Atomic Layer Deposition of AgX (X = Cl, Br, I) Thin Films

Silver halides (AgX, X = Cl, Br, I) are promising materials for various applications, including optical, medical, and electronic technologies, due to their light sensitivity, high refractive index, and antiseptic properties. Silver halides are also important constituents of Pb-free photovoltaic materials such as rudorffites and double halide perovskites. This study presents atomic layer deposition (ALD) processes for the deposition of silver halide thin films using (2,2-dimethyl-6,6,7,7,8,8,8-heptafluorooctane-3,5-dionato)-silver-(I)-triethylphosphine (Ag-(fod)-(PEt₃)) as the silver precursor and different halide precursors, including TiX₄, SnX₄, GaX₃, and HX (X = Cl, Br, I). The films were deposited on Si substrate at temperatures ranging from 105 to 195 °C. Grazing incidence X-ray diffraction (GI-XRD) revealed the formation of crystalline phases of AgI, AgBr, and AgCl. The choice of the halide precursor significantly affected the film morphology and purity. Titanium tetrahalides led to the most consistent growth-per-cycle (GPC) over the studied temperature range, resulting in films with superior crystallinity and purity. In particular, TiI₄ was identified as the most effective halide precursor which led to AgI films with superior continuity and purity. Although GaX₃, SnX₄, and HX precursors showed good performance in terms of GPC, the resulting films exhibited significant sensitivity to the deposition temperature and contained impurities. This study demonstrates that ALD is a robust technique for the controlled deposition of silver halides.