## 4 Results and Discussion  
### The Influence of Temperature on MoS\({}_{2}\) Growth  
The growth temperature plays a crucial role in influencing the volatility and reactions of precursors, as well as the nucleation and growth processes of MoS\({}_{2}\) films. Figure 2a-c presents optical microscopy images of MoS\({}_{2}\) films grown at 1033 K, 1053 K, and 1073 K under a fixed pressure of 70 Torr. At 1033 K, irregular and fluffy structures are observed on the substrate surface, with no well-defined grains. As the growth temperature increases to 1053 K, triangular-shaped MoS\({}_{2}\) grains appear on the surface, and with further temperature elevation, the grain size gradually increases. Thicker crystal nuclei can be observed at the center of some grains, indicating island-like growth of the MoS\({}_{2}\) films. The XPS data for the sample grown at 1053 K and 70 Torr are shown in Figure S3. The Mo 3d\({}_{3/2}\) and Mo 3d\({}_{5/2}\) peaks appear at 233.0 eV and 229.9 eV, suggesting the 4+ oxidation state of Mo. An additional peak at 227.1 eV corresponds to the S 2s state. Figure S3b shows that S 2p\({}_{3/2}\) and S 2p\({}_{1/2}\) peaks appear at 163.9 eV and 162.7 eV, indicating the 2-oxidation state of sulfur. This provides confirmation of the formation of MoS\({}_{2}\). The interlayer interactions in MoS\({}_{2}\) films are influenced by the film thickness, resulting in a thickness-dependent characteristic of the vibrational mode frequencies. Figure 2d presents the Raman spectra of MoS\({}_{2}\) films grown at different temperatures. The Raman frequency difference between the \(E_{2g}\)1 and \(A_{1g}\) modes for the MoS\({}_{2}\) films grown at 1053 K and 1073 K are 21.1 cm\({}^{-1}\) and 21.4 cm\({}^{-1}\), respectively, which corresponds to the bilayer MoS\({}_{2}\) films, indicating the presence of small crystallites on top of the monolayer MoS\({}_{2}\). For the MoS\({}_{2}\) film grown at 1033 K, the frequency difference is 26.3 cm\({}^{-1}\), suggesting that the film thickness has exceeded four layers [33]. Figure 2e presents the PL spectra of MoS\({}_{2}\) films grown at different temperatures. It includes a strong A-excitonic peak around 681 nm and a weak B-excitonic peak around 632 nm. The A-excitonic peak is highly sensitive to the film's quality and thickness [34]. As the film thickness increases, the intensity of the A-excitonic peak undergoes quenching. The following section focuses on analyzing the impact of temperature on the reaction process. First, temperature affects the evaporation rates of S\({}_{2}\) and Mo\({}_{3}\)O\({}_{9}\). In this study, the evaporation rates of S\({}_{2}\) and Mo\({}_{3}\)O\({}_{9}\) were obtained by measuring the consumption of sulfur (S) and MoO\({}_{3}\). At a pressure of 70 Torr and a temperature of 423 K, the evaporation rate of S\({}_{2}\) was 1.26 \(\times\) 10\({}^{-3}\) mol min\({}^{-1}\) cm\({}^{-2}\). Additionally, the evaporation rate of MoO\({}_{3}\) was tested at different temperatures under a pressure of 70 Torr, as shown in Table 1.  
As the temperature increased, the evaporation rate of Mo\({}_{3}\)O\({}_{9}\) rapidly increased from 1.9 \(\times\) 10\({}^{-4}\) mol min\({}^{-1}\) cm\({}^{-2}\) at 1033 K to 6.6 \(\times\) 10\({}^{-4}\) mol min\({}^{-1}\) cm\({}^{-2}\) at 1073 K.  
Based on the experimental conditions, the finite element model was set up with the temperatures of the IV region at 1033 K, 1053 K, and 1073 K for calculation. Figure S4 shows the temperature distribution in the CVD system along with the cross-sectional temperature distribution at the center of the substrate. At a set temperature of 1033 K, the substrate temperature is only 884 K. This is because the gas flow carries away additional heat as it passes over the substrate. As the set temperature increases, the substrate temperature also rises, but the temperature difference between the set temperature and the substrate temperature gradually becomes larger.