Disiloxane-Bridged Cyclopolymer as Polymer Dielectrics

We studied the dielectric properties of organosilicon-containing helical cyclopolymer PbMA which consists of PMMA main chains and tetramethyldisiloxane side rings. PbMA formed films with excellent uniformity through spin-coating onto highly n-doped silicon (n-Si) wafers for constructing devices of dielectric measurements, on which the dielectric properties and I-V characteristics of PbMA were studied. PbMA has a much lower dielectric constant (lower than 2.6) in the frequency range of 10-10⁵ Hz, and better thermal stability than PMMA does. I-V data showed that the metal/PbMA/n-Si devices have different conducting directions, depending on whether Au or Al deposited over PbMA layers.     

Polymer concentration, shear and stretch field effects on the surface morphology evolution during the spin-coating

Polymer concentration and shear and stretch field effects on the surface morphology evolution of three different kinds of polymers (polystyrene (PS), polybutadiene (PB) and polystyrene-b-polybutadiene-b-polystyrene (SBS)) during the spin-coating were investigated by means of atomic force microscopy (AFM). For PS and SBS, continuous film, net-like structure and particle structure were observed at different concentrations. For PB, net-like structures were not observed and continuous films and radial array of droplets emerged. Moreover, we compared surface morphology transitions on different substrate locations from the center to the edge. For PS, net-like structure, broken net-like structure and irregular array of particles were observed. For SBS, net-like structure, periodically orientated string-like structure and broken-line structure appeared. But for PB, flower-like holes in the continuous film, distorted stream-like structure and irregular distributions of droplets emerged. These different transitions of surface morphologies were discussed in terms of individual material property.     

Thermal diffusivity measurement of low-k dielectric thin film by temperature wave analysis

Thermal diffusivity of thin film with low dielectric constant (k), what is called low-k dielectric thin film, 0.31-1.14 μm, including hydrogen-silsesquioxane (HSQ), methyl-silsesquioxane (MSQ), and poly(arylen ether) was examined by temperature wave analysis. The phase shift of temperature wave was observable up to 100 kHz. Thermal diffusivity of HSQ was 4.7 × 10⁻⁷ m² s⁻¹, on the other hand it was not higher than 1.1 × 10⁻⁷ m² s⁻¹ for MSQ or poly(arylen ether) at room temperature. Temperature dependence of thermal diffusivity/thermal conductivity of MSQ was obtained, thermal diffusivity decreased but thermal conductivity increased in a heating scan at 30-150 °C. It was shown that the thermal diffusivity of low-k thin film was correlated with the chemical and the physical structures, the latter was formed in the spin-coating and the curing process.     

用于聚合物介电材料的双硅氧烷链接的环化聚合物

We studied the dielectric properties of organosilicon-containing helical cyclopolymer PbMA which consists of PMMA main chains and tetramethyldisiloxane side rings. PbMA formed films with excellent uniformity through spin-coating onto highly n-doped silicon (n-Si) wafers for constructing devices of dielectric measurements, on which the dielectric properties and I-V characteristics of PbMA were studied. PbMA has a much lower dielectric constant (lower than 2.6) in the frequency range of 10-10⁵ Hz, and better thermal stability than PMMA does. I-V data showed that the metal/PbMA/n-Si devices have different conducting directions, depending on whether Au or Al deposited over PbMA layers.     

Probing phase formation and structural ordering in Ba3ZnNb2O9 films using confocal Raman microscopy

In this paper we investigated the phase formation and structural ordering in spin-coated Ba₃ZnNb₂O₉ perovskite films using confocal Raman microscopy. The films were deposited through polyester resins obtained from a polymeric precursor. Initially, the films were characterized by X-ray diffraction and atomic force microscopy. Raman spectroscopy confirmed the crystalline structure of the main phase, as well as its partially disordered feature. Raman mappings were employed to probe the secondary phase distribution in the films, and to determine the calcining time-dependent film thicknesses.     

Inorganic-organic Hybrid Structured LED's

Three-layered heterocontact light emitting diodes (LED's) were generated by spin-coating processes. Perovskites of the type [C₆H₅(CH₃)CHNH₃]₂PbX₄ (X = Cl, Br) on ITO glass served as p-semiconductors, while 1,3,5-[5-(4-tert-butylphenyl)-2-oxadiazyl]benzene (Starburst) in polystyrene was selected as the organic n-semiconductor. As a zone for the electron-hole recombination between p- and n-semiconductor layer a poly(N-vinylcarbazole)-layer, doped with 3-(2-benzothiazolyl)-7-diethylamino-coumarin (Coumarin6), as emitter molecule was used. A Mg : Ag electrode served as the cathode on the Starburst : polystyrene blend. Both diodes showed green luminescence at 7 V. The external quantum yield of the diode with the PbCl₄^2– perovskite was 0.4%, but only 0.06% for PbBr₄^2–. This is due to the different band structures of the layered perovskites.     

The role of photoinitiator and chelating agent in the fabrication of optical waveguides from UV-photocurable organo-mineral sol-gel materials

This work focuses on the role of photoinitiators and chelating agents in waveguide fabrication based on UV sensitive sol-gel materials. The key role that a photoinitiator plays in waveguide formation has been shown through examination of waveguide width and cross-sectional shape. Waveguides fabricated using Irgacure-907 were found to be on average 2.5 times wider at the top surface than those fabricated using Irgacure-819 or -1800. UV-Vis measurements on the photoinitiators confirmed that Irgacure-907 is approximately 35 times more absorbing than the other photoinitiators at the UV exposure wavelength of 325 nm. This has been found to give rise to a highly trapezoidal waveguide shape which, also affects waveguide adhesion. The influence of the chelating agent within the hybrid sol has also been studied with reference to waveguide width. These experiments clearly showed that the Zr(OPr)₄ molecule plays an active role in the photopolymerization process, and its activity is controlled by its degree of chelation. Two different chelating agents, methacrylic acid (MAAH) and isobutyric acid (IBA) were compared. The trend for both chelating agents was the same, but IBA chelated sols resulted in narrower waveguides. This has been attributed to the higher steric hindrance of IBA compared to MAAH, which would inhibit the propagation of polymerization in the coating.     

右旋聚乳酸薄膜的结晶形态

利用旋涂法制备一系列右旋聚乳酸(PDLA)均聚物薄膜, 在不同溶液浓度、结晶温度、结晶时间、溶剂和基底条件下对其进行等温结晶处理, 得到直径和长度大小不等的短棒和纤维束球状等形态, 利用原子力显微镜(AFM)研究了不同条件下所得到的PDLA薄膜的结晶形态. 提出了可能的结晶演变过程和生长模型. 通过控制不同的结晶条件, 可以得到PDLA均聚物薄膜的不同结晶形态.     

Synthesis and characterization of new mesomorphic octakis(alkylthio)-substituted lead phthalocyanines and their films

The syntheses of new octakis (alkylthio)-substituted phthalocyanines of Pb(II) (1a and 2a) are described. These compounds are very soluble in most common organic solvents. They have been fully characterized using elemental analysis, NMR, infrared and UV–Vis spectroscopy. The mesogenic properties of these new materials were studied by differential scanning calorimetry and optical microscopy. These phthalocyanine derivatives are liquid at room temperature and form columnar-hexagonal (Col_h) mesophases below −10 °C. It has been indicated that the addition of methylene bridges to the phthalocyanine (Pc) core increases the clearing point temperatures. Also, the coordination of Pb²⁺ with the phthalocyanine core decreases the clearing point temperatures and the liquid crystal phase transition temperatures. Thin films of octakis(alkylthio)-substituted Pb(II) phthalocyanines 1a and 2a were prepared by the method of spin-coating. To obtain films with an ordered structure the film of 1a was slowly cooled from room temperature down to −10 °C. Sandwich structures of the form Au/PbPc(1a)/Au were prepared for the investigation of their electrical properties. It was shown that a slowly cooled Au/PbPc(1a)/Au structure demonstrates repeatable and stable electrical switching behaviour for applied bias voltages between −1 V and +1 V.     

Synthesis, spectral, and thermal characterizations of Ni(II) and Cu(II) beta-diketone complexes with thenoyltrifluoroacetone ligand

Two kinds of nickel(II) and copper(II) beta-diketone complexes derived from thenoyltrifluoroacetone ligand with blue-violet light absorption were synthesized by reacting free ligand and different metal(II) ions in sodium methoxide solution. Their structures were postulated based on elemental analysis, ESI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films on K9 glass substrates were prepared using the spin-coating method. Their solubility in organic solvents, absorption properties of thin film and thermal stability of these complexes were evaluated.