Journal
ACS NANO
Volume 9, Issue 9, Pages 9314-9321Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.5b04504
Keywords
MoS2; 2D material; chemical vapor deposition; gas adsorption; density functional theory
Categories
Funding
- National Research Foundation of Korea (NRF) - Ministry of Science, ICT, and Future Planning, Korea (MISP) [2015R1A2A1A05001844]
- Global Frontier Research Center for Advanced Soft Electronics (MISP) [2014M3A6A5060937]
- Climate Change Research Hub of KAIST [N01150139]
- Basic Science Research Program through the National Research Foundation of Korea (NRF) - Ministry of Education [2014R1A1A2055853]
- National Research Foundation of Korea [2014R1A1A2055853] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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In this work, we demonstrate that gas adsorption is significantly higher in edge sites of vertically aligned MoS2 compared to that of the conventional basal plane exposed MoS2 films. To compare the effect of the alignment of MoS2 on the gas adsorption properties, we synthesized three distinct MoS2 films with different alignment directions ((1) horizontally aligned MoS2 (basal plane exposed), (2) mixture of horizontally aligned MoS2 and vertically aligned layers (basal and edge exposed), and (3) vertically aligned MoS2 (edge exposed)) by using rapid sulfurization method of CVD process. Vertically aligned MoS2 film shows about 5-fold enhanced sensitivity to NO2 gas molecules compared to horizontally aligned MoS2 film. Vertically aligned MoS2 has superior resistance variation compared to horizontally aligned MoS2 even with same surface area exposed to identical concentration of gas molecules. We found that electrical response to target gas molecules correlates directly with the density of the exposed edge sites of MoS2 due to high adsorption of gas molecules onto edge sites of vertically aligned MoS2. Density functional theory (DFT) calculations corroborate the experimental results as stronger NO2 binding energies are computed for multiple configurations near the edge sites of MoS2, which verifies that electrical response to target gas molecules (NO2) correlates directly with the density of the exposed edge sites of MoS2 due to high adsorption of gas molecules onto edge sites of vertically aligned MoS2. We believe that this observation extends to other 20 TMD materials as well as MoS2 and can be applied to significantly enhance the gas sensor performance in these materials.
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