| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 106 === In this work, we have successfully combined the glancing angle deposition (GLAD) approach with plasma-assisted chemical vapor reduction (PACVR) method to fabricate the nano-structured tungsten diselenide (WSe2) as the reactive layer for gas sensor application.
The purpose of using GLAD system is to obtain the nanostructures with much larger surface-area-to-volume ratio compared to flat films, thus increasing the capacity for sensing application. Here we choose WSe2 as the sensing material for nitric oxide (NO) gas detection due to its p-type semiconducting property and effective charge transfer with NO molecules. [1] After parameter optimization, our sensor shows the highly sensitive performance with a response over 40% at 60 ppb at room temperature, and a derived limit of detection about 15 ppb.
We also demonstrated that the composition of phases in the WSe2 will influence the sensing behavior, revealing the importance of small amount of 1T (metallic) phase existed in the dominant 2H (semiconducting) matrix to enhance the sensing capability, where the phase concentration can be controlled by the synthesis temperature during PACVR process.
Additionally, in comparison with conventional chemical vapor deposition (CVD) processes, the assistance of plasma function facilitates the transformation of transition metal dichalcogenides (TMDCs) at lower temperatures, showing the potential for flexible devices fabrication.
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