Mononuclear precursor for MOCVD of HfO2 thin films

We report the precursor characteristics of a novel mononuclear mixed alkoxide compound [Hf(O(i)Pr)2(tbaoac)2] and its application towards MOCVD of HfO2 thin films in a production tool CVD reactor.     

A urea adduct of bis(hinokitiolato)copper(II)

Bis(μ₂‐3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)bis[(3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)copper(II)]–urea–acetone (1/6/2), [Cu₂(C₁₀H₁₁O₂)₄]·6CH₄N₂O·2C₃H₆O, where 3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olate is the systematic name for the hinokitiolate anion, contains three novel structural features. First, it contains a bis(hinokitiolato)copper(II) dimer, [Cu(hino)₂]₂, unlike any other, demonstrating that linkage isomerism is another avenue by which Cu(hino)₂ can transmute from one form to another. Second, [Cu(hino)₂]₂ is hydrogen bonded to two urea molecules, indicating that hydrogen bonding cannot yet be discounted from any proposed mechanism of action for the antimicrobial and antiviral properties of bis(hinokitiolato)copper(II). Finally, corrugated urea layers crosslinked by [Cu(hino)₂]₂ dimers are observed, suggesting that a new family of host–guest materials, i.e. metallo–urea clathrates, exists to challenge our understanding of crystal engineering and crystal growth and design. Selected details of the structure are that the [Cu(hino)₂]₂ dimers possess crystallographic inversion symmetry, the Cu atoms have square‐pyramidal coordination geometries, the basal Cu—O bonds are in the range 1.916 (2)–1.931 (2) Å, the apical Cu—O bond length is 2.582 (2) Å, the hinokitiolate bite angles are in the range 83.41 (7)–83.96 (8)°, the urea–Cu(hino)₂ interactions have an R₂²(8) motif, and the urea layers result from the close packing of R₈⁶(28) `butterflies' and R<sub>8</sub><sup>6</sup>(24) `strips of tape'.     

A novel single source precursor: [bis(N,N-diethyl-N'-naphthoyl-selenoureato)palladium(II)] for palladium selenide thin films and nanoparticles

We describe for the first time the use of a single source precursor to deposit thin films and nanocrystals of palladium selenide.     

Preparation and properties of solution-processed zinc tin oxide films from a new organic precursor

Transparent,smooth and dense zinc tin oxide (ZTO) thin films have been successfully produced by using a new precursor solution,zinc acetate and tin(II) 2-ethylhexanoate mixed with 2-ethanolamine in methoxyethanol.The ZTO films have been prepared by spin-coating,followed by thermal treatment in oxygen atmosphere.The morphology,composition,crystallinity and band gap energy (Eg) of the ZTO thin films have been characterized by Atomic Force Microscopy (AFM),Atomic Emission Spectrometry (AES),X-ray Diffraction (...     

Organic–inorganic nanocomposites of (2‐hydroxypropyl)cellulose as a precursor of nanocrystalline zinc oxide layers

The sol–gel method of synthesis of the hybrid nanocomposite films of ZnO/(2‐hydroxypropyl) cellulose (HPC) on silica glass is presented. The sol phases were prepared for different weight ratios of zinc acetate dihydrate to HPC in the presence of triethylamine (TEA). Raman spectrum of the mixture of ZnAc and HPC indicates coordinating interaction between zinc ion and HPC. The generation of ZnO nanoparticles in the HPC matrix proceeds in situ through the annealing of the gel phase at a temperature of 160°C. Identification of ZnO nanoparticles in the HPC matrix is done by using photoluminescence (PL), UV–Vis, and Raman spectroscopy. The films of ZnO/HPC nanocomposite are transparent in the visible light and show a higher energy value of absorption edge compared with ZnO in the bulk. Nanocrystalline films of ZnO were obtained by the calcination of ZnO/HPC nanocomposite at 500°C. ZnO films possess a good transparency for the visible light and high absorbance for UV light. Nanocrystallite sizes of ZnO particles were estimated from the X‐ ray lines broadening. The properties of ZnO layers were studied by the evaluation of PL, X‐ray investigation and atom force microscope (AFM) scanning, and the optical absorption edge. Copyright © 2008 John Wiley & Sons, Ltd.     

Guanidinate-stabilized monomeric hafnium amide complexes as promising precursors for MOCVD of HfO2

Novel guanidinato complexes of hafnium [Hf{eta2-(iPrN)2CNR2}2(NR2)2] (R2 = Et2, 1; Et, Me, 2; Me2, 3), synthesized by insertion reactions of N,N'-diisopropylcarbodiimide into the M-N bonds of homologous hafnium amide complexes 1-3 and {[mu2-NC(NMe2)2][NC(NMe2)2]2HfCl}2 (4) using a salt metathesis reaction, are reported. Single-crystal X-ray diffraction analysis revealed that compounds 1-3 were monomers, while compound 4 was found to be a dimer. The observed fluxional behavior of compounds 1-3 was studied in detail using variable-temperature and two-dimensional NMR techniques. The thermal characteristics of compounds 1-3 seem promising for HfO2 thin films by vapor deposition techniques. Metal-organic chemical vapor deposition experiments with compound 2 as the precursor resulted in smooth, uniform, and stoichiometric HfO2 thin films at relatively low deposition temperatures. The basic properties of HfO2 thin films were characterized in some detail.     

Cyclodextrin inclusion complexes as novel MOCVD precursors for potential cobalt oxide deposition

The potential use of the inclusion complexes of β‐cyclodextrins with metal halides as novel precursors in MOCVD applications was examined in terms of microstructure, thermal stability and chemical modifications during heating. The investigation was especially focused on the inclusion complex of β‐cyclodextrin with cobalt iodide for cobalt oxide thin film deposition. The general composition assigned to the dextrin's inclusion complex was: (β‐CD)₂^?CoI₇^?11H₂O. It was found that the inclusion complex of β‐cyclodextrin with CoI₂ may prove a promising alternative to traditional metalorganic or organometallic Co‐precursors for precise CVD applications. The sublimation temperature must be preferably in the range 70–125 °C, and the decomposition temperature (substrate temperature) in the range of 350–400 °C. Three distinct regions can be recognized by heating: transformation of tightly bound water molecules into easily movable ones, sublimation of iodine ions and Co atoms oscillation and thermal decomposition of the glycositic ring into volatile by‐products. Copyright © 2009 John Wiley & Sons, Ltd.     

PVC-based bis(2-nitrophenyl)disulfide sensor for zinc ions

A PVC membrane electrode based on bis(2-nitrophenyl)disulfide carrier exhibits a very good response for Zn²⁺ in a wide concentration range (from 2.9×10⁻⁷ to 3.2×10⁻² mol l⁻¹) with a slope of 29.9±0.4 mV per decade of Zn²⁺ concentration. The response time of the sensor is about 10 s and the membrane can be used for more than 3 months without any observed divergence in potentials. The proposed sensor exhibits very good selectivity for Zn²⁺ over many cations and can be used in a wide pH range (2-9). This assembly served also as an indicator electrode in potentiometric titrations involving zinc ions and direct potentiometric determination of zinc ions in real and synthetic samples.     

Mercury bis(phenyltellurolate) as a precursor for the synthesis of binary and ternary nanoclusters

The reaction of Hg(TePh)2 with AgX (X = Cl, NO3) in the presence of PPh3 and PMePh2 in dimethylformamide (DMF) affords the cluster [Hg6Ag4(TePh)16] (1) at room temperature or [Hg6Ag4Te(TePh)14]2 (2) with heating. When Hg(TePh)2 is reacted with [Co(PPh3)2Cl2] or [Ni(PPh3)2Cl2], the clusters [Hg8Te(PhTe)12Cl4]Q [3; Q = [Co(DMF)6]2+ (3a), [Ni(DMF)6]2+ (3b)] are formed. The syntheses of 1 and 2 occur with the incorporation of AgI into the cluster, and the single-crystal analyses show that the two ternary clusters consist of Hg, Ag, and Te centers occupying well-defined positions. Compounds 3a and 3b do not show the incorporation of the metal into the cluster, but the CoII and NiII salts provide the Cl atom to generate the anionic cluster 3 stabilized by the [Co(DMF)6]2+ or [Ni(DMF)6]2+ ion.     

Synthesis and characterization of zinc bis(O‐isopropylxanthate) as a single‐source chemical vapor deposition precursor for ZnS

The utilization of single‐source molecular precursors in chemical vapor deposition (CVD) experiments requires a deep knowledge of their chemico‐physical properties, with particular regard to thermal stability and fragmentation pattern. This study describes the synthesis and characterization of zinc bis(O‐isopropylxanthate), Zn(O‐ⁱPrXan)₂, [O‐ⁱPrXan = (CH₃)₂CHOCS₂], a single‐source precursor for the CVD of zinc(II) sulfide thin films and nanorods. Several analytical methods yielding complementary information (extended X‐ray absorption fine structure, Raman, FT‐IR, UV–Vis optical absorption, ¹H and ¹³C NMR, thermogravimetric analysis, differential scanning calorimetry as well as mass spectrometry techniques, i.e. electrospray and electron ionization, mass‐analyzed ion kinetic energy) are adopted for a comprehensive investigation of purity, structure, thermal behavior and decomposition pathways of the molecule. The most significant results are discussed critically and the properties useful for CVD applications are highlighted. Copyright © 2005 John Wiley & Sons, Ltd.     

3,8,11,16-Tetrakis(aminomethyl)-1,2,9,10-tetrathia-cyclohexadecane tetra-trifluoroacetic acid: synthetic precursor to a novel thio-substituted diamine

Diamines have proven to be versatile intermediates in organic chemistry. Few diamines, however, can be appended to organic and inorganic supports without modification of the diamine functionality. We report the synthesis of 3,8,11,16-tetrakis-(N-BOC-aminomethyl)-1,2,9,10-tetrathia-cyclohexadecane (2) and 3,8,11,16-tetrakis(aminomethyl)-1,2,9,10-tetrathia-cyclohexadecane tetra-trifluoroacetic acid (3), potential precursors to 1,8-diamino-2,7-octanedithiol (4). Incorporation of the thiol units within the diamine backbone of 4 permits this compound to attach to organic and inorganic scaffolds. Spectral and chemical data showed that base hydrolysis of 1,8-bis(N-BOC-amino)-2,7-bis(acetylthio)octane (16) produced the 16-membered bis-disulfide 2 rather than the 8-membered ring dithiocane 17.     

Polycondensation of bis(p-nitrophenyl) β-truxinate with diamine

Model reaction of bis(4-nitrophenyl) β-truxinate (BNPT) with aliphatic amines proceeded quantitatively at room temperature. Accordingly, polycondensation of BNPT with various diamines was carried out at room temperature or 80°C. During the polycondensation of BNPT with diamines, the precipitation of polymer or the observed gelation of polymerization solution occurred, which may limit the molecular weight of the polymer. On the other hand, the reaction of BNPT with 1,3-(4-piperidyl)propane (DPP) proceeded homogeneously to give the polymer with relatively high molecular weight, and the obtained polyamide (P-1e) showed excellent solubility in many solvents. The study of TG and DTA indicated that the obtained polymers were stable at lower temperature than around 270°C. The polymer prepared from the polycondensation of BNPT with hexamethylenediamine showed melting point and decomposition due to the imidation at 282°C. The photochemical reaction of these polymers was carried out in the film state. The irradiation of 254 nm light caused an absorption at 272 nm to appear and the molecular weight to decrease. This meant that the scission of cyclobutane ring in the main chain occurred to give cinnamamide structures. Also, the absorption at 272 nm decreased by the irradiation of 302.5 nm light. However, the UV spectrum of irradiated polymer did not agree with that of the original polymer. These results suggested that the dimerization of the resulting cinnamamide moieties occurred in the competition of their trans–cis-isomerization. On the other hand, the rate of scission of cyclobutane ring of P-1e was faster than that of the corresponding polyamide containing α-truxillamide structure.     

Preparation of poly(bis(trialkylammonium) 4,4′-oxydiphenylenepyromellitamate) films: A useful polyimide precursor film

A poly[bis(trialkylammonium) 4,4′-oxydiphenylenepyromellitamate] film not containing residual solvents was prepared first as a polyimide precursor film. The preparative method is composed of three process steps involving (1) polymerization of pyromellitic dianhydride with 4,4′-oxydianiline in a mixed solvent of tetrahydrofuran/methanol, (2) addition of a mixture of methanol/trialkylamine to the resulting poly(4,4′-oxydiphenylenepyromellitamic acid) solution, and (3) casting onto glass plates and drying. The salt formation between the poly(amic acid) and trialkylamines was confirmed first by spectroscopic methods. The dried salt film is thermally cured to produce the polyimide film with a reduced coefficient of thermal expansion (CTE). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2493–2499, 1997     

A novel C(2)-symmetric 2,6-diallylpiperidine carboxylic acid methyl ester as a promising chiral building block for piperidine-related alkaloids

C(2)-symmetric 2,6-diallylpiperidine 1-carboxylic acid methyl ester (5) was examined via the double asymmetric allylboration of glutaraldehyde followed by aminocyclization and carbamation as a promising chiral building block for piperidine-related alkaloids, which were synthesized by the desymmetrization of 5 using intramolecular iodocarbamation as a key step. [reaction: see text]     

Electroninitiated polymerization of bis(trichlorophenoxo)-tetramethylethylene diamine copper(II)

Electroninitiated polymerization of bis(trichlorophenoxo)-N,N,N′,N′-tetramethylethylene diamine copper(II) was achieved in acetonitrile at various peak potentials of the monomer. A constant potential approach was selected in polymerization reactions. Electrolyses were carried out under air, nitrogen, and oxygen atmospheres. Structural analyses of the polymers were done by ¹H-NMR and ¹³C-NMR FT–IR spectroscopy. Molecular weights of the polymers were determined by vapor pressure (isopiestic) method.