Thin Films Processed by SILAR Method

*Md Abdul Majed Patwary*

### **Abstract**

SILAR is one of the simplest techniques in terms of the better flexibility of the substrate choice, capability of large-area fabrication, deposition of stable and adherent film, low processing temperature for the film fabrication as well as reproducibility. This technique is very budget friendly since it does not require any sophisticated equipment. Moreover, various fabrication parameters such as solution concentration, precursors, the number of cycles during immersion, pH, annealing, doping, and growth temperature affect the rate of fabrication as well as the structural, optical, and electrical properties of the fabricated thin films led the technique unique to study in an extensive manner. A chapter regarding different aspects of semiconductors-based optoelectronics by SILAR has yet to be published. This chapter will concern the recent progress that has recently been made in different aspects of materials processed by the SILAR. It will describe the theory, mechanism, and factors affecting SILAR deposition as well as recent advancements in the field. Finally, conclusions and perspectives concerning the use of materials in optoelectronic devices will be represented.

**Keywords:** SILAR, thin films, supercapacitors, photovoltaics, water splitting

### **1. Introduction**

The successive ionic layer adsorption and reaction (SILAR) technique was first introduced in 1985 by Nicolau for the deposition of ZnS and CdS [1], and Ristov et al. for the deposition of Cu2O thin films [2]. Nicolau applied the adsorption technique of film preparation, relating two sources—a metal source of aqueous solutions of CdSO4 or ZnSO4, and a sulfide source of Na2S, maintaining ambient temperature. The substrate was dipped in each of the solutions following consecutive cycles, applying rinsing steps in between to eliminate excessive precursors. In the case of Ristov et al., the method was employed using clean glass substrates, which were sequentially immersed into a solution of NaOH and a Cu-complex such as [Cu(S2O3)] to prepare Cu2O thin films. The complex [Cu(S2O3)] was well-maintained at ambient temperature, while the NaOH solution was kept at a temperature range from 60 to 80°C. The outstanding structural, electronic, and optical properties of the thin films produced in the two investigations stimulated the persistence of the practices. Hence, the technique was functional to the fabrication of a large variety of thin film semiconductors till to date [3–5]. Consequently, SILAR appeals huge scientific attention and has been well known as a facile technique for the fabrication of thin films of metal oxides,

sulfides, selenides, peroxides, and hydroxides, as well as more complex heterostructured thin films [6–11]. Compared with the other popular deposition techniques, SILAR is unique due to multiple reasons [3, 12–14] as mentioned below:


Therefore, SILAR is a vastly multipurpose and influential process for the fabrication of numerous thin film materials having huge technological attention and, hence, unlocked a wide window in optoelectronic device applications.
