Preparation and characterization of organotransition metal Langmuir-Blodgett films

A novel organotransition metal complex has been synthesized specifically for use with the Langmuir-Blodgett deposition technique. Characterization data for ruthenium (η⁵-cyclopentadienyl)-(bistriphenylphosphine)-4-cyano-4″-n-pentyl-p- terphenyl hexafluorophosphate (RuCTP) are presented, confirming that monolayer and multilayer structures have been successfully prepared.

Complexing of the ruthenium (η⁵-cyclopentadienyl)-(bistriphenylphosphine) group to a liquid crystal molecule greatly enhances the electron withdrawing nature of the resulting molecule and, furthermore, induces multilayer formation. Optical second harmonic generation studies have enabled an estimate of the molecular hyperpolarizability to be made. The value of 40×10^-50 C³ m³ J^-2 is significantly larger than those possessed by many inorganic materials. It has been shown that it is possible to incorporate an average of 1.7 molecules of 4-cyano-4″-n-pentyl-p- terphenyl per molecule of the ruthenium complex into the spaces between the terphenyl chains of the floating RuCTP molecules, resulting in an increased molecular packing density and a corresponding increase of 50% in the second harmonic signal strength.     

Stability and characterization of phospholipid Langmuir-Blodgett films

The regularity of the bilayer structure was compared between dipalmitoylphosphatidic acid (DPPA) Langmuir-Blodgett (LB) films and “oriented multilayers” of DPPA, using X-ray diffraction and electron spectroscopy for chemical analysis (ESCA). The angular variation of the (001) Bragg spot due to the irregularity of the lamellar repeat was remarkable in the system of oriented multilayers. In contrast, the spot of DPPA LB films exhibited only a slight angular variation, suggesting a regular structure of this film. The take-off angle dependence of the phosphorus:carbon ratio obtained by ESCA indicates that the regular layered structure in DPPA LB film is maintained after 49 layers are deposited.     

利用LB技术制备发红光聚苯乙烯超薄膜

利用Langmuir-Blodgett(LB)技术,以二次水为亚相,在亚相表面直接铺展掺杂有稀土配合物Eu(TTA)3phen的苯乙烯分子,然后在一定表面压下进行现场聚合,制得了发红光的聚苯乙烯超薄膜,并用红外光谱、紫外-可见光谱、透射电子显微镜、荧光显微镜、光谱型椭圆偏振仪等对薄膜进行了表征。     

Polar Langmuir-Blodgett films

An optical and electro-optical technique is described for measuring the orientational order parameters $\text{P}\text{(}\text{cos}{}^{\mathrm{n}}\text{θ)}$ of Langmuir-Blodgett films (where θ is the angle between the long molecular axis and the normal to the film plane and $\text{P}$_n are the Legendre polynomials for n = 1, 2, 3, 4). Using these data the orientational distribution function $\text{F}$ (θ) was constructed.Polar multilayers $\text{(}\text{cos}\text{θ}\text{,}\text{cos}{}^3\text{θ}\text{≠ 0)}$ of the X and Z types were obtained from amphiphilic azony compounds. These layers were shown to have a macroscopic electrical polarization P = 10^-6 C cm^-2 and, as a result, they exhibit pyroelectric and piezoelectric properties as well as the linear electro-optical (Stark) effect.     

Preparation and characterization of diamond films

Diamond films were deposited by magnetron sputtering of vitreous carbon disc and also by plasma CVD technique using C₂H₂ + H₂ or CO₂ + H₂ gas mixtures. The films were characterized by measuring the electrical, optical and microstructural properties. FTIR and Raman studies were carried out to study the effect ofsp ² andsp ³ bonds present in the films. The films had a high mechanical stress which was determined from the broadening of the optical absorption tail in the films.     

SiCN薄膜的制备及其性能研究

利用射频溅射法在Si衬底上制备了SiCN薄膜，并利用X射线衍射（XRD）、红外吸收谱（FTIR）和X射线光电子谱（XPS）对薄膜的结构、成份及化学键合状态进行了分析。结果表明，室温制备的SiCN薄膜为非晶状态，并形成了Si-C、Si-N和C－N键；而在高温下（衬底温度为800℃），薄膜中含有SiCN的晶体成分。此外，还利用原子力显微镜（AFM）对薄膜的表面形貌进行了研究，并进一步研究了样品的场发射性能。在场强为24V／μm时，最大发射电流可达3.3mA/cm^2。     

Phospholipid-based potassium-selective Langmuir-Blodgett films

The preparation and properties of mixed Langmuir-Blodgett films of the phospholipid L--phosphatidic acid dipalmitoyl and the ionophore valinomycin are described. IR spectroscopy shows clear evidence for the formation of the valinomycin-potassium complex when these layers are immersed in KCl solutions. However, and in contrast to previous studies with fatty acid-valinomycin mixtures, dissociation of the potassium complex is also observed.     

Preparation and characterization of calix[6]arene Langmuir-Blodgett thin film

Calix[6]arene monolayer/multilayer was prepared on a glass substrate and the behavior of monolayer properties investigated at the air-water interface by taking Langmuir isotherm graph. UV-visible, wettability measurements, atomic force microscopy and quartz crystal microbalance measurements were used to monitor the deposition quality of this Langmuir-Blodgett film. Our results showed that a uniform and high quality film with a transfer ratio of approximately 0.99 occurred using the calix[6]arene material at a deposition pressure of 21 mN/m. The surface free energy was determined to be 25.86 mN/m based on contact angle measurements.     

Preparation and characterization of ultra-thin sol-gel films

The formation and characterization of nanometer thick sol-gel films are reported. The films were prepared by spin-coating of a diluted solution of a silane precursor on a number of different substrates. The effect of dilution, rotation speed and nature of substrate on the thickness and homogeneity of the films was examined. Characterization of the films was carried out by profilometry, reflectance spectroscopy, atomic force microscopy, adhesion test and electrochemistry. We find that the dilution factor has a pronounced effect on the film thickness. Moreover, the time of dilution, namely, whether dilution was carried out before or after a period of hydrolysis, has a noticeable effect on the thickness as well as on the permeability of embedded species.     

Preparation and characterization of doped polyaniline films

Stable monolayer of the polyaniline doped with camphor sulfonic acid at the air-water interface has been obtained, of which multilayers have been successfully deposited by Langmuir–Blodgett technique onto CaF₂ substrate. The limiting mean molecular area and collapse pressure are found to be 0.294 nm² and 41 mN/m, respectively. The multilayers were characterized by IR and UV-Vis-NIR spectroscopies. X-ray small-angle diffraction data show that the multilayer was periodic layer structure with the layer spacing of 1.60 nm. The comparisons are also made with characterization of the casting film.     

Preparation and characterization of Ni-C composite films

Ni-C composite films were prepared using a codeposition method, their structure and electrical properties were investigated. Depending on experimental conditions, two typical structures are found for as-deposited Ni-C films: i) amorphous Ni-C alloy film; ii) granular film with Ni₃C granules and inter-granule amorphous carbon. The amorphous Ni-C films show ohmic conduction behaviour with very high resistivity. On the other hand, granular films with high carbon content show semiconductive characteristics. The electrical property and conduction behaviour are correlated with the film structure. Besides, the crystallization behaviour of the amorphous Ni-C film was also studied.     

Langmuir-Blodgett films from dioctadecylamine picrate

Langmuir-Blodgett (LB) films prepared from picrate of dioctadecylamine(PDODA) and dioctadecylamine (DODA) were studied for the high picrate dipole moment, potentially effective in pyroelectricity. Stable condensed monolayers were obtained on pure water at pH from 5 to 8. About 90% of the PDODA in the films was hydrolysed to DODA. Moderate repulsion between ionized polar heads in the films promoted the desirable X- or Z-type deposition on solid supports, but it prevented a successive deposition of more than five monolayers. At pH below 5 the content of CdCl₂ or picric acid in the subphase decreased the PDODA hydrolysis. Strong repulsion under these conditions caused an expansion of the films and prevented the deposition of more than a single monolayer.     

Langmuir-Blodgett films as chemical sensors

This review covers the fundamental scheme of chemical sensors, fields of major interest in chemical sensors with Langmuir-Blodgett (LB) films, and new and future trends in LB sensor studies. The topics discussed are the relation between sensor characteristics and LB film structure, the biomimetic approach to sensor developments, proposals for transducer improvements, and the possibility of fabricating molecular filters by LB techniques.     

Characterization of copper phthalocyanine Langmuir-Blodgett films

Asymetrically substituted copper phthalocyanine (as-CuPc) Langmuir-Blodgett (LB) films are prepared on metal-coated quartz substrates and the electronic behaviour of sandwich structures of metal/CuPc LB film/metal are studied under normal laboratory ambients. The results show that CuPc films are very stable and reproducible. D.c. measurements produce ohmicI(V) characteristics while the a.c. conductance shows a power-law dependence on the frequency.     

Optical applications of IR-absorbing Langmuir-Blodgett films

Langmuir-Blodgett (LB) films have been produced using a novel near-IR- absorbing dye based on 1,4-naphthoquinone. Wavelength compatibility with semiconductor diode lasers makes it particularly suitable for optical storage applications. Ablative data marks have been recorded using 830 nm light with a pulse energy of 3.6 nJ. The sensitivity is dependent on heat flow within the film and substrate, and can be increased using LB film buffer layers.     

Preparation and characterization of MoC x thin films

Stoichiometric MoC has been calculated to have aT _c of 16 K. To check this prediction, thin films of MoC _x were prepared by sputtering both reactively with CH₄ and using a composite Mo-C target. The preparation conditions were varied over wide ranges of composition, substrate temperature, Ar pressure, and bias voltage. The single-phase B1 structure is formed for substrate temperatures between –100 and 1100°C withT _c values up to 12 K. TheT _c rises with increasing lattice parametera ₀. While films down to about 38 at % C were made, it was not possible to prepare samples with more than about 41 at % C in the B1 phase by this nonequilibrium technique. A linear extrapolation of theT _c versusa ₀ plot yields aT _c value of about 26 K and ana ₀ value of about 0.434 nm for stoichiometric composition. The temperature-dependent specific resistivity is discussed.     

Photopatterning of heterostructured polymer Langmuir-Blodgett films

Heterostructured polymer Langmuir-Blodgett (LB) film prepared by using poly(N-dodecylacrylamide-co-t-butyl 4-vinylphenyl carbonate) (p(DDA-tBVPC53)) and poly(N-neopentyl methacrylamide-co-9-anthrylmethyl methacrylate) (p(nPMA-AMMA10)) polymer LB films which can act as photogenerator layers were investigated. Patterns with a resolution of 0.75 μm were obtained on heterostructured polymer LB films composed of 4 layers of p(nPMA-AMMA10) LB film (top layers) and 40 layers of p(DDA-tBVPC53) LB film (under layers) on a silicon wafer by deep UV irradiation followed by development with 1% tetramethylammonium hydroxide aqueous solution. The sensitivity of the heterostructured polymer LB films was improved without loss of the resolution compared with p(DDA-tBVPC53) LB film. The etch resistance of the heterostructured polymer LB films was sufficiently good to allow patterning of a copper film suitable for photomask fabrication.     

Preparation and characterization of oxidized silver thin films

Silver reacts readily with atomic oxygen, which is present in oxygen plasmas and in low earth orbit. To study the oxidation process, silver films were deposited by r.f. sputtering or by thermal evaporation, then exposed to an oxygen plasma from an electron cyclotron resonance (ECR) source. In-situ spectroscopic ellipsometry (SE) was used to monitor deposition and oxidation, and determine final thicknesses and optical constants. SE indicated that oxidation began at the surface of the silver and proceeded downward, with a rough interface which increased steadily in thickness. Oxide films were nearly transparent over the visible spectrum, where the refractive index was above 2, and were strongly absorbing below 400 nm. Completely oxidized films were twice as thick as the original silver films. They appeared smooth to the eye, and were relatively stable in ambient air. Films that were not oxidized all the way through were much less stable in air, changing interference color and appearing rough within a few days. Oxide films deposited by reactive sputtering of silver in an O₂ background had higher refractive index ( > 2.5) than the ECR oxidized silver films. They were also relatively stable in air, unless deposited onto silver, in which case the samples changed color and appeared rough within a few days, similar to the partially oxidized silver films.     

外延生长碳化硅-石墨烯薄膜的制备及表征研究

石墨烯作为一种碳原子所组成的二维蜂窝状结构晶体,具有诸多优异的特性,从而倍受全世界科学工作者的关注。在碳化硅衬底上外延生长石墨烯是实现石墨烯在微电子领域中应用的最有效途径之一。利用感应加热的高温CVD设备,先在4H-Si C衬底上外延生长一层2~10μm厚的碳化硅,然后直接再在外延碳化硅上原位外延生长石墨烯。实现外延碳化硅-石墨烯的连续生长,从而减少氢气刻蚀带来的晶格缺陷和表面硅富集严重削减现象,并使低成本制备碳化硅上的石墨烯成为可能。通过拉曼光谱、扫描电子显微镜及X射线光电子能谱等表征,验证了该方法生长的石墨烯具有较好的晶体质量。