Stress-engineered palladium nanowires for wide range (0.1%–3.9%) of H2 detection with high durability

• Published in: Nanoscale Vol. 11; no. 35; pp. 16317 - 16326
• Main Authors: Jae-Shin, Lee, Min-Ho, Seo, Choi, Kwang-Wook, Jae-Young, Yoo, Min-Seung, Jo, Jun-Bo, Yoon
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 21.09.2019
• Subjects: Beta phase; Computer simulation; Design specifications; Detection; Durability; Exposure; Gas sensors; High temperature effects; Nanowires; Palladium; Parameters; Phase transitions; Recovery time; Relative humidity; Response time; Scanning electron microscopy; Sensor arrays; Sensors; Stiction; Substrates
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c9nr01975h

Pd nanowire-based H2 sensors have attracted significant attention because of their superior sensing performance. However, when exposed to H2 concentrations of more than 2%, Pd experiences volume expansion over 10%, resulting in a significant amount of mechanical stress. Thus, exposure to such high H2 concentrations causes physical destruction of Pd nanowires, such as breaks and peel-offs, leading to severe difficulty in the reliable detection of H2 over a wide concentration range. Here, we proposed a structural approach to resolve this issue by introducing a partially anchored Pd nanowire (PA-PdNW) structure. In this configuration, most of the structure was air-suspended, leaving a small portion anchored to the substrate. Air-suspension enabled PA-PdNW to expand freely, thus relieving the mechanical stress; therefore, the Pd nanowires could withstand numerous exposures to high H2 concentrations. To demonstrate the PA-PdNW structure, we developed a nano-fabrication method based on conventional semiconductor processes and successfully manufactured H2 sensor devices with uniform, perfectly aligned PA-PdNW arrays stably air-suspended with designed gaps from the substrate. The fabricated sensors achieved reliable detection of H2 in the 0.1%–3.9% concentration range with a significant resistance change. In addition, compared with fully anchored Pd nanowire (FA-PdNW) sensors, the PA-PdNW sensors showed superior durability, and the nanowires retained their initial structures even after 300 exposures to high H2 concentrations. Furthermore, it was confirmed that the PA-PdNW sensor can stably operate even in extremely humid environments at 85% relative humidity.