Affiliation: | 1. King Abdullah Institute for Nanotechnology, King Saud University, Riyadh, Saudi Arabia;2. National Solar Energy Technology Center, King Abdulaziz City of Science and Technology (KACST), Riyadh, Saudi Arabia;3. King Abdullah Institute for Nanotechnology, King Saud University, Riyadh, Saudi Arabia
Research Chair for Tribology, Surface and
Interface Sciences, Physics and Astronomy Department, College of Science, King Saud University, Riyadh, 11451 Saudi Arabia
ARAMCO Laboratory for Applied Sensing Research, King Abdullah Institute for Nanotechnology King Saud University, Riyadh, Saudi Arabia
Physics and Astronomy Department, College of Science, King Saud University, Riyadh, Saudi Arabia
National Center for Nanotechnology and Advanced Materials, King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia;4. Physics and Astronomy Department, College of Science, King Saud University, Riyadh, Saudi Arabia
National Center for Nanotechnology and Advanced Materials, King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia;5. National Center for Nanotechnology and Advanced Materials, King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia
Institute of Physical and Theoretical Chemistry (IPTC), University of Tuebingen, Tuebingen, Germany;6. Chemical Engineering Department, King Saud University, Riyadh, Saudi Arabia |
Abstract: | In this study, pulsed laser ablation technique, also known as pulsed laser deposition (PLD), is used to design and grow zinc oxide (ZnO) nanostructures (nanoworms, nanowalls, and nanorods) by template/seeding approach for gas-sensing applications. Conventionally, ZnO nanostructures used for gas-sensing have been usually prepared via chemical route, where the 3D/2D nanostructures are chemically synthesized and subsequently plated on an appropriate substrate. However, using pulsed laser ablation technique, the ZnO nanostructures are structurally designed and grown directly on a substrate using a two-step temperature-pressure seeding approach. This approach has been optimized to design various ZnO nanostructures by understanding the effect of substrate temperature in the 300-750°C range under O2 gas pressure from 10-mTorr to 10 Torr. Using a thin ZnO seed layer as template that is deposited first at substrate temperature of ~300°C at background oxygen pressure of 10 mTorr on Si(100), ZnO nanostructures, such as nanoworms, nanowalls, and nanorods (with secondary flower-like growth) were grown at substrate temperatures and oxygen background pressures of (550°C and 2 Torr), (550°C and 0.5 Torr), and (650°C and 2 Torr), respectively. The morphology and the optical properties of ZnO nanostructures were examined by Scanning Electron Microscope (SEM-EDX), X-ray Diffraction (XRD), and photoluminescence (PL). The PLD-grown ZnO nanostructures are single-crystals and are highly oriented in the c-axis. The vapor-solid (VS) model is proposed to be responsible for the growth of ZnO nanostructures by PLD process. Furthermore, the ZnO nanowall structure is a very promising nanostructure due to its very high surface-to-volume ratio. Although ZnO nanowalls have been grown by other methods for sensor application, to this date, only a very few ZnO nanowalls have been grown by PLD for this purpose. In this regard, ZnO nanowall structures are deposited by PLD on an Al2O3 test sensor and assessed for their responses to CO and ethanol gases at 50 ppm, where good responses were observed at 350 and 400°C, respectively. The PLD-grown ZnO nanostructures are very excellent materials for potential applications such as in dye-sensitized solar cells, perovskite solar cells and biological and gas sensors. |