Aerosol‐Assisted Chemical Vapor Deposition of NbS₂ and TaS₂ Thin Films from Pentakis(dimethylamido)metal Complexes and 2‐Methylpropanethiol

Abstract

Thin films of NbS 2 and TaS 2 have been produced from [M(NMe 2 ) 5 ] (M = Nb, Ta) and tBuSH by aerosol-assisted chemical vapor deposition on glass. Gold-colored, reflective films were obtained and deposition took place at 250-350°C for NbS 2 and 225-450°C for TaS 2 using dichloromethane or hexanes as solvent. The niobium and tantalum sulfide films were analyzed by Raman spectroscopy, scanning electron microscopy (SEM), X-ray powder diffraction, energy dispersive analysis of X-rays (EDAX) and X-ray photoelectronThe layered transition-metal dichalcogenides, which include tantalum disulfide and niobium disulfide, exhibit a number of interesting properties as a result of their structure. Thus, the layered structure has resulted in transitionmetal dichalcogenides having diverse applications, such as high-temperature lubricants, catalysts and also in photovoltaic cells. [1][2][3] Tantalum disulfide in particular has been tested for use in lithium ion batteries, while NbS 2 has been shown to be an effective humidity sensor, in addition to uses as a catalyst in hydrotreating petroleum cuts.[4-9] These applications require a high surface area for optimum performance suggesting that thin film formation would be favorable. However, there are only limited reports of thin film formation of either NbS 2 or TaS 2 . [3,[10][11][12][13][14][15] Physical deposition of NbS 2 films has been achieved by dipping the substrate into a NbS 2 powder layer, lying at the interface between water and an organic solvent. [5,10] This produced films with the basal planes parallel to the substrate's surface. Chemical vapor deposition (CVD) from single-source precursors of the form [NbCl 4 (S 2 R 2 ) 2 ][NbCl 6 ] [R = CH 3 or CH(CH 3 ) 2 ] produced mixed NbS 2 /Nb 2 O 5 films.[11] However, the films formed were very thin (Յ1000 Å) due to insufficient volatility of the precursors. Niobium monosulfide (NbS) films were deposited by lowpressure CVD from the homoleptic niobium thiolate [Nb(SC 6 H 3 Me 2 -2,6) 5 ].[12] We have recently reported the formation of NbS 2 films by atmospheric pressure CVD from the reaction of NbCl 5 with a range of sulfur precursors. [13] It was found that reaction of [14,15] To the best of our knowledge, this paper represents the first thin film growth of TaS 2 by CVD and a novel aerosolassisted (AA)CVD route to MS 2 (M = Nb, Ta) from [M(NMe 2 ) 5 ] and tBuSH. Different and unique morphologies of films can be obtained by AACVD due to the influence of the solvent on the deposition, which could potentially lead to improved properties. Furthermore, thin films can be deposited under AACVD conditions at low temperatures and require only minimal amounts of precursor (ca. 0.1 g). In this study, niobium and tantalum thiolates were generated in situ from the reaction of [M(NMe 2 ) 5 ] and tBuSH in hexanes or dichloromethane. An aerosol of this reaction mixture was then passed over a heated glass substrate, which resulted in the deposition of thin films of niobium and tantalum sulfide. The synthesis and crystal structure of the tant...

Processing and Applications of Aerosol‐Assisted Chemical Vapor Deposition

“…[105] In some cases, H 2 S gas is used to avoid the oxidation and enhance the sulfidizing reaction. [89,103] Using AACVD, highly oriented crystalline films can be synthesized, [13,90,94] even on amorphous substrates. [98] Varying and unique surface morphology of the films can be obtained by changing the solvent of the precursor.…”

Combining single source chemical vapour deposition precursors to explore the phase space of titanium oxynitride thin films

“…Chemical vapour deposition (CVD) is a widely used and scalable technique for thin film growth, [4][5][6][7] and can be used to deposit films of oxides, sulfides, nitrides and indeed mixed anion materials. 4,[8][9][10] However, compared to simple binary phases, mixed anion materials present a significantly greater challenge as their ternary phase diagrams can contain multiple stable structural phases with different anion ratios. It is essential that the deposition route can allow for selective formation of a specific, desired composition.…”

Tantalum disulfide quantum dots: preparation, structure, and properties

“…2e and was deconvoluted into components, such as Ta 4f 7/2 (23.2 eV), Ta 4f 5/2 (25.6 eV), and Ta 4f 7/2 (27.2 eV). The Ta 4f 7/2 peak at 27.2 eV is associated with oxidized tantalum [24,25]; oxidation has also been observed in other QDs [26][27][28]. and A 1g modes relate to the in-plane and out-of-plane vibration respectively [29].…”