## 3 Results and Discussion  
### Development of a Process Proper for Obtaining a Thick SnS Film Using ALD  
We first performed a vacuum annealing process of ALD-deposited a-SnS\({}_{2}\) film to fabricate the thick SnS film. The XRD patterns, shown in Figure 1b,c, exhibited the dependence of temperature and time conditions on the vacuum annealing process, respectively. As shown in Figure 1b, when the a-SnS\({}_{2}\) films were annealed at various temperatures for 10 min, crystalline SnS phases were observed at 400 and 450 \({}^{\circ}\)C. The XRD peaks of samples annealed at 400 and 450 \({}^{\circ}\)C indicated orthorhombic SnS corresponding to diffraction data reference of JCPDS standard card #23-0677. In particular, the XRD pattern of the film annealed at 400 \({}^{\circ}\)C for 10 min was almost the same as that of the JCPDS reference, and the peaks became sharp. At the annealing temperature of 350 \({}^{\circ}\)C, the phase transition from SnS\({}_{2}\) to SnS was also observed. However, the a-SnS\({}_{2}\) film was not completely transformed into crystalline SnS. The main (001) peak of hexagonal SnS\({}_{2}\) phase was observed at 15.03\({}^{\circ}\). Further, there were additional low intensity peaks positioned at 16.10\({}^{\circ}\), 21.48\({}^{\circ}\), 28.80\({}^{\circ}\), 33.78\({}^{\circ}\), 40.12\({}^{\circ}\), and 50.08\({}^{\circ}\). These are peaks of orthorhombic SnS\({}_{2}\)S\({}_{3}\) crystal phase found in JCPDS #75-2183. Because Sn\({}_{2}\)S\({}_{3}\) generally appears as a mixed phase in tin sulfide films, it is interpreted that Sn\({}_{2}\)S\({}_{3}\) crystals appeared as a metastable phase in the intermediate step of the transformation of SnS\({}_{2}\) to SnS. Alternatively, the Sn\({}_{2}\)S\({}_{3}\) as a phase impurity contained in a-SnS\({}_{2}\) film may have been crystallized. As the annealing temperature was increased above 400 \({}^{\circ}\)C, the sharpness of SnS peaks decreased, and no peaks were observed at 500 \({}^{\circ}\)C. In an actual experiment, it was identified that the a-SnS\({}_{2}\) film completely volatilized on the substrate at the annealing temperature of 500 \({}^{\circ}\)C. Therefore, 400 \({}^{\circ}\)C was the optimal annealing temperature, as shown in Figure 1b. Figure 1c shows the XRD results of a-SnS\({}_{2}\) films annealed with various time conditions at 400 \({}^{\circ}\)C. As shown in Figure 1b, when the annealing time was 10 min, almost the same SnS crystal phase as the JCPDS reference was observed. The a-SnS\({}_{2}\) film annealed for 5 and 20 min showed SnS peaks with lower sharpness than the sample annealed for 10 min. The main (001) peak of hexagonal SnS\({}_{2}\) and the peaks of Sn\({}_{2}\)S\({}_{3}\) were also detected in the 5 min annealed sample. Further, the sample annealed for 30 min was completely volatilized on the substrate. Thus, Figure 1b,c show that the a-SnS\({}_{2}\) film completely transformed into a polycrystalline SnS film under the annealing conditions of 400 \({}^{\circ}\)C for 10 min. The crystallization behavior in this experiment was different from our previous reports that directly deposited SnS film by ALD, which showed only a main (111) peak of orthorhombic SnS phase at 31.53\({}^{\circ}\)[25]. Furthermore, this process used a high growth rate of 5.3 A/cycle. Compared to the previous study, the growth rate of this a-SnS\({}_{2}\) process was very high. In an earlier study on atomic layer deposition of tin sulfide films using TDMASn and H\({}_{2}\)S by [PERSON] et al., tin sulfide film deposited at 100 \({}^{\circ}\)C had growth rate of 1.26 A/cycle [31]. At our ALD process used in this study, higher process pressure of 1.0 Torr and multidosing recipe were used, as described in the methods section. As the amorphous phase was deposited at a low temperature of 100 \({}^{\circ}\)C, the differences of pressure and recipe would increase the growth rate compared to the previous study.