## 2 Experimental Method  
The operation principle of excimer lamps relies on the radiative decomposition of excimer dimers such as Xe\({}_{2}\)* (172 nm) formed in a plasma discharge of noble gases. As illustrated in Figure 1a, Xe\({}_{2}\) is well known for emitting bright continua (150, 172 nm) along with resonance lines of Xe* (129 and 147 nm). The dominant Xe\({}_{2}\) emission at 172 nm arises from A\({}^{1}\)\(\sum_{it}^{+}\)\(\rightarrow\) X\({}^{1}\)\(\sum_{g}^{+}\) transitions of the molecule and its emission intensities' growth are attributed to the three-body collision of excited state Xe* and 2 Xe ground state atoms [6]. The formation rate of these three body reactions is increased quadratically with Xe gas pressure. The structure of the microplasma lamp used here has an array of microcavities that produces a low temperature and non-equilibrium plasmas. The electron temperature of microplasma lies in the 2-5 eV interval, which is ideal for forming the excimer (Xe\({}_{2}\)) and increasing its transition intensities. Another advantage of using excimer lamps is that the non-stable ground state of an excimer lamp is able to have no self-absorption of the emitted illumination, providing a high UV intensity. In addition, the flat form factor and diffusive glow in the lamp make a uniform treatment over the area of the lamp. Therefore, the deposition area can be easily scaled along with the flat lamp size at given intensities. Figure 1: (**a**) Basic energy and transition diagram of VUV emission of Xe\({}_{2}\) excimer lamp, (**b**) Schematic potential energy curve of the target molecule, CS\({}_{2}\) with 172 nm VUV lamp energy level (red dash line). Figure 2a demonstrates the operation of the 172 nm microplasma VUV lamp (100 \(\times\) 100 mm, Eden Park Illumination, Inc. Champaign, IL, USA). The lamp is filled with 500 Torr of 70% Xe/Ne gas mixture, and operated at 20-30 kHz of 3 kV pulses. The output intensity at the surface of the lamp was 17 mW/cm\({}^{2}\). Figure 2b shows the VUV emission spectrum from the lamp. Figure 1b is a schematic of the potential energy curves in the excited states of CS\({}_{2}\)[13]. The red dashed line corresponds to the 172 nm VUV lamp photon energy (7.2 eV) in this experiment. Photon energy from the VUV lamp sufficiently covers the energies required to dissociate the C=5 bond of the CS\({}_{2}\). The configuration of the VUV photodissociation setup were shown in Figure 2c. The distance between the VUV lamp and substrate was maintained 1 cm. VUV photons are affected by environmental conditions as it is readily absorbed by surrounded chemical species such as water vapor or oxygens. It means that VUV photons cannot travel long distances. The experiment has been performed in the N\({}_{2}\) (purged) environment, which does not absorb the 7.2 eV photons, to minimize the photon losses (and observe the contribution of VUV photons to the overall reaction). Besides, we also performed the experiments at ambient (dry air) environment preferring the formation of active oxygen species by moisture and oxygen. The latter condition led to the deposition of a series of compounds (associated with oxidation, as shown in results from EDS). The distance of 1 cm was chosen from the multiple tests to find the optimal distance, which maintains the consistency between two experimental approaches and keeping a balance between photochemistry and direct photo-radiation. A shorter distance than 1 cm was not considered in these experiments to avoid any interaction between the target substrates (or chemical vapors) and the flat lamp itself. Free-standing, liquid phase CS\({}_{2}\) droplets (99.99%, Sigma-Aldrich, St. Louis, MO, USA) were applied to the Si substrate with a micropipette for quantitative sampling from 0.2 mL to 3 mL. The chamber was purged with an atmospheric pressure of either research-grade N\({}_{2}\) or dry air with a flow rate of 5 slm.