Template-Free Vapor-Phase Growth of Patrónite by Atomic Layer Deposition
2017-03-09T00:00:00Z (GMT) by
Despite challenges to control stoichiometry in the vanadium–sulfur system, template-free growth of patrónite, VS<sub>4</sub>, 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 VS<sub>4</sub> is established via <i>in situ</i> 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 H<sub>2</sub>S half-cycle generates the disulfide dimer moiety, S<sub>2</sub><sup>–2</sup>, and oxidizes V<sup>3+</sup> to V<sup>4+</sup>. X-ray analysis establishes VS<sub>4</sub> 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/cm<sup>3</sup>. Phase pure films enable a new assignment of vibrational modes and corresponding Raman activity of VS<sub>4</sub> 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, V<sub>2</sub>S<sub>3</sub>.
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