## 3 Discussion  
The photo-dissociation of free-standing CS2 liquid samples were performed as a function of time and different sample volumes. The immediate photo-dissociation and a deposit formation were observed within one minute of VUV irradiation. After 3 min, most liquid phase samples disappear due to photo-dissociation or vaporization of the original compound. Figure 3 shows the SEM images of microdeposits formed on the Si substrate after 3 min of VUV irradiation in various CS2 sample volumes. The deposited area in each sample is proportional to the quantitative volumes of CS2. The darker area is a deposited area from the CS2 precursor decomposition, and lighter areas indicate the Si substrate. When the CS2 precursor is applied to the Si substrate, it immediately evaporates without leaving any residues. However, the 172 nm photons convert the free standing precursors into different morphology films in either N2 or air environment, covering the entire Si substrate. The VUV photons also make a selective reaction pathway to a specific product by the modification of reaction parameters during the process. The initial process condition of an N2 environment was chosen to form an inert condition because N2 does not react with VUV. It also helps VUV photons travel to the target substrate without any absorption from environmental contaminants. On the other hand, the ambient O2 gas efficiently absorbs the VUV photons to form an oxygen atom species (O) or ozone (O3). These new species can modify the existing reaction mechanism of the CS2 dissociation process and create alternative synthetic pathways. The experiments under the air environment were made to compare the photochemistry of N2. Samples from air environment yielded a different morphology than was obtained from the N2 environment. The formation rate in air was close to the rate in the N2 environment. Figure 4 shows the results of EDX analysis for deposit samples on the Si substrate, and the table provides the information of a possible composition of identified components in the deposited layer. For the test samples obtained in the N2 environment (Figure 4a), the atomic percentages of carbon (C) and sulfur (S) exhibit 15.7% and 0.35%, respectively. Only a negligible content of S element was observed in the layer. It strongly indicates that high energy photons of the microplasma  
Figure 3: SEM images of microdeposits formed on a Si substrate during the irradiation of 172 nm VUV photons for 3 min. The different amounts of precursors are irradiated: (**a**) 0.2 mL, (**b**) 0.5 mL, (**c**) 1 mL, (**d**) 3 mL of CS2 under nitrogen environment at 300 K.  
lamp effectively dissociates the C=S bond of CS\({}_{2}\) and creates a deposit with carbon-rich composites (with a possible base-bonding unit of C-C and/or C-S-C). By switching the gas environment from N\({}_{2}\) to air in Figure 4b, the atomic percentages of C, S, and O were 20.37%, 1.49%, and 1.5%, respectively. As is discussed previously, strong co-absorption of O\({}_{2}\) for VUV photons results in the participation of oxygen species in the chemical reactions. The most probable product from this oxidative process is the formation of O-C-S-based compounds, and it is a standard component identified in other oxidation processes of CS\({}_{2}\)[14; 15]. It should be also noted that the atomic percentage ratio of each elements is considered as a relative proportional values because of the involvement of Si wafer (substrate) as a primary elementsl in the EDS analysis. Figure 5 shows the Raman spectroscopy for the deposit compounds as well as the spectrum from the Si substrate as a reference. CS\({}_{2}\) is a strong Raman scatter due to its symmetric chemical structure and vibration modes. The comparison of vibrational modes in the Raman spectra between the CS\({}_{2}\) driven products is straightforward [16; 17]. In the spectra of two deposit samples, any vibrations of CS\({}_{2}\) molecule (typically at 656 and 800 cm\({}^{-1}\)) were identified, indicating that the CS\({}_{2}\) was fully decomposed by VUV irradiation.