Facile fabrication method and decent humidity sensing of anodised nanotubular Ta2O5 on Ta foil substrate

In this study, nanotubular structures were prepared on tantalum film via anodisation using an organic-based electrolyte. Nanotubular tantalum pentoxide (Ta2O5) was synthesised at 30 and 60 min and fabricated as a humidity sensor. The significant growth of anodised nanotubular Ta2O5 has increased the number of pore structures and offered more water absorption active sites for humidity sensing detection. Both anodised samples were annealed to transform an amorphous structure to a cubic crystal structure, where the presence of more crystalline peaks was justified by the XRD spectra. The formation of pore size was proven by FESEM images and the density of pore distribution of the 60-min sensor was higher than the 30-min sensor with a diameter of 10-50 nm and 15-20 nm, respectively. Both fabricated sensors were tested for humidity detection in the range of 40-90% humidity level. Based on the results obtained, the 60-min sensor operated at 10 V possessed the highest sensitivity, low hysteresis, and improved stability compared to the 30-min sensor operated at the same bias voltage. Thus, this paper has elucidated the relationship of anodising time during nanostructure construction towards the variation of current output in humidity sensing due to the availability of oxygen vacancies and active sites as an effort to improve humidity sensing.