A hexane solution deposition of SnS2 films from tetrabutyltin via a solvothermal route at moderate temperature

SnS₂ films have been deposited on glass and alumina plate substrates by the reactions between an organotin precursor [tetrabuyltin, (CH₂CH₂CH₂CH₃)₄Sn] and carbon disulfide in n-hexane at the temperature range 180-200 °C for 10-40 h. The reaction system was oxygen free and applied at a moderate temperature. The films so prepared were characterized by techniques of X-ray diffraction, Scanning electron microscopy, Raman and Mössbauer spectroscopies. The films deposited on glass as well as on alumina plate have an average thickness of 30 μm, but have different rose-like morphologies, which are influenced by both the anisotropic growths of crystals and the different substrate structures. Photoluminescence measurements show that the films have an emission peak at approximately 590 nm.     

Control of polymerization processes of 10,12-pentacosadiynoic acid LB films

Studies have been carried out on KrF excimer laser light (EX), X-ray or electron beam (EB) induced polymerization of 10,12-pentacosadiynoic acid (PDA) Langmuir-Blodgett (LB) films in relation to molecular density or molecular arrangement of the films using X-ray diffraction analysis, infrared (IR) spectroscopy and Raman spectroscopy. The molecular arrangement or density of the PDA LB films was controlled by subphase conditions when the films were built up, such as pH, temperature of a subphase or salt concentration in the subphase. Polymerization sensitivity of the PDA LB film was affected by the arrangement or molecular density. On low density (A type) films the polymerization occurred by irradiation with EX, X-ray or EB, but on high density (B type) films the polymerization occurred only when the irradiation was carried out by high energy beams such as X-ray or EB. Decomposition of polymerized films was observed further by excessive irradiation of EX or X-ray, but not on the B type films. It was revealed by X-ray diffraction analysis that in the A type film, the PDA molecules bent to a larger extent than those in the B type film and the polymerization proceeded topochemically, that is, the thickness decreased little after EB irradiation in a helium atmosphere. On the other hand, in the B type film, the thickness decreased by about 10% as a result of EB irradiation. By IR reflection-absorption (RA) and Raman measurements, it was confirmed that conjugated diacetylenic bonds disappeared and conjugated double and new conjugated triple bonds appeared after high energy beam irradiations. These results support the supposition that 1,4-polymerization, i.e. polydiacetylene type polymerization, occurs easily in the A type film and 1,2- or 3,4-polymerization, i.e. polyacetylene type polymerization, occurs in the B type film, and that the polymerized A type film was decomposed at the polydiacetylenic bond when the irradiation continued further. It was also shown that the polyacetylene type polymer was obtained only when the B type film was irradiated with the high energy beam.     

Possible tactics to improve the growth of single-walled carbon nanotubes by chemical vapor deposition

The growth time, growth mode and the method of preparing the supported catalysts play an important role in the growth of single-walled nanotubes (SWNTs). Their effects on the chemical vapor deposition (CVD) growth of SWNTs with MgO-supported catalysts were investigated in this study. It is shown that the growth rate of SWNTs was large during the initial few minutes of growth, however the quality of the tubes was low owing to the formation of many defects. Long term growth may favor the formation of tubes with high quality and high yield, but the introduction of other forms of carbon (impurities) is also unavoidable. There was a balance between the increase in yield and quality and sacrifice of the purity during growth of SWNTs. MgO-supported catalysts prepared by the co-precipitation method were found to be more effective for the synthesis of SWNTs than those prepared by the widely used impregnation method. The size and dispersion state of the catalyst were found to be crucial in enhancing the growth of SWNTs. In addition, growth on the surface of SWNTs over nanosized catalyst films was shown to be more favorable for the synthesis of tube products with higher quality, yield and purity.     

四倍频Nd：YAG激光在高压氢气中的喇曼频移研究

利用Nd:YAG固体激光器四倍频输出(266nm)在高压H₂中的受激喇曼散射获得多波长的激光输出。当泵浦能量一定时,通过改变H₂压力得到了最佳的能量输出,299nm波长的激光能量为3mJ,341nm波长的激光能量输出为6.1mJ,398nm波长的激光能量输出为2.8mJ,239nm波长的激光能量输出为0.8mJ,同时在477nm,595nm,218nm,200nm波段也有能量输出。     

Temperature Dependence of the Raman Spectrum in Lithium Oxide Single Crystal

Temperature dependence of the Raman spectrum of lithium oxide single crystal has been measured over a temperature range of 80 to 1073 K. The frequency shift and the line width of the Raman spectrum in lithium oxide were about 531 and 4.5 cm^-1 at 80 K, respectively. At 1073 K, the frequency shift and the line width attained the values of 464 and 112 cm^-1, respectively. The strong temperature dependence of the frequency shift and line width was compared with data from some crystals with a fluorite structure.     

Infra-red and Raman spectroscopic study on the thermal stability and high temperature transformation of hydroazafullerene C59HN

Hydroazafullerene C₅₉HN was studied by vibrational infra-red and Raman spectroscopy and its thermal stability was examined. Fingerprints modes were identified and unambiguously differentiate it from bisazafullerene. At 700 K full transformation to bisazafullerene occurred, while an intermediate metastable phase was identified at 540 K showing different spectra where the splitting of most of the lines is strongly reduced.     

Correlation of vibrational intensity with fluorescence lifetimes in π conjugated polymers

A series of novel pi (π) conjugated polymers, originating from the archetypical Polyphenylene vinylene, in which the phenyl units are successively replaced by the larger naphthyl and anthryl acene units, were previously found to have a well-defined relationship between their relative fluorescence yields and their vibrational characteristics, as determined by Raman spectroscopy. In this study the Strickler-Berg equation is used to probe the influence of continual substitution of higher order acene units into the conjugated backbone in terms of the variation of the radiative and non-radiative rates. The deconvolution of the radiative and non-radiative rates enables the correlation of the reduction of the Raman intensity and concomitant increase in the fluorescence yield with the reduction of the non-radiative rate. This confirms that the reduction of the non-radiative rate is the dominant process introduced by the vibrational confinement originating from systematic substitution of higher order acene units into the polymer backbone.     

Space-charge-limited currents for organic solar cells optimisation

Basic suppositions and microphysical origin of the occurrence of the space-charge-limited currents (SCLC) are presented in general and for the temperature-modulated space-charge-limited currents (TM-SCLC) in particular. The criteria are given for the spectroscopical method TM-SCLC to be used for localized electron states elucidation in organic semiconducting materials for organic solar cells optimization and modelling. The “visibility “of the localized states by SCLC method, i.e. the power of the SCLC method to distinguish the localized states, is tested by the modelling, varying the temperature, energy position of localized states and their concentration. Generally, it was determined that the SCLC measurements results are more reliable with the increased energy of the states, with their increased concentration and with decreased temperature. The correlation (or its absence) between the measured current and activation energy on applied voltage, expressed by the dependence of preexponential factor of conductivity on activation energy (Meyer–Neldel rule), gives the possibility to determine the energy range where the reconstruction of density of localized states function is reliable.     

无氢类金刚石碳膜的研究进展

介绍了无氢类金刚石碳膜的制备方法 ,它们的机械、光学、电学性能 ,将无氢与含氢的类金刚石碳膜进行了简单比较 ,总结及探讨了它们的应用