Au/TiO2 Nanotubes/Ti-Based Solid-State Vapor Sensor: Efficient Sensing in Resistive and Capacitive Modes

Fabrication of TiO₂ nanotubes-based solid-state vapor sensor (Au/TiO₂ nanotubes/Ti) and its performance analysis for both resistive- and capacitive-mode sensing mechanisms are discussed here. Highly ordered TiO₂ nanotubes array has been synthesized by the electrochemical anodization technique. Structure and morphology of the as-grown TiO₂ nanotubes have been characterized using X-ray diffraction and field-emission scanning electron microscopy. X-ray photoelectron spectroscopy has been used to study the chemical states of the TiO₂ nanotubes. The sensor device has successfully been tested for ethanol vapor. The effect of temperature, pressure, and reducing ambient (i.e., partial pressure of ethanol vapor) has been studied using the impedance analysis method. The resistive and capacitive components of the impedance were measured individually. The sensor resistance decreased by 93.38%, whereas the capacitance increased by 28789.95% after an exposure to 1000 ppm of ethanol. Both the resistive and capacitive sensing performance of Au/TiO₂ nanotubes/Ti device have been correlated with the proposed circuit model to achieve an improvised vapor sensing.