Template-Free Vapor-Phase Growth of Patrónite by Atomic Layer Deposition

Despite challenges to control stoichiometry in the vanadium-sulfur system, template-free growth of patrónite, VS₄, thin films is demonstrated for the first time. A novel atomic layer deposition (ALD) process enables the growth of phase pure films and the study of electrical and vibrational properties of the quasi-one-dimensional (1D) transition metal sulfide. Self-limiting surface chemistry during ALD of VS₄ is established via in situ quartz crystal microbalance and quadrupole mass spectrometry between 150 and 200 °C. The V precursor, unconventionally, sheds all organic components in the first half-cycle, while the H₂S half-cycle generates the disulfide dimer moiety, S₂^-2, and oxidizes V³⁺ to V⁴⁺. X-ray analysis establishes VS₄ crystallinity and phase purity, as well as a self-limiting growth rate of 0.33 Å/cy, modest roughness of 2.4 nm, and expected density of 2.7 g/cm³. Phase pure films enable a new assignment of vibrational modes and corresponding Raman activity of VS₄ that is corroborated by density functional theory (DFT) calculations. Finally, at elevated growth temperatures, a change in the surface mechanism provides a synthetic route to a second vanadium-sulfur phase, V₂S₃.