Surface-engineered growth of AgIn₅S₈ crystals

The growth of semiconductor crystals and thin films plays an essential role in industry and academic research. Considering the environmental damage caused by energy consumption during their fabrication, a simpler and cheaper method is desired. In fact, preparing semiconductor materials at lower temperatures using solution chemistry has potential in this research field. We found that solution chemistry, the physical and chemical properties of the substrate surface, and the phase diagram of the multicomponent compound semiconductor have a decisive influence on the crystal structure of the material. In this study, we used self-assembled monolayers (SAMs) to modify the silicon/glass substrate surface and effectively control the density of the functional groups and surface energy of the substrates. We first employed various solutions to grow octadecyltrichlorosilane (OTS), 3-mercaptopropyl-trimethoxysilane (MPS), and mixed OTS-MPS SAMs. The surface energy can be adjusted between 24.9 and 50.8 erg/cm². Using metal sulfide precursors in appropriate concentrations, AgIn₅S₈ crystals can be grown on the modified substrates without any post-thermal treatment. We can easily adjust the nucleation in order to vary the density of AgIn₅S₈ crystals. Our current process can achieve AgIn₅S₈ crystals of a maximum of 1 μm in diameter and a minimum crystal density of approximately 0.038/μm². One proof-of-concept experiment demonstrated that the material prepared from this low temperature process showed positive photocatalytic activity. This method for growing crystals can be applied to the green fabrication of optoelectronic materials.