Synthesis and optimum temperature determination of highly sensitive MoO3-based heterojunction Schottky sensor for hydrogen detection

Abstract

In this investigation, thin films of molybdenum trioxide (MoO3) were deposited on a silicon substrate using the physical vapor deposition method to fabricate a Pt/MoO3/Si heterojunction Schottky diode. To study the morphological characteristics, chemical composition and crystalline phases present in the synthesized thin films, FESEM, Raman spectroscopy, and XRD pattern analysis were performed, respectively. The XRD pattern proves the formation of an α-MoO3 phase structure. Raman spectra indicate that deposited films are orthorhombic and FESEM image of the sample demonstrates the uniformly growth of thin films. The platinum and gold metals were used as the electrodes to form Schottky and ohmic contacts of the gas sensor, respectively. The fabricated sample was exposed to 0.05% up to 0.25% concentrations of Hydrogen gas at 170 to 300 °C. It is observed that the highest sensitivity of the sensor occurs at 260 °C. The response values at an optimum temperature of 260 °C were about 18% for 0.05% and 58% for 0.25% of the target gas, while the sample exhibits response and recovery times of 29 and 158 s toward 0.25% of hydrogen gas, respectively. Moreover, the Schottky barrier height of the fabricated heterojunction diode is estimated to be 0.32 eV, which confirms its rectifying behavior.