Titanium-Doped P-Type WO3 Thin Films for Liquefied Petroleum Gas Detection

Abstract

Gas sensors are an important part of smart homes in the era of the Internet of Things. In this work, we studied Ti-doped P-type WO3 thin films for liquefied petroleum gas (LPG) sensors. Ti-doped tungsten oxide films were deposited on glass substrates by direct current reactive magnetron sputtering from a W-Ti alloy target at room temperature. After annealing at 450 °C in N2 ambient for 60 min, p-type Ti-doped WO3 was achieved for the first time. The measurement of the room temperature Hall-effect shows that the film has a resistivity of 5.223 × 103 Ωcm, a hole concentration of 9.227 × 1012 cm−3, and mobility of 1.295 × 102 cm2V−1s−1. X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses reveal that the substitution of W6+ with Ti4+ resulted in p-type conductance. The scanning electron microscope (SEM) images show that the films consist of densely packed nanoparticles. The transmittance of the p-type films is between 72% and 84% in the visible spectra and the optical bandgap is 3.28 eV. The resistance increased when the films were exposed to the reducing gas of liquefied petroleum gas, further confirming the p-type conduction of the films. The p-type films have a quick response and recovery behavior to LPG.