Growth of crystalline AgIn5S8 thin films on glass substrates from aqueous solutions

Thin films of the silver indium sulfide (AgIn5S8) ternary semiconductor were prepared from acidic aqueous solutions containing silver nitrate, indium nitrate, and thioacetamide. Various preparative parameters, such as pH of the precursor solution, silver to indium concentration ratio [Ag]/[ln], and postreaction thermal treatment conditions were changed in order to grow uniform and adherent thin films on glass substrates. A series of X-ray diffraction patterns and scanning electron micrographs were used to reveal the growth process over time. It was found that granular Ag2S primary films were first attached to the glass substrate, followed by the indium sulfide deposition. A (111) preferred oriented AgIn5S8 with cubic spinel structure was obtained from the [Ag]/[In] = 4 and pH 0.6 precursor solution after 673 K thermal treatment for I h in an Ar environment. A two-step deposition mechanism was proposed and discussed in terms of stability constants of metal complexes and classical nucleation theory. In addition, our preliminary study showed that 3-mereaptopropyl-trimethoxysilane (MPS)-modified glass substrates further promoted the homogeneity and adhesion of AgIn5S8 thin films.