Enhanced UV-Sensing Performances of 2-D Pd/ZnO Nanosheet Photodetectors through Inexpensive Photochemical Synthesis at Room Temperature and Their Humidity Applications
Yen‐Lin Chu, Sheng‐Joue Young, Chien‐Hung Liu, Sandeep Arya, Tung-Te Chu
Abstract
A simple wet chemical solution method with an inexpensive photochemical synthesis process was performed to fabricate high-quality vertically aligned palladium nanoparticle (Pd NP)-decorated two-dimensional (2-D) zinc oxide (ZnO) nanosheets (NSs) on a seed layer/glass substrate at room temperature. The ultraviolet (UV) photodetectors (PDs) with and without decorated Pd NPs in this article were named PdZO@-1 and PdZO@-0 NSs, respectively. Field-emission scanning electron microscopy, X-ray diffraction, and high-resolution transmission electron microscopy measurement results showed that the 2-D nanostructures perpendicularly grew on the substrate, interwoven with one another, and oriented preferentially along the (002) plane with good polycrystalline crystallinity. The morphological images revealed that the average length and thickness of the 2-D PdZO@-0 NSs were 2.62 and 30.2 nm, whereas the average length and thickness of the 2-D PdZO@-1 NSs were 2.69 and 30.5 nm, respectively. The optical characteristics and chemical compositions of UV PDs were determined by photoluminescence (PL), UV–visible absorbance/transmittance, and X-ray photoelectron spectroscopy. Energy-dispersive X-ray determined that the PdZO@-1 NS samples contained approximately 1.12 at. % Pd element. At the applied bias of 1 V, the rise times under UV illumination of the PdZO@-0 and PdZO@-1 PDs were 200 and 49.3 s, respectively, with decay times of 126.6 and 23.6 s, respectively. The I ph / I dark ratios of the PdZO@-1 NS PDs (4882) were higher than those of the PdZO@-0 NS PDs (940). Additionally, the PdZO@-1 PDs also showed good electrical performance in a humid environment. The rise and decay times under 90% relative humidity (RH) were 13.3 and 2.9 s, respectively. Compared with that of the 2-D PdZO@-0 NSs, the specific detectivity rate significantly improved at a humidity of 30–90% for the 2-D PdZO@-1 NSs. Overall, the results exhibited that the 2-D PdZO@-1 NSs showed enhanced UV-sensing performances at different RH levels, and they are a promising candidate in future Internet of Things for UV PD-based devices with humidity control applications (e.g., cataract disease, skin aging, skin cancer, food safety, incubators, and biological products).