Phase-modulated 3D-hierarchical 1T/2H WSe2 nanoscrews by a plasma-assisted selenization process as high performance NO gas sensors with a ppb-level detection limit

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2019, Vol.7 (39), p.22314-22322
• Main Authors: Yu-Ze, Chen, Shao-Hsin, Lee, Teng-Yu, Su, Shu-Chi, Wu, Pin-Jung, Chen, Yu-Lun Chueh
• Format: Article
• Language: English
• Subjects: Charge transfer; Chemical bonds; Detection; Gas sensors; Heterojunctions; Hybrids; Low temperature; Nitric oxide; Organic chemistry; P-type semiconductors; Phases; Plasma; Sensors; Substrates
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c9ta05348d

In this work, we create plasma-engineered-1T/2H 3D-hierarchical WSe2 nanoscrews derived from WOx 3D-hierarchical nanoscrews through a low-temperature plasma-assisted selenization process with controlled shapes grown using a glancing angle deposition (GLAD) system. Through a detailed investigation of chemical bonding in WSe2 by XPS and TEM, it was found that hybrids of 1T and 2H phases can be engineered, depending on substrate temperatures under plasma treatment. The GLAD system was exploited to achieve 1D nanostructures to enhance the surface-area-to-volume ratio compared to that of flat films, thus increasing the capacity for sensing applications. Here, WSe2 was chosen as the best sensing material for nitric oxide (NO) gas detection because of its p-type semiconducting properties and effective charge transfer with NO molecules. The performance of WSe2 nanoscrew gas sensors which was closely associated with 1T–2H phases was investigated where the barrier height decreased by the heterojunction of 1T/2H phases in WSe2 exhibiting the best sensing capability at a ratio of 0.41 between 1T and 2H phases was found. The plasma-engineered-1T/2H WSe2 3D-hierarchical nanoscrews exhibited a highly sensitive performance with a response over 40% at 60 ppb at room temperature with a detection limit of approximately ∼15 ppb. Finally, ∼100% response in air using the plasma-engineered-1T/2H WSe2 3D-hierarchical nanoscrews was demonstrated, proving their potential for application as next-generation high-performance gas sensors.