Carbon nanotubes(CNT) has chemical stability and great sensitivity characteristics. In particular, the gassensor required characteristics such as rapid, selectivity and sensitivity sensor. Therefore, CNT are ideal materialsto gas sensor. So, we fabricated the NOx gas sensors of MOS-FET type using the MWCNT (multi-walled carbonnanotube). The fabricated sensor was used to detect the NOx gas for the variation of Vgs (gate-source voltage)and electrode changed electrode spacing=30, 60, 90[㎛]. The gas sensor absorbed with the NOx gas moleculesshowed the decrease of resistance, and the sensitivity of sensor was increased by magnification of electrodespacing. Furthermore, when the voltage(Vgs) was applied to the gas sensor, the decrease in resistance wasincreased. On the other hand, the sensor sensitivity for the injection of NOx gas was the highest value at theelectrode spacing 90[㎛]. We also obtained the adsorption energy(Vgs) using the Arrhenius plots by the reduction ofresistance due to the voltage variations. As a result, we obtained that the adsorption energy was increased withthe increment of the applied voltages.

Carbon nanotubes (CNT) has the excellent physical characteristics in the sensor, medicine, manufacturing and energy fields, and it has been studied in those fields for the several years. We fabricated the NOx gas sensors of MOS-FET type using the MWCNT. The fabricated sensor was used to detect the NOx gas for the variation of Vgs (gate-source voltage) with the ambient temperature. The gas sensor absorbed the NOx gas molecules showed the decrease of resistance, and the sensitivity of sensor was reduced by the NOx gas molecules accumulated on the MWCNT surface. Furthermore, when the voltage (Vgs) was applied to the gas sensor, the term of the decrease in resistance was increased. On the other hand, the sensor sensitivity for the injection of NOx gas was the highest value at the ambient temperature of 40℃. We also obtained the adsorption energy (Vgs)using the Arrhenius plots by the reduction of resistance due to the Vgs voltage variations. As a result, we obtained that the adsorption energy also was increased with the increasement of the applied Vgs voltages.

Carbon nanotubes(CNT) has strength and chemical stability, greatly conductivity characteristics. In particular, MWCNT (multi-walled carbon nanotubes) show rapidly resistance sensitive for changes in the ambient gas, and therefore they are ideal materials to gas sensor. So, we fabricated NOx gas sensors structured MOS-FET using MWCNT (multi-walled carbon nanotubes) material. We investigate the change resistance of NOx gas sensors based on MOS-FET with ultra lean NOx gas concentrations absorption. And NOx gas sensors show sensitivity on the change of gate-source voltage (V98 =0[V] or V98=3.5[V]). The gas sensors show the increase of sensitivity with increasing the temperature (largest value at 40℃). On the other hand, the sensitivity of sensors decreased with increasing of NOx gas concentration. In addition, We obtained the adsorption energy(Ua), Ua = 0.06714[eV] at the NOx gas concentration of 8[ppm], Ua = 0.06769[eV] at 16[ppm], Ua = 0.06847[eV] at 24[ppm] and Ua = 0.06842[eV] at 32[ppm], of NOx gas molecules concentration on the MWCNT gas sensors surface with using the Arrhenius plots. As a result, the saturation phenomena is occurred by NOx gas injection of concentration for 32[ppm].

Carbon nanotubes(CNT) have excellent electrical, chemical stability and mechanical properties. These can be used in a variety of fields. MWCNT are extremely sensitive for minute changes in the ambient gas, namely, their sensing properties varies greatly with the absorption of gas such as NOx and H2. We investigate the electrical properties of CNTs and make a NOx gas sensor based on Multi-walled carbon nanotubes (MWCNT) materials. We obtained the NOx gas sensor of MWCNT based on P-type Si wafer that has the resistivity of 1.667×10-1 [Ω·cm]. We knew that the sensitivity of sensor decreased with increasing of NOx gas concentration. And the sensitivity of sensor shows the largest value at 20℃. The sensitivity of sensor decrease with increasing the temperature. Also absorption energy of NOx gas molecule on the MWCNT surface decreases with increasing concentration of NOx gas.

Carbon nanotubes (CNTs) have excellent electrical, chemical stability, mechanical and thermal properties. In this paper, networks of Multi-walled carbon nanotube (MWCNT) materials were investigated as a resistive gas sensors for the H2 gas detection. Sensor films were fabricated by the air spray method using the multi-walled CNTs dispersion solution on the glass substrates cured with plasma and nitrocellulose. Sensors were characterized by the resistance measurements in the self-fabricated oven in order to find the optimum detection properties for the hydrogen gas molecular. The sensitivity and the linearity of the MWVNT sensors using the glass substrate cured with plasma for the H2 gas concentration of 0.06∼0.6 ppm are 0.013∼0.097%/sec and 0.131∼0.959%FS, respectively. The MWCNT film was excellent in the response for the hydrogen gas moleculars and its reaction speed was very fast, which could be using as hydrogen gas sensor. The resistance of the fabricated sensors decreases when the sensors are exposed to H2 gas.