Fast detection and low power hydrogen sensor using edge-oriented vertically aligned 3-D network of MoS2 flakes at room temperature

• Published in: Applied physics letters 2017-08, Vol.111 (9)
• Main Authors: Agrawal, A. V., Kumar, R., Venkatesan, S., Zakhidov, A., Zhu, Z., Bao, Jiming, Kumar, Mahesh, Kumar, Mukesh
• Format: Article
• Language: English
• Subjects: Adsorption; Alignment; Applied physics; Chemical sensors; Detection; Flakes; Gas sensors; Hybrid structures; Hydrogen; Molybdenum disulfide; Raman spectroscopy; Room temperature; Scanning electron microscopy; Sensors; Silicon dioxide; Silicon substrates; Spectrum analysis; Zinc oxide
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.5000825

The increased usage of hydrogen as a next generation clean fuel strongly demands the parallel development of room temperature and low power hydrogen sensors for their safety operation. In this work, we report strong evidence for preferential hydrogen adsorption at edge-sites in an edge oriented vertically aligned 3-D network of MoS2 flakes at room temperature. The vertically aligned edge-oriented MoS2 flakes were synthesised by a modified CVD process on a SiO2/Si substrate and confirmed by Scanning Electron Microscopy. Raman spectroscopy and PL spectroscopy reveal the signature of few-layer MoS2 flakes in the sample. The sensor's performance was tested from room temperature to 150 °C for 1% hydrogen concentration. The device shows a fast response of 14.3 s even at room temperature. The sensitivity of the device strongly depends on temperature and increases from ∼1% to ∼11% as temperature increases. A detail hydrogen sensing mechanism was proposed based on the preferential hydrogen adsorption at MoS2 edge sites. The proposed gas sensing mechanism was verified by depositing ∼2–3 nm of ZnO on top of the MoS2 flakes that partially passivated the edge sites. We found a decrease in the relative response of MoS2-ZnO hybrid structures. This study provides a strong experimental evidence for the role of MoS2 edge-sites in the fast hydrogen sensing and a step closer towards room temperature, low power (0.3 mW), hydrogen sensor development.