Zinc sulfide (ZnS) is one of the first semiconductors discovered. It has traditionally shown remarkable versatility and promise for novel fundamental properties and diverse applications. The nanoscale morphologies of ZnS have been proven to be one of the richest among all inorganic semiconductors. In this article, we provide a comprehensive review of the state-of-the-art research activities related to ZnS nanostructures. We begin with a historical background of ZnS, description of its structure, chemical and electronic properties, and its unique advantages in specific potential applications. This is followed by in-detail discussions on the recent progress in the synthesis, analysis of novel properties and potential applications, with the focus on the critical experiments determining the electrical, chemical and physical parameters of the nanostructures, and the interplay between synthetic conditions and nanoscale morphologies. Finally, we highlight the recent achievements regarding the improvement of ZnS novel properties and finding prospective applications, such as field emitters, field effect transistors (FETs), p-type conductors, catalyzators, UV-light sensors, chemical sensors (including gas sensors), biosensors, and nanogenerators. Overall this review presents a systematic investigation of the ‘synthesis-property-application’ triangle for the diverse ZnS nanostructures.

ZnS nanostructures: From synthesis to applications

We present a simple, easily scalable route to monodisperse copper sulfide nanocrystals by the hot injection of a series of novel copper(I) xanthate single-source precursors [(PPh3)2Cu(S2COR)] (R = isobutyl, 2-methoxyethyl, 2-ethoxyethyl, 1-methoxy-2-propyl, 3-methoxy-1-butyl, and 3-methoxy-3-methyl-1-butyl), whose crystal structures are also reported. We show that the width of the obtained rods is dependent on the length of the xanthate chain, which we rationalize through a computational study, where we show that there is a relationship between the ground-state energy of the precursor and the copper sulfide rod width.

Novel Xanthate Complexes for the Size-Controlled Synthesis of Copper Sulfide Nanorods.

A family of tin(II) guanidinate complexes of the general form [{RNC(NMe2)NR}2Sn] (R = iPr (6), Cy (7), Tol (9) and Dipp (10)) and [{tBuNC(NMe2)NtBu}Sn{NMe2}] (8) have been synthesised and isolated from the reaction of tin(II) bis-dimethylamide and a series of carbodiimides (1–5). The cyclic poly-chalcogenide compounds [{CyNC(NMe2)NCy}2Sn{Chx}] (Ch = S, x = 4 (11); Ch = Se, x = 4 (12), and Ch = S, x = 6 (13)) with {SnChx} rings were prepared by the oxidative addition of elemental sulfur and selenium to the heteroleptic stannylene complex [{CyNC(NMe2)NCy}2Sn] (7) in THF at room temperature. Similarly, reaction of compounds 6 and 7 with an equimolar amount of the chalcogen transfer reagents (SC3H6 and SePEt3, respectively) led to the formation of the chalcogenide tin(IV) complexes [{RNC(NMe2)NR}Sn(Ch)] (R = Cy: Ch = S (14); R = iPr, Ch = Se (15); R = Cy, Ch = Se (16)) with terminal SnCh (14 and 16) and dimeric bridged seleno-tin {Sn2Se2} rings (15), respectively. The mono telluro-compounds [{RNC(NMe2)NR}Sn(Te)] (R = iPr (17); R = Cy (18)) were similarly prepared by the oxidative addition of elemental tellurium to 7 and 8, respectively. All of the tin containing compounds have been investigated by multinuclear NMR (1H, 13C 119Sn and 77Se/125Te, where possible), elemental analysis and single crystal X-ray structural analysis (7, 8, 10–13, 15–18). Thermogravimetric analysis (TGA) was used to probe the possible utility of complexes 6–8, 11–12 and 14–18 as single source Sn and SnCh precursors. The Sn(II) compounds 6 and 7 have been utilised in the growth of thin films by aerosol-assisted chemical vapor deposition (AACVD) at both 300 and 400 °C. The thin films have been analysed by pXRD, EDS, SEM and AFM and shown to be Sn metal. Subsequent studies provided film growth at temperatures as low as 200 °C. Similarly, the mono-chalcogenide systems 14, 16 and 18 have been utilised in the AACVD of thin films. These latter studies provided films, grown at 300 and 400 °C, which have also been analysed by pXRD, Raman spectroscopy, AFM, and SEM and are shown to comprise phase pure SnS, SnSe and SnTe, respectively. These preliminary results demonstrate the potential of such simple guanidinate complexes to act as single source precursors with a high degree of oxidative control over the deposited thin films.

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Tin guanidinato complexes: oxidative control of Sn, SnS, SnSe and SnTe thin film deposition

Indium nitride (InN) is characterized by its high electron mobility making it a ground-breaking material for high frequency electronics. The difficulty of depositing high-quality crystalline InN cu...

In Situ Activation of an Indium(III) Triazenide Precursor for Epitaxial Growth of Indium Nitride by Atomic Layer Deposition

We report the synthesis and single-crystal X-ray characterization of diphenyltin bis(2-methoxyethylxanthate) and diphenyltin bis(iso-butylxanthate). These xanthates have been used as a single-source precursor to deposit tin chalcogenide thin films by aerosol-assisted chemical vapor deposition. Grazing incidence X-ray diffraction and scanning transmission electron microscope imaging coupled with elemental mapping show that films deposited from diphenyltin bis(iso-butylxanthate) contain orthorhombic SnS, while films deposited from diphenyltin bis(2-methoxyethylxanthate) between 400 and 575 °C form a SnS/SnO2 nanocomposite. In synthesizing the thin films, we have also demonstrated an ability to control the band gap of the materials based on composition and deposition temperature.

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Chemical vapor deposition of tin sulfide from diorganotin(IV) dixanthates

Bis-3-methylpyridine and bis-4-methylpyridine complexes of cadmium(II) ethylxanthate have been characterized by elemental analysis, NMR spectroscopy, and thermogravimetric analysis. The single crystal X-ray structures of both methylpyridine derivatives have also been determined and shown to display a cis, cis, cis-configuration of the N- and S-donor ligands. The compounds have been utilized as single source precursors to deposit CdS films on silica-coated glass substrates at 220 and 350 °C by aerosol-assisted chemical vapor deposition. The surface morphology of the films has been examined by scanning electron microscopy analysis and the crystalline phases were studied by powder X-ray diffraction. The films deposited from the 3-methylpyridine adduct comprised more densely packed and more highly crystalline hexagonal CdS than those provided by either of the other two precursors. The crystallite sizes were found to be <20 nm for films deposited from the pyridine and 4-methylpyridine adducts but to display a ...

Aerosol-Assisted Chemical Vapor Deposition of CdS from Xanthate Single Source Precursors

The stannous alkoxides [Sn(OR)2] [R = i-Pr, t-Bu, C(Et)Me2, CHPh2, CPh3] have been synthesised by reaction of Sn(NR′2)2 with two equivalents of HOR [R′ = Me, R = i-Pr; R′ = SiMe3, R = t-Bu, C(Et)Me2, CHPh2, CPh3]. Single crystal X-ray diffraction analysis of the bis(diphenylmethoxide) (4) and bis(triphenylmethoxide) (5) species have shown them to comprise three-coordinate Sn(II) centres through dimerisation in the solid state with the alkoxide units adopting transoid and cisoid configurations across the {Sn2O2} cores respectively. Thermogravimetric analysis indicates clean decomposition and some evidence of volatility at temperatures >200 °C for all three aliphatic alkoxides, whereas both the diphenyl- and triphenylmethoxide compounds provide higher decomposition temperatures and, for the triphenylmethoxide derivative, a residual mass consistent with the formation of a carbon-containing residue. The previously reported iso-propoxide (1) and tert-butoxide (2) derivatives have been utilised in toluene solution to deposit SnO thin films by aerosol-assisted chemical vapour deposition (AACVD) on glass at temperatures between 300 and 450 °C. While SnO is deposited under hot wall conditions as the only identifiable phase by p-XRD and Raman spectroscopy for both precursors, morphological analysis by SEM reveals inferior substrate coverage in comparison to previously reported ureide-based precursor systems.

Aerosol-assisted CVD of SnO from stannous alkoxide precursors

One field of organometallic and materials chemistry that has seen great advancements over the last 20 years is that of atomic layer deposition (ALD), and in particular the development of precursors for the deposition of thin films of highly functional materials. This review focuses on newly developed ALD precursors for metals and metalloid elements (Groups I to XV). New precursors are necessary for a wide range of both established and emerging high-tech applications. A brief overview of recent advances in precursor chemistry is given.

Recent developments in molecular precursors for atomic layer deposition

A family of 12 zinc(II) thoureide complexes, of the general form [{L}ZnMe], [{L}Zn{N(SiMe3)2}], and [{L}2Zn], have been synthesized by direct reaction of the thiourea pro-ligands iPrN(H)CS(NMe2) H[L1], CyN(H)CS(NMe2) H[L3], tBuN(H)CS(NMe2) H[L2], and MesN(H)CS(NMe2) H[L4] with either ZnMe2 (1:1) or Zn{N(SiMe3)2}2 (1:1 and 2:1) and characterized by elemental analysis, NMR spectroscopy, and thermogravimetric analysis (TGA). The molecular structures of complexes [{L1}ZnMe]2 (1), [{L2}ZnMe]2] (2), [{L3}ZnMe]∞ (3), [{L4}ZnMe]2] (4), [{L1}Zn{N(SiMe3)2}]2 (5), [{L2}Zn{N(SiMe3)2}]2 (6), [{L3}Zn{N(SiMe3)2}]2] (7), [{L4}Zn{N(SiMe3)2}]2] (8), [{L1}2Zn]2 (9), and [{L4}2Zn]2 (12) have been unambiguously determined using single crystal X-ray diffraction studies. Thermogravimetric analysis has been used to assess the viability of complexes 1–12 as single source precursors for the formation of ZnS. On the basis of TGA data compound 9 was investigated for its utility as a single source precursor to deposit ZnS films on si...

Aerosol-Assisted Chemical Vapor Deposition of ZnS from Thioureide Single Source Precursors.

SnO is a rare example of a stable p-type semiconductor material. Here, we describe the synthesis and characterisation of a family of Sn(II) pyrrolide complexes for future application in the MOCVD and ALD of tin containing thin films. Reaction of the Sn(II) amide complex, [{(Me3Si)2N}2Sn], with the N,N-bidentate pyrrole pro-ligand, L1H, forms the hetero- and homoleptic complexes [{L1}Sn{N(SiMe3)2}] (1) and [{L1}2Sn] (2), respectively, bearing the 2-dimethylaminomethyl-pyrrolide ligand (L1). Reaction of [{(Me3Si)2N)}2Sn] with the pyrrole-aldimine pro-ligands, L2H–L7H, results in the exclusive formation of the homoleptic bis-pyrrolide complexes [{L2–7}2Sn] (3–8). All complexes have been characterised by elemental analysis and NMR spectroscopy, and the molecular structures of complexes 1–5 and 8 are determined by single crystal X-ray diffraction. TG analysis and isothermal TG analysis have been used to evaluate the potential utility of these systems as MOCVD and ALD precursors.

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James D. Parish

Papers

Aerosol-Assisted Chemical Vapor Deposition of CdS from Xanthate Single Source Precursors

Aerosol-assisted CVD of SnO from stannous alkoxide precursors

Recent developments in molecular precursors for atomic layer deposition

Aerosol-Assisted Chemical Vapor Deposition of ZnS from Thioureide Single Source Precursors.

Synthesis, characterisation and thermal properties of Sn(ii) pyrrolide complexes.