# Recent Advances in the Growth and Characterizations of SILAR-Deposited Thin Films
## 2 Metal Sulfide Thin Films
### Zinc Sulfide Films  
Zinc acetate or acetic acid, zinc(II) salt (Zn(CH\({}_{3}\)CO\({}_{2}\))\({}_{2}\)), and sodium sulfide solution were used to produce ZnS films onto the glass substrate [38]; the growth mechanisms are explained in Equations (6)-(9). \[\mathrm{Zn(CH_{3}COO)}_{2}\rightarrow\mathrm{Zn^{2+}+2 CH_{3}COO^{-}} \tag{6}\]  
\[\mathrm{Na_{2}S+H_{2}O\rightarrowNa^{+}+SH^{-}} \tag{7}\]  
\[\mathrm{OH^{-}+SH^{-}\rightarrowH_{2}O+S^{2-}} \tag{8}\]  
\[\mathrm{Zn^{2+}+S^{2-}\rightarrowZnS} \tag{9}\]  
The formations of ZnS films were reported by using zinc acetate, thiourea, and a complexing agent (ammonium hydroxide, (NH\({}_{4}\)OH)). Based on the photoluminescence studies, three sharp peaks (413, 480, and 525 nm) could be detected. Further, the reduction  
Figure 2: Schematic of the synthesis of CTS thin films by the SILAR method reproduced with permission from [33], [PERSON], 2017.  
of the intensity due to the concentration of sulfur increased [39]. The deposition of thin films onto fluorine-doped tin oxide glass was reported by [PERSON] and co-workers [40]. The band gap reduced from 3.62 to 3.5 eV when increasing the deposition cycle (40 to 70 cycles). The FESEM analysis revealed a mesoporous nature and a thickness of 1.43 \(\upmu\)m. Photovoltaic parameters were studied by using the photoelectrochemical solar cell. The fill factor, power conversion efficiency, open circuit voltage (V\({}_{\text{oc}}\)), and short circuit current (J\({}_{\text{sc}}\)) were 0.59, 0.1%, 0.52 V, and 0.35 mA/cm\({}^{2}\), respectively, when the films were prepared under 70 deposition cycles. Zinc (II) chloride (ZnCl\({}_{2}\)), triethanolamine, and sodium sulfide solutions were used to produce films [41]. The XRD studies confirmed that the amorphous phase changed to the crystalline phase as the deposition temperature increased. Ammonia was used as a complexing agent during the preparation of films [42]. The obtained films showed a crystallite size of about 12 nm with a thickness of 1 \(\upmu\)m. The activation energy was 0.6 eV, and an increase in temperature caused a decrease in electrical resistance. [PERSON] and co-workers [43] reported that the growth rate of films deposited on a gallium arsenide (GaAs) substrate was 0.23 nm per cycle. The XRD studies revealed that the highest reflection could be seen at 29\({}^{\circ}\), contributing to the (111) plane in the films (film thickness = 136 nm). Experimental findings showed the highest tensile stress (6.9 \(\times\) 10\({}^{8}\) N/m\({}^{2}\)) for the obtained films (surface roughness = 2.9 nm, thickness = 50 nm). The soda-lime glass was used to produce films [44] by using TEA under the immersion time (20 s). The refractive indices and growth rates were 1.95-2.23 and 0.13-0.27 nm/cycle, respectively. To our knowledge, there was only one publication published on zinc sulfide thin films, produced by using two deposition techniques (the SILAR method and thermal evaporation technique). This comparison was very unique (Table 2); the properties of the obtained thin films were studied for the first time.