Atomic-level mediation in structural interparameter tradeoff of zinc oxide nanowires-based gas sensors: ZnO nanofilm/ZnO nanowire homojunction array

• Published in: Applied surface science 2021-02, Vol.540, p.148350, Article 148350
• Main Authors: Jeon, In Su, Bae, Garam, Jang, Moonjeong, Yoon, Yeoheung, Jang, Seunghun, Song, Wooseok, Myung, Sung, Lim, Jongsun, Lee, Sun Sook, Jung, Ha-Kyun, Hwang, Jinha, An, Ki-Seok
• Format: Article
• Language: English
• Subjects: Atomic layer deposition; Gas response; Oxygen vacancy; Surface area; ZnO nanowires
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2020.148350

[Display omitted] •We presented a strategy to manipulate structural interparameter of ZnO nanofilm/ZnO nanowire.•The surface area and density of oxygen vacancies can be controlled by altering the ZnO nanofilms.•The gas response values ({(Ra-Rg)/Ra} × 100) were 84.2% (NO2), 45.9% (NH3), 35.8% (CH4), 29.2% (H2), and 31.2% (C3H8).•The oxygen vacancies in ZnO was more critical than its surface area in enhancing the gas response. The gas response of metal oxide-based gas sensors is determined by atomic scale defects associated with oxygen vacancies and surface area of the sensing element. In this study, we corroborated a facile strategy to manipulate the surface area and the density of oxygen vacancies (OVs) of ZnO nanowires (NWs) simultaneously using atomic layer deposition (ALD)-assisted conformal coating of homogeneous, thickness-tailored ZnO nanofilms. A comprehensive exploration of structural and chemical features of ZnO nanofilms/ZnO NWs homojunction reveals that the surface area and density of OVs can be manipulated by altering the thickness of the ZnO nanofilms. Resistive-type semiconductor gas sensors were fabricated on the thickness-tailored ZnO nanofilms/ZnO NWs homojunction. As a consequence, the optimized gas response values of the ZnO nanofilms/ZnO NWs formed by 50 ALD cycles were estimated to be 84.2% (20 ppm NO2), 45.9% (20 ppm NH3), 35.8% (2% CH4), 29.2% (100 ppm H2), and 31.2% (2% C3H8). The gas detection limit corresponded to 2 ppm for NO2, 2 ppm for NH3, 10 ppm for H2, 0.2% for CH4, and 0.2% for C3H8. In addition, we ascertained that the surface area was a critical factor for enhancing the gas response up to 50 ALD cycles, whereas the density of OVs was more critical than the surface area for gas sensing performance with increasing the ALD cycles (>50 cycles).