## 3 Results and Discussion  
First, the responses of the TFT-based humidity sensors fabricated using the MoS\({}_{2}\) thin film synthesized via the hydrothermal and CVD synthesis methods were compared. For comparison, the humidity in the range of approximately 40-60% was measured using a commercial capacitance-type sensor (TR-72 WB). Because a capacitor-type sensor was used as a reference to measure the humidity variation, it was difficult to change the humidity quickly. As shown in Figure 3, the currents in both sensors increased with increasing humidity. Generally, when water vapors are adsorbed, superoxides (O\({}^{2-}\)) dominate the dissociation of water molecules at room temperature. The resulting OH\({}^{-}\) is chemically adsorbed onto MoS\({}_{2}\), serving as an electron donor and increasing the conductivity of the n-type MoS\({}_{2}\) semiconductor, leading to an increase in the current [26,27]. The sensor using hydrothermally synthesized MoS\({}_{2}\) exhibited a fast response to water vapor absorption but a slow recovery time, as shown in Figure 3a. Although the fabricated sensor showed a relatively faster recovery rate compared to the commercial sensor, it was not able to achieve a sufficiently high recovery rate to observe breathing. Similar results have been reported previously [23]. To evaluate the applicability of MoS\({}_{2}\) as a respiration sensor, it is essential to determine whether the problem lies in the moisture absorption of the MoS\({}_{2}\) film itself or if there are other external factors at work. The current response of the humidity sensor fabricated using MoS\({}_{2}\) synthesized via CVD, as compared to that fabricated with hydrothermally synthesized MoS\({}_{2}\), increased as the humidity increased from 40% to 55%. As shown in Figure 3b, the sensor fabricated  
Figure 3: Current response depending on the humidity change for samples synthesized via (**a**) the hydrothermal method and (**b**) CVD. using MoS\({}_{2}\) synthesized via CVD exhibited much faster response and recovery rates than the conventional sensor fabricated using hydrothermally synthesized MoS\({}_{2}\). This indicates that the fabricated sensor was highly sensitive to changes in humidity. However, these results differ from those of previously reported studies on sensors with a slow recovery time [23]. Therefore, the differences in the response and recovery rates between humidity sensors fabricated using MoS\({}_{2}\) synthesized via CVD and those fabricated hydrothermal method were examined. In the hydrothermal method, the mechanism underlying the formation of MoS\({}_{2}\) is associated with the anion exchange and reduction reactions described by the following equations [28]:  
\[\text{CH}_{3}\text{CSNH}_{2}+4\text{H}_{2}\text{O}\rightarrow\text{H}_{2}\text{ S}+\text{NH}_{3}+2\text{CO}_{2}+4\text{H}_{2} \tag{1}\]  
\[\text{H}_{2}\text{S}+\text{OH}^{-}\rightarrow\text{S}^{2-} \tag{2}\]  
\[\text{MoO}_{3}+\text{S}^{2-}\rightarrow\text{MoO}_{3}\text{ (intermediate)}\rightarrow\text{(1T/2H) MoS}_{2} \tag{3}\]  
At first, CH\({}_{3}\)CSNH\({}_{2}\) is decomposed to produce S\({}^{2-}\) anions through the hydrolyzation steps. Then, MoS\({}_{2}\) (intermediate) is formed through a direct anion exchange reaction between the O\({}^{2-}\) anion of MoO\({}_{3}\) and S\({}^{2-}\) anions of sulfur. Finally, MoS\({}_{3}\) is reduced to the 1T and 2H phases of MoS\({}_{2}\) as the final product. In the CVD method, the mechanism underlying the formation of MoS\({}_{2}\) can be described by the following equations [29]:  
\[\text{Mo (metal)}+\text{S (gas)}\rightarrow\text{MoS}_{2} \tag{4}\]  
The growth of the continuous MoS\({}_{2}\) thin films includes three major steps:  
1. The reaction of Mo and S to form the MoS\({}_{2}\) nuclei on the surface;
2. MoS\({}_{2}\) growth on the substrate, which is controlled by kinetic factors (e.g., temperature, pressure, and the growth time);
3. The coalescence of adjacent MoS\({}_{2}\) domains that merge into a continuous film.