Highly Sensitive NO₂ Detection by TVS-Grown Multilayer MoS₂ Films

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Two-dimensional layered materials like MoS₂ are promising for sensors due to their large surface area and electrical properties.
• Grain boundaries in polycrystalline materials are often overlooked but can significantly impact device performance.
• Understanding grain boundary effects is crucial for optimizing sensors based on layered materials.

Purpose of the Study:

• To investigate the influence of grain size and grain boundaries on the NO₂ sensing properties of MoS₂ films.
• To compare MoS₂ films grown by chemical vapor deposition (CVD) and thermal vapor sulfurization (TVS) for sensor applications.
• To elucidate the mechanisms behind enhanced NO₂ adsorption and sensing in polycrystalline MoS₂.

Main Methods:

• Growth of MoS₂ films with varying grain sizes using CVD and TVS methods.
• Fabrication of transistor-based gas sensors using the synthesized MoS₂ films.
• Evaluation of NO₂ sensing performance, including sensitivity and adsorption behavior (Langmuir isotherm).
• Characterization using transmission electron microscopy (TEM) and theoretical calculations.

Main Results:

• CVD-grown MoS₂ films exhibited superior electrical properties due to larger grain sizes.
• TVS-grown MoS₂ films, with smaller grain sizes and mirror twin grain boundaries, showed unexpectedly higher NO₂ sensitivity.
• NO₂ adsorption on modeled grain boundaries was comparable to the ideal basal plane.
• Porous structures in TVS-grown films may also contribute to enhanced sensing.

Conclusions:

• Highly sensitive MoS₂ gas sensors can be fabricated using polycrystalline films with small grain sizes.
• Grain boundaries and porous structures play a significant role in enhancing NO₂ sensing.
• This research opens possibilities for optimizing sensors based on other two-dimensional materials by controlling grain characteristics.