High Surface Area to Volume Ratio 3D Nanoporous Nb2O5 for Enhanced Humidity Sensing

• Published in: Journal of Electronic Materials
• Main Author: Abdul Rani R.; Zoolfakar A.S.; Mohamad Ryeeshyam M.F.; Ismail A.S.; Mamat M.H.; Alrokayan S.; Khan H.; Kalantar-zadeh K.; Mahmood M.R.
• Format: Article
• Language: English
• Published: Springer New York LLC 2019
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071501039&doi=10.1007%2fs11664-019-07126-5&partnerID=40&md5=8f69c2dc7cd83f2fbb624abe0f6af23c

Sensors based on metal oxide platforms offer ease of device fabrication and simple sensing operation. As a metal oxide platform, highly nanoporous niobium oxide (Nb2O5) films consisting of unique three-dimensional vein-like structures can be efficiently used for developing humidity sensors. In this work, nanoporous Nb2O5 films (with different thicknesses of ∼ 1 μm, ∼ 2 μm, and ∼ 4 μm) were prepared by anodization of niobium foil for 30 min, 60 min, and 120 min. Electron, x-ray, atomic, and vibrational microscopies and spectroscopies were used for characterizing the morphological and structural properties of the Nb2O5 films. The analysis revealed that the nanoporous Nb2O5 exhibited hierarchical vein-like structures with orthorhombic crystalline orientation, and their surface roughness showed a proportional increase with the anodization duration. Metal–semiconductor–metal humidity sensors based on nanoporous Nb2O5 with platinum electrodes were tested in a humidity chamber under conditions of 40% to 90% relative humidity (RH) and different bias voltages. According to the obtained results, the ∼ 4-μm-thick nanoporous Nb2O5 presented the highest relative sensitivity of 216.5 under a bias voltage of 5 V, taking advantage of its extremely porous structure. These sensors provide high surface area to volume ratio, leading to highly effective affinity and interactions between surface-active sites and water molecules. © 2019, The Minerals, Metals & Materials Society.