# Recent Advances in the Growth and Characterizations of SILAR-Deposited Thin Films
## 1 Introduction  
Thin films have attracted much interest because they possess unique properties [1]. Several physical methods and chemical deposition techniques were used for the growth of thin films on substrates. These deposition methods include electrodeposition [2], chemical bath deposition [3], magnetron sputtering, chemical vapor deposition, spray pyrolysis, thermal evaporation [4], molecular beam epitaxy, ion beam deposition, electron beam evaporation, atomic layer epitaxy, the spin coating method [5], the pulsed laser deposition method, and the successive ionic layer adsorption and reaction (SILAR) technique. The advantages and disadvantages of these deposition techniques are highlighted as shown in Table 1. The prepared thin films could be used in lasers, cathodic ray tubes, solar cells [6], infrared windows, ultraviolet light-emitting diodes, sensors [7], supercapacitors, and biologic and optoelectronic applications [8]. The advantages of the SILAR method, including a large area deposition, could be carried out in any substrate at lower temperatures by using simple techniques and inexpensive instruments [9]; stoichiometry, thickness, morphology, and grain size could be controlled [10]; there are material and production cost savings [11]; a vacuum chamber is not required; there is excellent growth rate and non-formation of precipitate in the container. Generally, the SILAR deposition technique background could be represented by the adsorption and reaction of ions (anions and cations from solutions) and the rinsing process (deionized water) to prevent precipitation in the solution. The SILAR techniqueconsists of four steps [12], namely adsorption (the cation is adsorbed on the substrate surface), the first rinsing with water (the excess adsorbed ions are rinsed away), the reaction process (introducing the anionic ion into the system), and the second rinsing (the unreacted species and excess ions are removed). The formation of thin films on the substrate could be observed by repeating these cycles [13]. The complexing agents, rinse times, immersion times, deposition cycles, concentrations of the precursor solutions, and the nature of the precursors were shown to affect the SILAR growth phenomena. In this work, specific terms, such as \"ionic product\" and \"solubility concept\" will be discussed briefly to help the reader understand the SILAR deposition technique. When the sparingly soluble salt (EF) was reacted with water, the saturated solution consisted of the A\({}^{+}\) ion and B\({}^{-}\) ion, as indicated in the following equation:  
\[\text{EF(s)}\leftrightarrow\text{E}^{+}+\text{F}^{-}\]  
\[\text{K}=\left[\text{C}_{\text{E}}^{+}\text{-C}_{\text{F}}^{-}\right]/\text{C}_ {\text{EF}}\]  
\[\text{K}\prime=\text{C}_{\text{E}}^{+}\text{-C}_{\text{F}}^{-}\]  
\[\text{K}_{\text{s}}=\text{C}_{\text{E}}^{+}\text{-C}_{\text{F}}^{-}\]  
Here, the concentrations of E\({}^{+}\), F\({}^{-}\), and EF are represented as C\({}_{\text{E}}^{+}\), C\({}_{\text{F}}^{-}\), and C\({}_{\text{EF}}\), respectively. Generally, the concentration of pure solid was considered a constant number (K\({}^{\prime}\)). We knew that K and K\({}^{\prime}\) were so-called constant values. The product of KK\({}^{\prime}\) was identified as a constant value as well and could be labeled as K\({}_{\text{s}}\). In the SILAR deposition method, Ks and C\({}_{\text{E}}^{+}\), C\({}_{\text{F}}^{-}\) are called the solubility product and ionic product, respectively. We can observe that the ionic product is equal to the solubility product in the saturated solution, In the supersaturated solution, precipitation occurs, and ions combine to produce nuclei when the ionic product is more than the solubility product. In this work, we will describe the preparation of metal sulfide, metal oxide, metal telluride, and metal selenide thin films by using the SILAR deposition technique. The thin film growth and reaction mechanisms will be highlighted based on the literature.