Electron microscopic phase analysis of BN-thin films

A series of BN films was deposited by means of r.f. magnetron sputtering of a h-BN target onto Si(1OO) surfaces. Hereby, the substrate bias voltage was varied. Special interest is focussed to the influence of the deposition parameters on the orientation of the growing hexagonal BN film with respect to the substrate. For structural investigation, cross section samples were prepared. In addition to HRTEM and diffraction investigations, especially electron energy loss spectroscopy (EELS) was applied successfully for phase identification. For negative bias voltages of U _B =–300 V and U _B =–350V, we found a phase system consisting of a first-grown 25 nm thick layer of hexagonal structure with the c axis parallel to the substrate surface followed by the cubic phase.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Electron Probe Microanalysis of HfO2 Thin Films on Conductive and Insulating Substrates

Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as low-voltage and/or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO₂ films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed. For comparison, Al₂O₃, Ta₂O₅ and TiO₂ films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized by atomic layer deposition method.     

Heterometallic lead-titanium oxyalkoxide precursors to lead titanate thin films

Two lead titanium oxyalkoxides with composition Pb₂Ti₄O₂(O₂CCH₃)₂(OC₂H₅)₁₄ and Pb₂Ti₂O₂(O₂CCH₃)₂(OCH(CH₃)₂)₈ have been isolated and characterised by elemental analysis, IR, ²⁰⁷Pb NMR and molecular weight measurements. X-ray structural analysis of the 1:2 complex confirmed the presence of two Pb₂Ti₂O units which are linked by a common Pb···Pb edge and are held together by alkoxide and acetate bridges. The acetate groups have migrated from the Pb to the Ti centres during the reaction. Hydrolysis of the 1:1 Pb/Ti complex produced clear gels providing the H₂O/complex ratio was less than 4. Heat treatment of the gel results in loss of residual organics below 400°C. The XRD pattern indicates the presence of the pyrochlore and perovskite phases after heating at 500°C but the sample is poorly crystalline. Complete conversion to the perovskite phase of lead titanate occurs on heating to 600°C for 1 hour. Thin films of lead titanate were deposited by dip-coating a solution of this complex in isopropanol. Analyses of the films, carried out using electron microprobe, Scanning Auger Spectroscopy and Rutherford Backscattering, indicated that they were of excellent quality, crystalline after heating at 600°C and with relatively sharp substrate-coating interface.     

Linked crystallites in the conducting topmost layer of polymer bilayer films controlled by temperature: from micro- to nanocrystallites.

Temperature has great impact on the structure and size of the linked crystallites of the conducting topmost layer formed at the surface of a polycarbonate film via the reaction BEDT-TTF+IBr [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene]. We show that fine temperature control permits formation of a semiconducting topmost layer of alpha'-(BEDT-TTF)(2)(I(x)Br(1-x))(3) crystallites with either micro- or nanometre size, a result that opens a route to miniaturized conducting plastic materials.     

pH值和钙离子对尖吻蝮蛇抗血小板凝集素二级结构的影响

尖吻蝮蛇毒中抗血小板凝集素是凝血因子IX/凝血因子X结合蛋白，它具有抗凝血和抑制血小板凝集双重活性。用红外光谱、拉曼光谱和CD谱研究了抗血小板凝集素的二级结构以及pH值和钙离子对其二级结构的影响。用CD谱测得，在水溶液中，抗血小板凝集素的主要骨架构象为β-折叠(26.3%)和α-螺旋(19.6%)结构。拉曼光谱显示，在粉末状态，其α-螺旋含量显著降低。CD谱还表明，抗血小板凝集素在pH值3.0～11.0范围内保持稳定的天然结构，钙离子诱导的抗血小板凝集素结构变化是可逆的，钙离子在稳定抗血小板凝集素的天然结构中起重要作用。     

Selective Formation of Spinel Iron Oxide in Thin Films by Complexing Agent-Assisted Sol-Gel Processing

The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, α-Fe₂O₃ with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one mole of iron nitrate and the calcination temperatures were below 400°C, ψ-Fe₂O₃ with spinel structure appeared as the main phase and, when less than five moles of the diols were used, α-Fe₂O₃ appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in thin films. Thus, a transparent magnetic film composed of γ-Fe₂O₃ could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz and calcining the gel film at 350°C.     

溶胶-凝胶法制备高取向Bi4Ti3O12/SrTiO3(100)薄膜

Bi4Ti3O12具有良好的铁电、电光等性能山、特别是Bi4Ti3O12薄膜很适合作永久性存储材料，也可用于电光器件问．在微电子学、光电子学、集成光学、集成铁电学等领域均有广泛开发和应用前景，国外已用溅射法、激光沉积法制备出c轴取向Bi。Ti3Ol。薄膜【’，＼山东大学用MOCVD法制     

Circular Dichroism Study of the Inclusion-Dissociation Behavior of Complexes between a Molecular Nanotube and Azobenzene Substituted Linear Polymers

We have investigated the inclusion properties of molecular nanotubes composed ofcrosslinked -cyclodextrin. Induced circular dichroism was used to probe theformation and dissociation of complexes between the nanotubes and azobenzenemodified linear polymers. The polymer was poly(ethylene glycol) (PEG), either withor without a hydrophobic alkyl chain.It was found that the inclusion complex betweenthe nanotubes and polymers formed at room temperature, and that the polymers dissociated from the nanotubes with increasing temperature. Further, the polymer with hydrophobic alkyl chain was bound inside the nanotube more strongly and dissociated more abruptly with increasing temperature than its hydrophilic counterpart as expected theoretically.     

Voltammetric, chronocoulometric and spectroelectrochemical studies of electropolymerized films based on Co(III/II)- and Zn(II)-4,9,16,23-tetraaminophthalocyanine: effect of high pH

Electropolymerized thin films of Co(III/II)- and Zn(II)-4,9,16,23-tetraaminophthalocyanine, immersed in solutions of relatively high pH, have been studied electro- and spectroelectrochemically. Cyclic voltammetry and chronocoulometry were used to characterize films deposited on glassy carbon electrodes. Spectroelectrochemistry and ellipsometry measurements were performed on indium tin oxide (ITO) surfaces coated with the zinc and cobalt complexes and correlated to the electrochemical information collected using glassy carbon electrodes. Studies at high pH are motivated by the efficient increase in luminol chemiluminescence at high OH⁻ concentration, and by potential application in luminescence sensors. Although the films are not removed, some structural changes occur when they are exposed to solutions of high pH. In addition, an estimation of the number of monolayers has also been calculated. The atomic diameters of cobalt and zinc are very close in value, but the estimated number of monolayers, based on cyclic voltammetric data, for a given number of electropolymerization cycles is approximately four-fold higher in the zinc-based film. This would correspond to three-fold thicker films when zinc is the central metal ion. Ellipsometry measurements have been correlated with cyclic voltammetric data to confirm that film thickness varies among the different complexes, even though the conditions of electropolymerization are the same.     

Chiral amplification in macromolecular helicity assisted by noncovalent interaction with achiral amines and memory of the helical chirality

Poly[(4-carboxyphenyl)acetylene] (poly-1) exhibits an intense induced circular dichroism (ICD) in the UV-visible region upon complexation with excess (R)-1-(1-naphthyl)ethylamine ((R)-2), owing to the formation of a predominantly single-handed helical conformation of the polymer backbone. In the presence of a small amount of (R)-2, poly-1 showed a very weak ICD due to the lack of a single-handed helical conformation. However, we have found that the co-addition of the excess bulky, achiral 1-naphthylmethylamine (5) with a small amount of (R)-2 caused a dramatic increase in the ICD magnitude, comparable to the full ICD induced by excess (R)-2. This indicates that an almost single-handed helix can be induced on poly-1 upon complexation with a small amount of (R)-2 assisted by achiral 5. Furthermore, the induced single-handed helical poly-1 could be successfully memorized by the replacement of (R)-2 and 5 with achiral 2-aminoethanol or n-butylamine.