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

Abstract

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.

Multi‐Electron Reactions Enabled by Anion‐Based Redox Chemistry for High‐Energy Multivalent Rechargeable Batteries

“…Besides its high theoretical capacity, the flexible quasi one-dimensional (1D) molecular structure of patronite VS 4 and the chemical softness of the sulfides can be particularly favourable for the diffusion of multivalent ions. [21] In addition, VS 4 possesses a semi-conductive nature with a small band gap of only around 1.0 eV, [9b] which is beneficial for electron transfer, as well. We present a comprehensive mechanistic and theoretical study that reveals that VS 4 undergoes interesting anionic redox reactions in Mg and Ca based batteries.…”

Multi‐Electron Reactions Enabled by Anion‐Based Redox Chemistry for High‐Energy Multivalent Rechargeable Batteries

“…The signal at 343 cm −1 is attributed to the V 2 S 4 ‐cage breathing. While the modes at 271 cm −1 , 285 cm −1 , and 540–550 cm −1 are indicative of S−S bond stretching and twisting from the S 2 2− group [21, 23] …”

“…Herein, we investigated VS 4 as an insertion cathode based on anion based redox reactions for both rechargeable Mg and Ca batteries (RMBs and RCBs) using these new borate electrolytes, respectively. Besides its high theoretical capacity, the flexible quasi one‐dimensional (1D) molecular structure of patronite VS 4 and the chemical softness of the sulfides can be particularly favourable for the diffusion of multivalent ions [21] . In addition, VS 4 possesses a semi‐conductive nature with a small band gap of only around 1.0 eV, [9b] which is beneficial for electron transfer, as well.…”

Synthesis of Thin‐Film Metal Pyrites by an Atomic Layer Deposition Approach

“…Over the decades, the ALD technique has been developing very fast, and hundreds of differentm aterials, such as metals, metal oxides, nitrides and sulfides, have been synthesized by ALD. [18] Very recently,m otivated by many novel applicationsi n low-dimensional electronics and energy technologies, the ALD synthesis of metal sulfides has aroused significant attention, [19] and many new ALD synthesis processes have been particularly developed for metal sulfides.E xamples of them etal sulfides whose ALD synthesis approaches were only recently available include GaS x (2014), [20] GeS (2014), [21] MoS 2 (2014), [19b, 22] Li 2 S (2014), [23] Co 9 S 8 (2015), [24] NiS (2016), [25] MnS (2016), [26] FeS (2017), [27] VS 4 (2017), [28] and ReS 2 (2018). [29] Despite the fast development as above, the ALD synthesisoft he pyrite-structured metal disulfides remained as ignificant challenge for quite a long period, and none of the metal pyrites had ever been synthesized by ALD before our recent work.…”

“…The ALD process is performed in cyclic manner, where each ALD cycle consists of four sequential steps, that is, 1) dosing the metal precursor ML 2 into the deposition chamber with a sufficient amount of precursor exposure to the sample surface, 2) using a continuous inert‐gas flow to completely purge away the reaction by‐products and the unreacted excess ML 2 , 3) dosing the sulfur precursor H 2 S into the deposition chamber with a sufficient amount of precursor exposure to the sample surface, and 4) again using the continuous inert‐gas flow to completely purge away the reaction by‐products and the unreacted excess H 2 S. Assuming that the surface reactions follow an ideal and complete ligand‐exchange (metathesis) scheme, the terminating surface groups during the ALD process should be alternating between the metal‐coordinated ligand and sulfhydryl groups, as depicted in Figure a (Steps 2 and 4). However, non‐ideal reactions such as ion‐exchange, or redox reactions, have been reported for the ALD of metal sulfides, which implies that the careful choice of the ALD precursors for the surface reactions is of high importance for the metal sulfide ALD processes. The ALD precursors are desired to be of high volatility (e.g., >≈0.1 torr) and high surface reactivity, to enable rapid and efficient film growth, and the involved surface reactions should be self‐terminating to prevent unlimiting CVD‐like film growth.…”