Al Modified Orthorhombic Molybdenum Trioxide as NO2 Gas Sensor

The aim of this study is to prepare thick films of MoO3 with various weight percentages of aluminum dopant and study its gas sensing characteristics. The thick films were prepared on alumina substrate using easily reproducible, cost-effective screen printing method. The films were characterized using XRD, FESEM, EDS and static gas sensing apparatus. The XRD analysis confirmed the presence of Molybdenum trioxide (JCPDS 05-0508) and aluminum (JCPDS 31-0026). The XRD conveyed that aluminum has occupied an interstitial position and got oxidized to alumina. FESEM showcased the characteristic lamellar structure of MoO3 with voids. The EDS data showed that films were having oxygen excess and the oxygen vacancies increased with aluminum doping percentage. Resistivity and activation energies decreased first and then increased with dopant (aluminum) percentage. The Al-5 films showed a minimum resistivity (61.05 x 10(4) Omega m) and activation energy (0.19 eV). The TCR had a negative value for all five films supporting n-type semiconductor behavior of the films. The Al-5 films showed 84.3% sensitivity to 1000 ppm of NO2 gas at 200 degrees C. Authors discussed adsorption-desorption based gas sensing mechanism in detail. Research work tested efficient NO2 gas sensor using aluminum-doped MoO3 thick films.