Room temperature CO gas sensing using Zn-doped In₂O₃ single nanowire field effect transistors

We demonstrate a room temperature sensing of CO gas (1-5 ppm) using high performance single Zn-doped In₂O₃ nanowire field effect transistors (Zn-In₂O₃ NW-FETs). Zn-In₂O ₃ nanowires were grown in a horizontal CVD furnace; single Zn-In ₂O₃ NW-FETs were fabricated using SiN_x dielectric layer and bottom gate. Electrical measurements on the NW-FETs showed high performance devices, with a high "ON" current of 8 × 10^-6 A at a 5 V drain voltage, high on-off ratio of ∼10 ⁶ and electron mobility of 139 cm² V^-1 s ^-1. Sensing properties of CO gas were studied using these NW-FETs at room temperature. Doping of Zn²⁺ into the In₂O₃ NW enhances the sensor response compared to pure In₂O₃ nanowire. A good selectivity of CO gas over NO and NO₂ can also be achieved. The improved sensor response at room temperature is attributed to the defects created and a change in conductivity of the nanowire upon Zn-doping. Significant negative threshold voltage shift of -3.5 V was observed after exposure to a low concentration of CO gas at 5 ppm. This approach represents an important step towards the room temperature sensing of hazardous gas.