RESUMO
High-quality lead sulfide (PbS) films are deposited on selected substrate chemistries by an H2 S-free metal-organic chemical vapor deposition (MOCVD) process using a single-source metal-organic complex (Pb(dmampS)2 ). The complex is synthesized via a salt metathesis reaction between PbCl2 and lithium 1-(dimethylamino)-2-methylpropane-2-thiolate (Li(dmampS)) in diethyl ether. Subsequent film deposition is conducted by a simple thermolysis process in the absence of H2 S, yet chemical and structural analysis confirm chemically stoichiometric and homogenous films. Mechanistic studies with electron impact mass spectroscopy (EIMS) and gas chromatography mass spectroscopy (GCMS) suggest the selective cleavage of C-S bonds in the complex as the reason for the facile PbS formation with negligible impurity incorporation. The high crystallinity, low hole concentrations, and charge transport properties comparable and in many cases superior to films produced by atomic layer deposition (ALD) testify to the quality of the films. Lastly, rigid and flexible photodetectors fabricated with the PbS films exhibit considerably high photocurrents, reliable switching characteristics, and high sensitivity over a broad spectral bandwidth, highlighting the potential for realizing practical broadband photodetectors.
RESUMO
A new heteroleptic complex series of tin was synthesized by the salt metathesis reaction of SnX2 (X = Cl, Br, and I) with aminoalkoxide and various N-alkoxy-functionalized carboxamide ligands. The complexes, [ClSn(dmamp)]2 (1), [BrSn(dmamp)]2 (2), and [ISn(dmamp)]2 (3), were prepared from the salt metathesis reaction of SnX2 with one equivalent of dmamp; [Sn(dmamp)(empa)]2 (4), [Sn(dmamp)(mdpa)]2 (5), and [Sn(dmamp)(edpa)]2 (6) were prepared via the salt metathesis reaction using complex 2 with one equivalent of N-alkoxy-functionalized carboxamide ligand. Complexes 1-5 displayed dimeric molecular structures with tin metal centers interconnected by µ2-O bonding via the alkoxy oxygen atom. The molecular structures of complexes 1-5 showed distorted trigonal bipyramidal geometries with lone pair electrons in the equatorial position. Using complex 6 as a tin precursor, SnO x films were deposited by chemical solution deposition (CSD) and subsequent post-deposition annealing (PDA) at high temperatures. SnO and SnO2 films were selectively obtained under controlled PDA atmospheres of argon and oxygen, respectively. The SnO films featured a tetragonal romarchite structure with high crystallinity and a preferred growth orientation along the (101) plane. They also exhibited a lower transmittance of >52% at 400 nm due to an optical band gap of 2.9 eV. In contrast, the SnO2 films exhibited a tetragonal cassiterite crystal structure and an extremely high transmittance of >97% at 400 nm was observed with an optical band gap of 3.6 eV.
RESUMO
A novel series of zinc complexes, [EtZn(dab)]2 (1), [EtZn(damb)]2 (2), [EtZn(damp)]2 (3), and [EtZn(dadb)]2 (4), were prepared via single-step substitution. Further, these were analyzed by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, single crystal X-ray diffraction analysis, and thermogravimetric analysis (TGA). The X-ray crystallography analysis revealed that all complexes exist as dimeric structures with distorted tetrahedral geometry having zinc centers that are interconnected via µ2-O bonding of the aminoalkoxy oxygen atom. TGA and thermal analysis of the complexes showed high volatilities and stabilities at sublimation temperatures of 70, 95, 90, and 105 °C at 0.5 Torr for the respective compounds. Precursor 3 was successfully used for ZnO thin film deposition by ALD. A growth rate per cycle (GPC) of 0.125 nm per cycle was obtained at 200 °C and XPS analysis confirmed the growth of highly pure ZnO films without carbon and nitrogen impurities, while XRD analysis revealed the deposition of reasonably crystalline films. Additionally, the high transmittance and wide bandgap of the films are suitable for optoelectronic applications.