Search

Homoleptic zinc(II) and cadmium(II) complexes containing hybrid N-selenophosphinoylchalcogenoureato ligands, [M(iPr2P(Se)NC(X)NC5H10-κ2-Se,X)2] (M = Zn, X = S (3), X = O (4) and M = Cd, X = S (5)) and [Cd(iPr2P(Se)NC(O)NC5H10)2-μ-O,O]2 (6), were synthesized and characterized by elemental analysis, IR and NMR spectroscopy. SCXRD molecular structures of complexes revealed bidentate ligands bonded to the metal center in a distorted tetrahedral coordination geometry for 4 and 5, while 6 exhibited a dinuclear centrosymmetric structure with a distorted trigonal bipyramidal coordination. Based on thermogravimetric analysis (TGA), the complexes (3–6) were tested as single source precursors (SSPs) to prepare metal chalcogenide thin films by aerosol-assisted chemical vapor deposition (AACVD) at 450 °C (annealing at 600 °C) and 375 °C. 4 and 6 produced good quality hexagonal MSe thin films (4F and 6F), while, remarkably, 3 and 5 deposited the corresponding ternary hexagonal MSSe thin films (3F and 5F) with S contents of 15.8% for 3F and 1.8% for 5F (EDXA). This was confirmed by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDXA), from which the elemental composition was also determined. The as-deposited thin films displayed a phosphorus content between 2.0 and 4.4%, while zinc-containing precursors produced zinc-rich thin films. The surface morphologies of 3F–6F were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM), showing quasi-spherical particles in columns. The optical properties suggest good crystalline quality of as-deposited thin films. The band gaps (Eg) of MSSe films were higher than those of MSe materials. PL spectra of Cd-containing films showed a dominant emission band with a maximum between 1.69 and 1.76 eV related to near-band-edge (NBE) emission, while Zn-containing films showed broad PL signals at ca. 2.0–2.4 eV that could be associated with structural defects. All Raman spectra showed multiple LO phonon overtones, and MSSe solid solutions (from 3 and 5) showed both expected LO scattering modes (MSe-like and MS-like phonons). [ABSTRACT FROM AUTHOR]

Zinc(II) and cadmium(II) complexes of general formula [M(iPr2P(X)NC(Y)NC5H10-κ2-X,Y)2] (M = Zn, X = Y = S (4), X = S, Y = O (5), X = O, Y = S (6), and M= Cd, X = Y = S (7), X = S, Y = O (8), X = O, Y = S (9)) have been synthesized and characterized by using elemental analysis, IR and NMR spectroscopy, and thermogravimetric analysis (TGA). SCXRD molecular structures of complexes 6, 7, and 9 revealed ligand binding to the metal center in a bidentate fashion in an overall distorted tetrahedral coordination geometry. TGA showed that 4–9 decompose in a single step to their corresponding metal sulfides. Aerosol assisted chemical vapor deposition (AACVD) at 450 °C and subsequent annealing at 600 °C were used to examine 4–9 as single source precursors (SSPs) for the deposition of nanostructured metal sulfide thin films (4F–6F unannealed ZnS films and 7F–9F unannealed CdS films). GIXRD confirmed that the resultant films have a nanocrystalline hexagonal structure with the (002) preferential orientation, except for 9F, and the grain size varied from 15 to 24 nm. Scanning electron microscopy and atomic force microscopy (SEM and AFM) images revealed a relatively dense grain columnar structure. The elemental composition and mapping studies showed that the near-stoichiometric MS thin films are homogeneously distributed. The as-deposited ZnS thin films (4F–6F) displayed phosphorus content between 6.4 and 8.2%, while CdS films showed no phosphorus content except for 9F, which showed P 2%. The optical properties of the films such as direct optical energy gap (Eg), and Raman and photoluminescence (PL) spectra displayed some differences related to the employed SSP, being more significant for films obtained from precursors containing the hybrid ligand –P(O)NC(S)– (3), which showed a major phosphorus content (6F and 9F). A sharp excitonic emission at room temperature, as well as multiple Raman overtones, shows the high optical quality of the investigated CdS thin films. The PL spectra of ZnS films showed emissions attributed to the near band edge and different crystalline imperfections such as vacancies and interstitials. [ABSTRACT FROM AUTHOR]