In particular, gas sensors require characteristics such as high speed, sensitivity, and selectivity. In this study, we fabricated a NO_X gas sensor by using a multi-walled carbon nanotube (MWCNT)/zinc oxide (ZnO) composite film. The fabricated MWCNT/ZnO gas sensor was then treated by a 450℃ temperature process to increase its detection sensitivity for NOx gas. We compared the detection characteristics of a ZnO film gas sensor, MWCNT film gas sensor, and the MWCNT/ZnO composited film gas sensor with and without the heat-treatment process. The fabricated gas sensors were used to detect NO_X gas at different concentrations. The gas sensor absorbed NO_X gas molecules, exhibiting increased sensitivity. The sensitivity of the gas sensor was increased by increasing the gas concentration. Additionally, while changing the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we obtained its sensitivity for detecting NO_X gas. Compared with ZnO, the MWCNT film gas sensor is excellent for detecting NO_X gas. From the experimental results, we confirmed the enhanced gas sensor sensing mechanism. The increased effect by electronic interaction between the MWCNT and ZnO films contributes to the improved sensor performance.

The conduction behavior and electron concentration change in a-IGZO thin-films according to the RTA (rapid thermal annealing) were studied. The electrical characteristics of TFTs (thin-film-transistors) annealed by different temperatures were measured. The sheet resistance, electron concentration, and oxygen vacancy of a-IGZO film were measured by the four-point-probe-measurement, hall-effect-measurement, and XPS analysis. The RTA process increased the driving current of IGZO TFTs but the VTH shifted to the negative direction at the same time. When the RTA temperature is higher than 250℃, the leakage current at off-state increased significantly. This is attributed to the increase of oxygen vacancy resulting in the increase of electron concentration. We demonstrate that the RTA is a promising process to adjust the VTH of TFT because the RTA process can easily modify the electron concentration and control the conductivity of IGZO film with short process time.