Characterization of Zn1-xLaxS thin films; compositional, surface, optical, and photoluminescence properties for possible optoelectronic and photocatalytic applications

The influences of La3+ substituent levels (x = 0-15 at. %) on the structural, surface, optical, photoluminescence, and optical constants of the Zn1-xLaxS (ZLS) thin films, synthesized by sol-gel dip-coating technique were investigated. The derived films have a predominant cubic structure with principally favored crystal plane direction of (111) and hexagonal phase. The crystalline quality and directional orientation of the ZLS thin films varied with the La(3+)substitution level. The surface anatomy of the films was dense and homogeneous and the average facet roughness was enhanced by increasing the La(3+)substitution level. UV-Vis explorations clarified that the La(3+)substitution resulted in a decrement in the band gap energy of the ZLS samples except for certain La(3+)substitution levels. The photoluminescence spectra exhibited that all samples emitted four chief emissions due to the near band and their variant crystal defects. The obtained optical constants showed strong dependence on the La(3+)substitution level and the highest values of them were detected for the 10 % La3+ substitution level. Among the produced film samples, the ZnS film sample with 10% La3+ substitution exhibited the best film crystallization and optical quality. Thus, it shows promise as a relatively suitable material for optoelectronic, solar cell, and photocatalytic applications, given its tunable characteristics.