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.
Highlights
As we continue to progress into the era of the Internet of Things, our lives will undergo significant change
We know that common Metal oxide semiconductor (MOS) are n-type semiconductors whose resistance may go beyond the detection limits of conventional circuitry when exposed to oxidative gases
This study indicates that p-type thin film gas sensors can be connected to the Internet of Things and used in a smart house safety system as well as for leakage detection during long-distance transport of liquefied petroleum gas (LPG)
Summary
As we continue to progress into the era of the Internet of Things, our lives will undergo significant change. Metal oxide semiconductor (MOS)-based gas sensors, whose resistance changes under different degrees of gas concentration, are currently widely used in industrial and domestic applications to detect the concentration and types of gas present. Many MOSs are appropriate for gas detection, such as tungsten trioxide (WO3) [36–39], tin oxide (SnO2) [40–42], and zinc oxide (ZnO) [43,44]. These gas sensors attract considerable attention because of their high sensitivity, flexibility in production, low cost, and suitability for detecting both reducing and oxidizing gases. We know that common MOSs are n-type semiconductors whose resistance may go beyond the detection limits of conventional circuitry when exposed to oxidative gases. P-type gas-sensing metal oxide semiconductors can overcome this limitation while preserving the advantages of these kind of semiconductors [45,46]
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