Sensitivity Enhancement of Metal Oxide Thin Film Transistor with Back Gate Biasing

In this work, a room-temperature sensing device for detecting carbon monoxide using a ZnO thin film is presented. The ZnO layer (thickness close to the Debye length), which has a polycrystalline structure, is deposited with atomic- layer deposition (ALD) on an Al2O3/Si substrate. The operating principle of the sensor is based on measuring resistance change of the ZnO thin film upon exposure to CO in ambient environment. The ZnO-based sensor shows a large response to low CO concentrations ranging from 5 to 25 ppm in air with 40% relative humidity at room temperature. Results show that the sensitivity of the sensor to CO at room temperature can be modulated with a back gate voltage.