INFLUENCE OF ANATASE TITANIUM DIOXIDE NANOTUBE ARRAYS ON HUMIDITY SENSOR SYNTHESIZED BY ELECTROCHEMICAL ANODIZATION

Abstract

Humidity sensors have become increasingly important and widely used to improve the quality of life and industrial processes. Over the past decades, titanium dioxide (TiO₂) has received wide attention in many promising areas such as sensors, solar cells, and photocatalytic. However, TiO₂ required high operating conditions such as high temperatures to examine the crystalline stability phase. This study focuses on highly ordered titanium dioxide nanotube arrays (TiO₂ NTAs) film synthesized using the electrochemical anodization method. Annealing temperature effect on the fabricated TiO₂ NTAs was investigated. An electrolyte solution was prepared by mixing ammonium fluoride (0.3 wt%) and ethylene glycol (25 ml) with deionized water (2 vol%). Titanium (Ti) sheet was anodized at 35 V for 120 minutes.  The films were annealed from 350 °C to 550 °C. FESEM images showed the diameter size of TiO₂ NTAs film decreases as the annealing temperatures increases. Results had also shown that the average diameter annealed at 450 °C was around ~50.82 nm while the XRD pattern demonstrated TiO₂ NTAs exhibiting an anatase phase with a prominent (101) peak recorded for the sample prepared at 450 °C with a high crystallite size of 29.17 nm. The calculated optical band gap annealed at 450 °C (3.24 eV) is comparable with other literature. The current-voltage characteristic of TiO₂ NTAs film reported a high current for 450 °C (1.12 x 10^-5 A) with a conductivity of 0.048 S.cm^-1 and high sensitivity (287.72).