Amorphous TiO(2) nanotube arrays for low-temperature oxygen sensors.

Titania nanotube arrays (TNTA) were synthesized on a titanium substrate using anodic oxidation in an electrolyte containing ammonium fluoride and evaluated for low-temperature oxygen sensing. Their sensing properties were tested at different temperatures (50, 100, 150, 200, 250 and 300 °C) when exposed to various oxygen concentrations. The as-prepared TNTA are amorphous and exhibit much higher carrier concentration than that of annealed TNTA. Such amorphous TNTA show much higher sensitivity than that of annealed TNTA, SrTiO(3) and Ga(2)O(3) sensors. This sample demonstrates the lowest detectable oxygen concentration of 200 ppm, excellent recovery and good linear correlation at 100 °C. These results indicate that TNTA are indeed very attractive oxygen-sensing materials.