Improving the performance of anodized TA2O5 humidity sensors through surface modification with gold nanoparticles

Abstract

Nanostructured metal oxides have been widely employed in electronic devices as a sensing layer. The sensitivity of the sensor and its response time are among the main concerns in sensor fabrication. Due to this issue, this paper has introduced a doping mechanism that involves anodized Tantalum Pentoxide (Ta2O5) nanotubes to be incorporated with gold nanoparticles (AuNP). The introduction of a dopant into the substrate can improve the sensor functionality. Anodization was employed to synthesis Ta2O5 while AuNP was synthesized by citrate reduction method at five molarity. Different molarities of AuNP (0.12 mM to 0.63 mM) were doped into the Ta2O5 nanotubes to act as a catalyst and enhance the functionality of the humidity sensor. Physical and chemical properties of anodized Ta2O5-AuNP were justified using FESEM, XRD, EDX, AFM, TEM and UV–VIS analysis. All fabricated sensors were tested for humidity detection in the range of 40–90% humidity level to evaluate their response time, repeatability, and sensitivity. According to the characterization results, 0.25 mM gold nanoparticles cause the Ta2O5 nanotube-based humidity sensor to produce the best performance. This is expected to occur because the optimum distribution of gold nanoparticles present on the Ta2O5 surface enhances the chemisorption and physisorption process which shorter the response and recovery time of the humidity sensor operation. Ta2O5 doped with 0.25 mM AuNP produced a sensitivity of 39.85 nA/%RH. However, doping beyond 0.25 mM of AuNP results in heavily doped conditions which lead to early failure of the device due to the metallic characteristic possessed by the sensor that degrades the sensor function and weakens the crystal structure.