New Room Temperature Ammonia Gas Sensor Synthesized by a Tantalum Pentoxide (Ta2O5) Dielectric and Catalytic Platinum (Pt) Metals

A new room temperature (25 °C) ammonia gas sensor based on a metal-oxide-semiconductor (MOS) diode is reported. The device structure is synthesized by a sputtered tantalum pentoxide (Ta 2 O 5 ) dielectric, evaporated platinum nanoparticles (Pt NPs), and a Pt thin film on a GaN/AlGaN heterostructure. Pt NPs can effectively increase the specific surface area and related catalytic reactivity of Pt metal. In experiment, the studied Pt NP/Pt/Ta 2 O 5 /GaN/AlGaN MOS device shows good ammonia sensing properties including a high sensing response of 74.4 under 1000 ppm NH 3 /air gas and a sub-ppm (100 ppb) detecting level at room temperature. The studied MOS diode has the advantages of low power, low cost, and a widespread concentration range (0.1-1000 ppm NH 3 /air) for ammonia sensing operation. The ammonia sensing mechanism and a thermodynamic analysis to study the related interface coverage are included in this article. The studied MOS diode also exhibits advantages of good selectivity toward ammonia gas and a simple device structure.