Effects of rapid thermal annealing on the room-temperature NO₂-sensing properties of WO₃thin films under LED radiation

Abstract

WO3 thin films were sputtered onto alumina substrates by DC facing-target magnetron sputtering. One sample was rapid-thermal-annealed (RTA) at 600 °C in a gas mixture of N2:O2 = 4:1, and as a comparison, another was conventionally thermal-annealed at 600 °C in air. The morphology of both was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the crystallization structure and phase identification were characterized by X-ray diffraction (XRD). The NO2-sensing measurements were taken under LED light at room temperature. The sensitivity of the RTA-treated sample was found to be high, up to nearly 100, whereas the sensitivity of the conventionally thermal-annealed sample was about five under the same conditions. From the much better selectivity and response-recovery characteristics, it can be concluded that compared to conventional thermal annealing, RTA has a greater effect on the NO2-sensing properties of WO3 thin films.

Fast-Response Room Temperature Hydrogen Gas Sensors Using Platinum-Coated Spin-Capable Carbon Nanotubes

“…Consequently, there has been extensive research on sensing materials for gas detection that operate at lower temperatures. 6,7 Over the past decade, carbon nanotube (CNT)-based gas sensors have been extensively investigated for real-time chemical sensor applications in monitoring and detecting many gases of interest in environmental pollution, chemical processes, and medical fields. 8 Unlike classical semiconducting metal oxide gas sensors requiring high operating temperatures (>300 °C), CNT-based gas sensors are capable of room temperature detection of hazardous gases such as ammonia (NH 3 ) and nitrogen dioxide (NO 2 ).…”

“…This requires high power consumption and creates an elevated risk of explosion. Consequently, there has been extensive research on sensing materials for gas detection that operate at lower temperatures. , …”

Structures and optical properties of tungsten oxide thin films deposited by magnetron sputtering of WO 3 bulk: Effects of annealing temperatures

“…In the past few years, an increasing interest has been put on the tungsten oxide films due to their potential applications in smart windows, [1,2] gas sensors, [3,4] photocatalytic reactions, [5] and optoelectronic devices, [6] etc. The unique properties of the tungsten oxide films were usually determined by the oxygen defects and the valence states of tungsten ions.…”

“…As we all know, annealing, or thermal, treatment is one of the most effective ways to influence the structure and the properties of many films. [4,[27][28][29][30] The deposited films were annealed at 200 • C and 300 • C for 60min and at 400 • C for 60 min and 180 min in air, respectively. We find that the annealing temperature of 400 • C can effectively influence the structure and optical property of the deposited films.…”