Patterning and doping of transition metals in tungsten dichalcogenides.

Substitutional transition metal doping in two-dimensional (2D) layered dichalcogenides is of fundamental importance in manipulating their electrical, excitonic, magnetic, and catalytic properties through the variation of the d-electron population. Yet, most doping strategies are spatially global, with dopants embedded concurrently during the synthesis. Here, we report an area-selective doping scheme for W-based dichalcogenide single layers, in which pre-patterned graphene is used as a reaction mask in the high-temperature substitution of the W sublattice.

Oxidation and Degradation of WS Monolayers Grown by NaCl-Assisted Chemical Vapor Deposition: Mechanism and Prevention.

The preservation of two-dimensional WS in the environment is a concern for researchers. In addition to water vapor and oxygen, the latest research points out that degradation is directly related to light absorption. Based on the selection rules of nonlinear optics, two-photon absorption is dipole forbidden in the exciton 1s states, but second-harmonic generation (SHG) is allowed with virtual transitions.

Formation of Highly Doped Nanostripes in 2D Transition Metal Dichalcogenides via a Dislocation Climb Mechanism.

Doping of materials beyond the dopant solubility limit remains a challenge, especially when spatially nonuniform doping is required. In 2D materials with a high surface-to-volume ratio, such as transition metal dichalcogenides, various post-synthesis approaches to doping have been demonstrated, but full control over spatial distribution of dopants remains a challenge. A post-growth doping of single layers of WSe is performed by adding transition metal (TM) atoms in a two-step process, which includes annealing followed by deposition of dopants together with Se or S.

Scanning Moiré Fringe Method: A Superior Approach to Perceive Defects, Interfaces, and Distortion in 2D Materials.

Scanning moiré fringe (SMF) is a widely utilized technique for the precise measurement of the strain field in semiconductor transistors and heterointerfaces. With the growing challenges of traditional chip scaling, two-dimensional (2D) materials turn out to be ideal candidates for incorporation into semiconductor devices. Therefore, a method to efficiently locate defects and grain boundaries in 2D materials is highly essential.

Synthesis and properties of MoCl complexes with thio- and seleno-ethers and their use for chemical vapour deposition of MoSe and MoS films.

Treatment of trans-[MoCl(MeCN)] with L (L = MeS, MeSe, THT, ½MeSCHCHSMe) in CHCl solution, or reaction of MoCl with excess L' (L' = BuS, BuSe, ½MeSCHCHSMe, ½PrSCHCHSPr, ½MeSCHCHCHSMe, ½MeSeCHCHCHSeMe) in MeCN, produces the Mo(iv) complexes, [MoCl(L)] and [MoCl(L')], respectively, in good yield. The new complexes have been characterised by IR and UV-vis spectroscopy, elemental analysis and magnetic measurements, whilst crystal structure analyses of trans-[MoCl(MeS)], cis-[MoCl{RS(CH)SR}] (R = Me, Pr) and cis-[MoCl{MeS(CH)SMe}] confirmed their identities and distorted octahedral geometries. The potential of [MoCl(BuE)] (E = S, Se) as the first examples of molybdenum halide derived single source CVD precursors for the growth of MoE thin films was first probed by TGA, which showed multi-step decomposition processes, with the masses of the final residues consistent with MoSe (E = Se) and MoCl (E = S), respectively.

Chalcogenoether complexes of Nb(v) thio- and seleno-halides as single source precursors for low pressure chemical vapour deposition of NbS and NbSe thin films.

NbSCl was obtained via reaction of NbCl with S(SiMe) in anhydrous CHCl, whilst in MeCN solution the same reaction gives [NbSCl(MeCN)]. [NbSeCl(MeCN)] was obtained similarly from NbCl with Se(SiMe). The chalcogenoether complexes, [NbSCl(ER)] (E = S: R = Me, Bu; E = Se: R = Bu), were obtained from reaction of NbCl, ER and S(SiMe) in CHCl.

Developments in the chemistry of the hard early metals (Groups 1-6) with thioether, selenoether and telluroether ligands.

The coordination chemistry of neutral thio-, seleno- and telluroether ligands towards the hard s-block, f-block and higher oxidation state early d-block metals has developed significantly over the last 15 or so years. This has revealed several hitherto unknown classes of complexes and new insights into the chemistries of these hard-soft metal-ligand combinations. This Perspective describes the synthetic routes used to access such complexes and draws out their key structural features and spectroscopic properties.

Niobium tetrachloride complexes with thio-, seleno- and telluro-ether coordination - synthesis and structures.

NbCl reacts with the dithioethers MeS(CH)SMe (n = 2 or 3), PrS(CH)SPr or o-CH(CHSEt) in a 1 : 1 molar ratio in CHCl or toluene over several days, to give red or orange, paramagnetic complexes, [NbCl(dithioether)]. Their X-ray crystal structures confirm distorted octahedral geometries with chelating dithioether. MeS(CH)SMe, alone, also forms an [NbCl{MeS(CH)SMe}] complex based upon eight-coordinate Nb(iv) in a square antiprismatic geometry.

Niobium(V) and tantalum(V) halide chalcogenoether complexes--towards single source CVD precursors for MEâ‚‚ thin films.

A series of pentavalent niobium and tantalum halide complexes with thio-, seleno- and telluro-ether ligands, [MCl5(E(n)Bu2)] (M = Nb, Ta; E = S, Se, Te), [TaX5(TeMe2)] (X = Cl, Br, F) and the dinuclear [(MCl5)2{o-C6H4(CH2SEt)2}] (M = Nb, Ta), has been prepared and characterised by IR, (1)H, (13)C{(1)H}, (77)Se, (93)Nb and (125)Te NMR spectroscopy, as appropriate, and microanalyses. Confirmation of the tantalum(V)-telluroether coordination follows from the crystal structure of [TaCl5(TeMe2)], which represents the highest oxidation state transition metal complex with telluroether coordination structurally authenticated. The Ta(V) monotelluroether complexes are much more stable than the Nb(V) analogues.