × 1 k-point grid. The most stable configurations of NO2 and NH3 reported in a recent study that compared the total energy between different adsorption configurations28 were considered. The NO2 and NH3 molecules were preferentially adsorbed onto the top of the hexagon of the MoS228 (Figs. 3a and b). The adsorption energies of the NO2 and NH3 gas molecules were evaluated using , where is the total energy of a supercell containing both an MoS2 monolayer and a gas molecule (NO2 or NH3), is the total energy of the host MoS2 supercell, and E(molecule) is the total energy of a supercell containing a gas molecule. The calculated adsorption energies of NO2 and NH3 were −0.14 eV and −0.16 eV, respectively. These values were ~0.1 eV smaller than the values obtained using the local density approximation (LDA) because the LDA functional overestimates the adsorption energy28. The negative adsorption energies indicate that the adsorption process is exothermic. Thus, NO2 and NH3 molecules are likely to be adsorbed onto the surface of MoS2.


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)

Adsorption configurations and in situ PL.(a, b) Top views of the most favourable configurations for NO2 (a) and NH3 (b) on the MoS2. The calculated adsorption energies were −0.14 eV for NO2 and −0.16 eV for NH3. The negative adsorption energies indicate that the adsorption process is exothermic, indicating that NO2 and NH3 molecules are likely to be adsorbed onto the surface of the MoS2. (c, d) In situ PL spectra recorded from the MoS2 with NO2 (c) and NH3 (d) molecules. The overall intensity of the PL spectra changes in the presence of NO2 and NH3 molecules. The PL intensities of the A+ trions and A0 excitons are either suppressed or increased by changes in the concentrations of the charge carriers. (e, f) Schematics of the charge density differences for MoS2 in the presence of NO2 (e) and NH3 (f) gas molecules. NO2 molecules on the surface of MoS2 act as electron acceptors, whereas NH3 molecules act as electron donors.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Adsorption configurations and in situ PL.(a, b) Top views of the most favourable configurations for NO2 (a) and NH3 (b) on the MoS2. The calculated adsorption energies were −0.14 eV for NO2 and −0.16 eV for NH3. The negative adsorption energies indicate that the adsorption process is exothermic, indicating that NO2 and NH3 molecules are likely to be adsorbed onto the surface of the MoS2. (c, d) In situ PL spectra recorded from the MoS2 with NO2 (c) and NH3 (d) molecules. The overall intensity of the PL spectra changes in the presence of NO2 and NH3 molecules. The PL intensities of the A+ trions and A0 excitons are either suppressed or increased by changes in the concentrations of the charge carriers. (e, f) Schematics of the charge density differences for MoS2 in the presence of NO2 (e) and NH3 (f) gas molecules. NO2 molecules on the surface of MoS2 act as electron acceptors, whereas NH3 molecules act as electron donors.
Mentions: To explore the gas adsorption characteristics of the MoS2, we adopted theoretical and experimental approaches. First-principles density functional theory (DFT) calculations were conducted using the screened hybrid functional of Heyd-Scuseria-Ernzerhof with the D2 correction for van der Waals interactions2627 (see the detailed methods in the Supplementary Information). To simulate NO2 and NH3 adsorption onto the MoS2 monolayer, supercells containing 16 Mo and 32 S atoms with NO2 and NH3 were employed using a 2 × 2 × 1 k-point grid. The most stable configurations of NO2 and NH3 reported in a recent study that compared the total energy between different adsorption configurations28 were considered. The NO2 and NH3 molecules were preferentially adsorbed onto the top of the hexagon of the MoS228 (Figs. 3a and b). The adsorption energies of the NO2 and NH3 gas molecules were evaluated using , where is the total energy of a supercell containing both an MoS2 monolayer and a gas molecule (NO2 or NH3), is the total energy of the host MoS2 supercell, and E(molecule) is the total energy of a supercell containing a gas molecule. The calculated adsorption energies of NO2 and NH3 were −0.14 eV and −0.16 eV, respectively. These values were ~0.1 eV smaller than the values obtained using the local density approximation (LDA) because the LDA functional overestimates the adsorption energy28. The negative adsorption energies indicate that the adsorption process is exothermic. Thus, NO2 and NH3 molecules are likely to be adsorbed onto the surface of MoS2.

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.