Photocatalytic Titanium Dioxide Nanostructures for Self-Regenerating Relative Humidity Sensors

Relative humidity sensors with a nanostructured titanium dioxide sensing layer were fabricated using glancing angle deposition. Such sensors exhibit very quick response times and high sensitivity but are prone to aging. In previous work, ultraviolet irradiation has been shown to regenerate and improve the sensor performance. Here, the effect of ultraviolet wavelength and power on sensor performance, aging, and regeneration was studied. In order to quantify the change in sensor response a figure of merit (FOM) was defined as the integrated area between the sensor response curves before and after regeneration or aging. FOM values ranged from 2.1 to 61 for treatment with a mercury vapor lamp. Treated sensors aged at an average rate of -0.43 FOM/day. Regeneration of sensors using commercial ultraviolet light-emitting diodes was demonstrated, resulting in FOMs significantly larger than irradiation with comparable mercury vapor lamp wavelengths.