## 4 Results and Discussion
### The Influence of Temperature on MoS\({}_{2}\) Growth
At a set temperature of 1073 K, the substrate temperature increases to 915 K, with a temperature difference of 158 K.  
Figure S5 present the velocity distribution and the cross-sectional velocity distribution at the center of the substrate under different set temperatures. Since the gas is in a laminar flow state, the flow velocity is higher at the center of the chamber. At a set temperature of 1033 K, the gas velocity at the inlet reaches a maximum of approximately 4.6 m/s. After entering the chamber, the velocity quickly decreases, with the flow velocity at the rear of the first temperature zone dropping to 0.03 m/s. When the gas transitions from the low-temperature zone to the high-temperature zone, the velocity increases rapidly, reaching 0.07 m/s at the center. This is due to the reduced gas density caused by the higher \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Source** & **Pressure** & **Temperature** & **Mo\({}_{3}\)O\({}_{9}\) Flow** \\ \hline \multirow{3}{*}{MoO\({}_{3}\) powder} & & 1033 K & 1.9 \(\times\) 10\({}^{-4}\) mol min\({}^{-1}\) cm\({}^{-2}\) \\  & 70 Torr & 1053 K & 3.9 \(\times\) 10\({}^{-4}\) mol min\({}^{-1}\) cm\({}^{-2}\) \\ \cline{1-1}  & & 1073 K & 6.6 \(\times\) 10\({}^{-4}\) mol min\({}^{-1}\) cm\({}^{-2}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Relationship between the evaporation rate of Mo\({}_{3}\)O\({}_{9}\) and temperature. Figure 2: Optical micrographs of the sample surface grown at (**a**) 1033 K, (**b**) 1053 K, and (**c**) 1073 K under a constant pressure of 70 Torr, along with the corresponding (**d**) Raman spectra and (**e**) PL spectra. temperature. However, it is noteworthy that as the set temperature increases, the change in gas velocity is minimal. Inside the crucible, the maximum gas velocity at the center is only about 0.001 m/s. Moreover, since the gas is in laminar flow, the gas velocity at the surface of the substrate is nearly zero, which helps create a relatively stable growth environment. This reduces the interference of the carrier gas on the nucleation and growth processes. The distribution of the flow field and temperature field determines the convective and diffusive rates of S\({}_{2}\) and Mo\({}_{3}\)O\({}_{9}\), which in turn influences their concentration distribution after evaporation. Under different growth temperatures, the concentration distribution of S\({}_{2}\) is shown in Figure S6. In the heated evaporation region, S\({}_{2}\) exhibits an uneven concentration distribution. Upon entering the high-temperature zone, the concentration of S\({}_{2}\) becomes uniformly distributed due to the high diffusion rate induced by the elevated temperature, reaching approximately 2.60 mol/m\({}^{3}\). As S\({}_{2}\) reaches the precursor MoO\({}_{3}\), it begins to react with the gaseous precursor Mo\({}_{3}\)O\({}_{9}\) and intermediate products, leading to a decrease in S\({}_{2}\) concentration. At growth temperatures of 1033 K, 1053 K, and 1073 K, the concentrations of S\({}_{2}\) at the substrate position are 1.32, 0.40, and 0.48 mol/m\({}^{3}\), respectively. The increase in temperature leads to a rise in the evaporation rate of Mo\({}_{3}\)O\({}_{9}\), which causes its concentration to increase inside the crucible, primarily concentrated above the precursor, as shown in Figure 3. At growth temperatures of 1033 K and 1053 K, the concentration of Mo\({}_{3}\)O\({}_{9}\) at the substrate position is 0 mol/m\({}^{3}\), indicating that the reaction between Mo\({}_{3}\)O\({}_{9}\) and S\({}_{2}\) is completed rapidly. However, when the growth temperature is increased to 1073 K, the concentration of Mo\({}_{3}\)O\({}_{9}\) at the substrate position rises to 0.03 mol/m\({}^{3}\).