## 3 Results and Discussion
In general, since CVD is synthesized at a high temperature of 500 degrees or more, it is common to obtain a 2H crystal structure. Thus, we believe that there are differences in the crystal phase of MoS\({}_{2}\) depending on the synthesis method. We attempted to analyze the differences in the crystal phase and their effect on the humidity response. First, we analyzed the crystal characteristics of films grown using different growth methods. Figure 4a,b shows the optical microscopy and SEM images of the hydrothermally synthesized MoS\({}_{2}\). As shown in Figure 4, the hydrothermally synthesized MoS\({}_{2}\) formed a thin film with micro-sized particles dispersed in a plane. In contrast, the optical microscopy (Figure 4d) and SEM images (Figure 4e) of the MoS\({}_{2}\) synthesized via CVD show that the MoS\({}_{2}\) grew well into a thin, nanometer-thick film in the patterned area. Although the shapes of thew MoS\({}_{2}\) synthesized via the two methods were different, Raman analysis confirmed that the MoS\({}_{2}\) thin film was well-formed. As shown in Figure 4c,f, E\({}^{1}\)\({}_{2\text{g}}\) and A\({}_{1\text{g}}\), which are the characteristic peaks of MoS\({}_{2}\), occurred in both samples. This shows that the MoS\({}_{2}\) thin films were well-formed using both synthesis methods. The E\({}^{1}\)\({}_{2\text{g}}\) mode is the horizontal vibration peak of Mo and S, whereas the A\({}_{1\text{g}}\) mode is the vertical vibration peak of sulfur. As the thickness increased, the E\({}^{1}\)\({}_{2\text{g}}\) peak shifted to a lower frequency because of the van der Waals forces between the layers, which caused the vibration direction to be perpendicular to the bonding force, whereas the A\({}_{1\text{g}}\) peak shifted to a higher frequency because the vibration direction was consistent with the bonding force. The layer number of MoS\({}_{2}\) can be predicted from the interval between the E\({}^{1}\)\({}_{2\text{g}}\) and A\({}_{1\text{g}}\) peaks. A narrow peak interval indicates single-layer MoS\({}_{2}\), which shows a peak interval of approximately 21 cm\({}^{-1}\). A wider peak interval indicates bulk MoS\({}_{2}\). As shown in Figure 4, Raman analysis of the MoS\({}_{2}\) grown via the sequential synthesis and CVD methods showed that the MoS\({}_{2}\) grown using the hydrothermal method had an E mode of approximately 382.1 cm\({}^{-1}\) and an A\({}_{1\text{g}}\) mode of approximately 408.3 cm\({}^{-1}\), with a peak interval of approximately 26 cm\({}^{-1}\), indicating that the MoS\({}_{2}\) grew with a thickness of three or more layers. In contrast, the Raman analysis results of the MoS\({}_{2}\) grown using the CVD method showed an E\({}^{1}\)\({}_{2\text{g}}\) mode at approximately 384 cm\({}^{-1}\) and an A\({}_{1\text{g}}\) mode at approximately 405 cm\({}^{-1}\), with a peak interval of 21 cm\({}^{-1}\), indicating that the MoS\({}_{2}\) grew with a thickness between that of the monolayer and bilayer. Although variations in the desorption and absorption of water vapor might exist due to differences in thickness, we focused on different points. As shown in Figure 4c,f, a unique peak occurred at \(\sim\)200 cm\({}^{-1}\) in the hydrothermally synthesized sample among the MoS\({}_{2}\) thin films grown using the two growth methods. This change in the Raman peak is due to the structural change in the material itself, and it has a shape that matches that of the 1T-phase molybdenum disulfide [30]. In the hydrothermal method, the 2H structure is destabilized by a second solvent-thermal reaction during sequential synthesis, and to improve the stability, to a certain extent, it is transformed into a 1T structure. Therefore, the optimal structure in which the 2H and 1T phases coexisted is ultimately formed [31]. Consequently, the hydrothermally synthesized MoS\({}_{2}\) develops a 1T@2H structure, and the CVD-synthesized MoS\({}_{2}\) develops a 2H structure. [PERSON] reported that the crystal phase is important for the gas-sensing performance [25].