## 3 Results and Discussion
The binding energies of 1T MoS\({}_{2}\) and 2H MoS\({}_{2}\) are different, as observed via DFT modeling, which causes the adsorption rate, sensitivity, and desorption rate of the gas to change. Therefore, the improved sensitivity of the humidity sensor fabricated using CVD-synthesized MoS\({}_{2}\) can be attributed to its 2H crystal phase. In addition, the rate and strength of the adsorption and desorption of water can vary depending on the crystal phase change. For further verification, XPS (X-ray photoelectroscopy) was used to analyze different phase compositions of MoS\({}_{2}\). Figure 5 shows the Mo 3d and S 2p peaks of the XPS spectra of the CVD and hydrothermally synthesized MoS\({}_{2}\). For the CVD-synthesized MoS\({}_{2}\), two distinct peaks are found at 232.6 eV and 229.4 eV, corresponding to 3d\({}_{3/2}\) and 3d\({}_{5/2}\) of Mo\({}^{4+}\), thus indicating the presence of the 2H phase in MoS\({}_{2}\). Additionally, the weak peak at 226.5 eV is the S 2s of MoS\({}_{2}\). The new peaks that appear at around 235.5 eV for Mo 3d and 169 eV for S 2p regions can be attributed to the partial oxidation of unsaturated Mo and S atoms in the air. These results indicate that the 2H structure of MoS\({}_{2}\) was successfully synthesized with the CVD method. Figure 4: (**a**) Microscopic image, (**b**) SEM image, and (**c**) Raman spectrum of MoS\({}_{2}\) synthesized using the hydrothermal method. (**d**) Microscopic image, (**e**) SEM image, and (**f**) Raman spectrum of MoS\({}_{2}\) synthesized using the CVD method. As shown in Figure 5a, for the hydrothermally synthesized sample, the 3d\({}_{3/2}\) and 3d\({}_{5/2}\) peaks are shown to be 231.4 and 228.4 eV, respectively. These values are lower than those of the Mo\({}^{4+}\) peak of the 2H MoS\({}_{2}\). Hydrothermal synthesis generates more S defects than 2H crystal MoS\({}_{2}\). Additionally, it can be seen that the S 2s peak is lower than the 3d\({}_{3/2}\) and 3d\({}_{5/2}\) peaks. In addition, in the case of the S peak, the S 2P peak also shows that the binding energy of the hydrothermally synthesized MoS\({}_{2}\) is smaller than that of the CVD-synthesized MoS\({}_{2}\). It can be seen that the half-width value is large for the hydrothermally synthesized MoS\({}_{2}\). This indirectly indicates that a thin film with many defects, such as S defects, was formed. These defects impede the bonding of Mo and S ions, thus lowering the bonding energy. These results are consistent with the previously reported results. In addition, the results are consistent with the results of the prior to Raman analysis. The fabrication of a respiratory sensor using MoS\({}_{2}\) grown via the hydrothermal method was challenging owing to the desorption of the synthesized MoS\({}_{2}\) because of the slow response. A respiration sensor using a hydrothermally synthesized MoS\({}_{2}\) thin film has a response time of several tens of seconds, making it impossible to obtain a quick response. Therefore, a respiration sensor was fabricated using only MoS\({}_{2}\) synthesized via CVD. A humidity sensor was installed on the mask, as shown in Figure 6, to measure the response to respiration, and tests were carried out under various conditions. To determine whether the sensor responded sensitively to changes in humidity, the current response was examined as the humidity increased in various humidity environments. For the experiment on the humidity change, the manufactured sensor was loaded into a commercial humidity chamber, and the current was measured while changing the humidity. In order to observe the resistance change of the MoS\({}_{2}\) thin film placed between the two electrodes, the current response was analyzed while the voltage was varied from 0 to 5 V. As the relative humidity increased to 45-75%, the current significantly, linearly increased, indicating that it had the tendency to respond sensitively to changes in the amount of water vapor emitted during respiration.