Amorphous films in the system ZrO₂-Al₂O₃ were prepared by rf-sputtering and their density, refractive index and thermal expansion were measured. A maximum and a minimum were observed in the density and refractive index at about 15 mol% ZrO₂ and 50 mol%ZrO₂, respectively. In the thermal expansion coefficient, a minimum was observe d at about 15 mol% ZrO₂. The coordination states of cations in these amorphous films were determined by the chemical shift of aluminum K_a X-ray emission spectra for aluminum ions and by the change of molar refractivity of zirconium dioxide for zirconium ions. The mean coordination number of aluminum ions changed from five to a slightly lower value. On the other hand, the coordination number of zirconium ions in the amorphous films below 15 mol% ZrO₂ content was below six, but it became almost six, independent of ZrO₂ content, in the region of more than 20 mol% ZrO₂.

View full abstract

Multilayers of Mo/AI were synthesized by an rf magnetron sputtering system with a rotating table and only one cathode. The modulation wavelengths ranged from 600Å down to 17Å. The structural properties have been studied by using X-ray diffraction. Films were composed of layers of bcc Mo and fcc Al oriented along the [110] and [111]directions, respectively. To understand the X-ray data, model calculations based on a simple scattering theory were performed. A trapezoidal wave model was found to be in good qualitative agreement with the measurements. The in-plane resistivity was measured as a function of wavelengths and temperature in the range 4-280 K by a four electrode method. The resistivity did not saturate even at very small wavelength and depended linearly on theinverse wavelength for wavelengths larger than 60 Å. The temperature coefficient of resistivity (TCR) changed sign at about 60Å in this system.

View full abstract

Amorphous LaNi₅, films were ptepared by a sputtering method. Hydrogenation characteristics of the films were investigated and the results were compared with those of the evaporated films.
The density of the sputtered LaNi₅ film was about 6 g/cm³, which was larger than that of the evaporated film. Thermal conductivities of the films were larger than those of a bulk sample,

View full abstract

The structure of Mn-Sb multilayerd films has beep investigated by transmission electron microscopy. Well oriented Sb buffer layers with thickness of 300Å are formed when they are deposited on non-crystalline triacetylcellulose films. When a Mn layer is deposited on the Sb buffer layer, an intermetallic compound MnSb is formed epitaxially on the Sb layer. The epitaxial growth was confirmed by electron diffraction patterns (Figs.3 and 4), X-ray diffraction, pattern (Fig.5) and bright field images (Figs.6 and 7).

View full abstract

Five kinds of amorphous tin oxide films were prepared by reactive evaporation under various conditions. The composition and thermal behavior of the films were studied, by TG, DSC, X-ray diffraction and ¹¹⁹Sn Mssbauer measurements. Depending on the deposition condition, the films had some composition in the range of SnO_1.3-SnO_1.5. The microstructure of the films was porous, this porosity decreased at higher deposition temperatures. When films were heated in air, they were perfectly oxidized at about 200°C, and then crystallized to ruffle-type SnO₂ at about 370°C. In the N₂ gas, films were crystallized to two phases of α-SnO and rutile-type SnO₂ at about 400°C.

View full abstract

A superlattice consisting of metallic iron and its oxide could be formed by repeating vacuum depositions of iron at 10^-5 Pa and subsequent surface oxidations at 10^-1 Pa. Bragg peaks due to the metal-oxide stacking periodicity were observed which indicated that the thickness of the oxide layer was uniform. The magnetization curve and the Mssbauer spectra showed that the thickness of the metal surface oxidized at 10^-1 Pa was almost constant at O.7 nm, irrespective of the thickness of the deposited metal layer, and that the oxide layer consisted of ultrathin layer of Fe₃O₄. When the deposited metallic layer was thicker than 2 nm, a ferromagnetic magnetization curve was observed from the continuous film. However, a superparamagnetic behavior suggesting formation of island-like fine particles was observed when the thickness was 1 nm.

View full abstract

Boron ions were implanted in Ti films with a high dose of 7.14×10¹⁷ and 2.30×10¹⁸ ions/cm². Depth profiles of the concentration of boron ions were measured by a second ary ion mass spectroscopy. Even at extremely high dose implantation of boron ions, the mean project range Rp coincided well with theoretical values predicted from LSS theory. At the dose of 2.30×10¹⁸ ions/cm² the maximum boron ion concentration was higher than that of TiB₃, synthesized by a solid reaction. The formation of very fine-grained TiB₂ was confirmed by X-ray diffraction, and the reaction process is discussed. The temperature coefficient of electrical conductivity of B⁺ implanted 170 nm thick films was as low as 0.3 ppm/K in the temperature range from 4.2 to 350 K, so it was regarded as almos t constant. This fact may be correlated with the microstructure of the implanted films consisting of fine-grained TiB₂ crystallites.

View full abstract

We fabricated a sample having the structure of electrode-Cr doped Y₂O₃ thin film-electrode by the RF sputtering technique, and applied the photocurrent method to the sample. The photocurrent observed at wavelengths shorter than 450 nm is attributed to the charge transfer from the valence band to Cr⁵⁺, and a peak of the photocurrent at 370 nm is assigned to the electron transfer from the excited states of Cr⁵⁺ to the conduction band. By means of double source photocurrent measurements, the energy level of the oxygen vacancy states is estimated to be located at ca. 2eV below the conduction band.

View full abstract

The ionized cluster beam (ICB) method is one of the novel ion-assisted techniques for film formation, which enables formation and transportation of low energy and equivalently high current ion beams. The clusters, large size macro-aggregates of 100-2000 atoms, are formed by condensing pure vapor of normally solid materials in an adiabatic expansion process. The ICB causes special film formation mechanism due to the peculiar properties of clusters in addition to the effects of kinetic energy and electric charge of ions. This technique allows unique film formations, such as low temperature epitaxy, hetero-epitaxy with large misfit combinations, formation of ultra-thin films and very smooth film surfaces, and enables control on crystal structure, chemical composition, and miscellaneous electrical properties of the film. This paper includes room temperature epitaxy of thermally stable Al on Si substrate, surface morphology control of epitaxial CaF₂ films, formation of CdTe-PbTe multilayered structure, and crystal structure control of TiO₂ films by reactive ICB method. ICB method is also effective for organic film formation with high crystallinity and improved electrical characteristics. Some results for Cu-phthalocyanine and polyethylene thin films are given.

View full abstract

Film growth using ion-based techniques has become an useful method of preparing films at lower substrate temperatures. In various ion-based techniques, it is characteristics of the ionized cluster beam (ICB) technique that macro-aggregates of atoms (clusters)formed from deposited material vapor are utilized instead of atomic or molecular state particles, and that the structural properties of films are artificially controlled by adjusting the acceleration voltage and the content of ions. The roles of ions in film formation are to enhance the chemical activity of vaporized materials and to promote film growth along a particular crystal axis at lower substrate temperatures compared with conventional vacuum evaporation system, but the elementary mechanisms of nucleus and film growth at the initial stages have remained obscure. Therefore, an attempt to investigate the effects of cluster ions on film growth was made for Bi and Te films, which were deposited simultaneously on a glass (insulating) and an Al coated glass (conducting) substrate. The major results obtained ar e as follows: (1) the presence of ions, even though the content of ions is only -a few per cent in the total flux, brings about a marked change in the condensation process of the deposited materials. (2) The structural parameters of nuclei at the initial stage can be modified by adjuisting the total ionic charge and their kinetic energies. (3) The effect of ions on film growth along a particular crystal axis is qualitatively explained by using a valence bond orbital model.

View full abstract

Electrochromic β-ZrClN films have been prepared by RF plasma CVD from the system of ZrCl₄-N₂-NH₃. No films were formed from the system of ZrCl₄-N₂, and zirconium nitride films with zirconium deficit were formed from the system of ZrCl₄-NH₃. When the plasma of ZrCl₄-N₂-NH₃ was used at the mixing ratio NH₃/N₂=1/5, yellow α-ZrClN films were deposited at the temperatures ranging from 400 to 600°C. The yellow film was converted into β-ZrClN film of pale yellow green by the heat treatment at 630°C in flowing nitrogen. The resulting film has good transparency and the scanning electron micrograph showed that the fine platelets of β-ZrClN were deposited with the planes perpendicular to the substrate. The α-ZrClN film was also treated in NH₃ at 630°C, which resulted in the removal of chlorine from the film, and amorphous Zr-N film was formed. The amorphous as well as β-ZrClN films exhibited electrochromic behavior.

View full abstract

Nucleation of photo-CVD amorphous silicon (a-Si) from disilane on Si0₂ substrate was studied by using an Xe pulse tube as the light source. Detection of small Si nuclei was done rthrough chemical pre-amplification to colloidal silver, followed by examination with TEM. Clearly definite saturation was found in the relationships between Si necleus density and total number of light pulses, suggestive of island type growth and the contribution of surface diffusion of active radical species. The initial nucleation rate was found to increase with substrate temperature at least between 150 and 250°C, which may reflect the characteristic of the photo-CVD nucleation. When the pulse interruption period was varied from 20 ms to the order of seconds for a total of 2000 pulses, the Si nucleus density remained constant till a certain critical period which depended on substrate temperature and then decreased rapidly. This unique phenomenon was discussed from a kinetic point of view.

View full abstract

The films of vanadium nitride were deposited on silica glass substrates from the gas mixture of VCl₄-N₂-H₂-Ar under the atmospheric pressure. The deposition rate, the phase, and microstructure of deposits were investigated as a function of the experimental parameters such as deposition temperature, total gas flow rate, and input gas composition. The range of experimental conditions were as follows: deposition temperature: 700-1100°C, total flow rate: 1-4 l/min, Pvcl4: 0.2-2.O×10^-2 atm, P_N2 and P_H2: 0.05-0.4 atm. The nitride films were formed above 900°C. The films consisted mostly of δ-VN, and β-V₂N was codeposited when P_vcl4 was high. A linear relationship was observed between the deposition rate and 1/T below 1000°C, and the apparent activation energy calculated from its slope was about 180 kJ/mol. This result suggests the deposition is controlled by surface reactions. From the dependence of the deposition rate on the gas composition, the deposition mechanism of vanadium nitride films has been discussed.

View full abstract

The thermodynamic calculations and the experimental results for the chemical vapor deposition of the Si-Ti-C-H-Cl system using SiCl₄, TiCl₄, CCl₄ and H₂ as source gases were compared. The thermodynamic calculations well explained the experimental results for the formation of such phases as the SiC+TiC, the SiC+TiC+C and the TiC+Ti₃SiO₂. The main gas species in equilibrium are (H₂), (HCl), (SiCl₂) and (TiCl₃). The equilibrium (H₂) and (HCl) partial pressures are almost independent of temperature. The equilibrium (SiCl₂) partial pressure increases with increasing temperature, and the equilibrium (TiCl₃)partial pressure decreases with increasing temperature. The theoretical deposition efficiency of ‹SiC› decreases with increasing temperature, and that of ‹TiC› increases with increasing temperature. The calculated compositions of SiC/(SiC+TiC) in the SiC+TiC phase were almost in agreement with the experimental values. The calculated compositions of SiC/(SiC+TiC) decrease with increasing temperature. However the experimentally obtained compositions increased with increasing temperature, which may be caused by the kinetic restriction for the formation of the ‹SiC› at lower deposition temperatures.

View full abstract

The TiO₂ films doped with various amounts of Sb₂O₃ have been prepared by the sot-gel method and their photoelectrochemical properties have been investigated. The ESCA analysis revealed that antimony atoms in the Ti0₂ (anatase), heated at 600°C for 20 min, were present in the state of Sb³⁺, not of Sb⁵⁺. From the concentration dependences of donor density and resistance of the Sb₂O₃-doped TiO₂ films, the solubility limit of Sb₂O₃ in the TiO₂ (anatase) was estimated to be around 1 mol%. The photocurrent of the TiO₂ films increased up to about 26 mA.cm^-2 by the addition of 0.5 mol% Sb₂0₃, but decreased drastically with further increase in the doping concentration, accompanied by the decrease in the slope of onset photocurrent and the shift of onset potential to the positive side. These phenomena can be explained by the formation of impurity level of SY+ in the band gap of TiO2 which acts as the recombination center. It was further found that Sb₂0₃ in TiO₂ undertook a dissolution reaction by the photogenerated holes under illumination.

View full abstract

Zr02-Si02 coating films of high Zr0₂ contents (over 50 mol%), including pure Zr0₂ films have been prepared from zirconium n-butoxide and silicon ethoxide by the sol-gel method. These alkoxides were hydrolyzed by the moisture in air and the coating was carried out in a humidity-controlled glove box, because zirconium n-butoxide was highly hydrolyzable. It was found that the properties of the films obtained, such as optical transmission and surface roughness, were primarily governed by the relative hum idity in the coating process: The optical transmission decreased and the surface roughness increased as the humidity was increased. The decrease of transmission, as well as the increase in surface roughness, was due to the deposition of zirconium oxide or its hydrates in the films. The transparent films, however, were obtained below 20% of relative humidity. The refractive index of the Zr0₂-Si0₂ films decreased linearly with an increase in the SiO₂ content, going down to 1.48 at 100 mol% Si0₂, which coincides closely with th at of fused silica. This finding indicates that the films obtained are very homogeneous and there is little difference between the compositions of the films produced and the nominal compositions in the starting solutions. The films of high Zr0₂ contents were very durable to alkaline solutions, showing their potential possibility as alkaline-resistant coatings.

View full abstract

Transparent amorphous films in the system Li₂O-SiO₂ were prepared from silicon tetraethoxide and lithium alkoxide by the sot-gel method. The surface roughness was dependent on the species of solvent used in the preparation and the composition of the films. The surface roughness was smaller for the films prepared using methanol as a solvent than for those using ethanol. The electrical conductivity for the films with relatively small amounts of lithium was found to increase with an increase in the heat-treatment temperatures below the crystallization temperature Talthough a small hump was observed. The observation of such a hump in conductivity suggests that the films containing some residual organics would have a favorable structure for the conduction of Li⁺ ions. The conductivity value at 500 K of 10^-3 S.cm^-1, which was as high as that of the corresponding rapidly quenched Li₂0-SiO₂ glasses, was obtained when the heat-treatment was carried out slightly below T_e. The activation energy for conduction and the preexponential factor were also found to approach those values of the rapidly quenched glasses with increasing the heattreatment temperatures below T_e. The conductivity of the films with large amounts of lithium oxide was found to be much smaller than that of the corresponding rapidly quenched glass at any heat-treatment temperatures. this result is considered to be caused mainly by the formation of Li₂CO₃ in these films.

View full abstract

Highly dispersed nickel and cobalt catalysts supported on active carbon or alumina have been prepared by a thermal decomposition of the precursor of a cellulose-hydrous metal oxide gel membrane or that of an alumina-metal nitrate gel membrane. The precursor of a gel membrane was obtained from a sol-gel process using ultra fine alumina sol derived from aluminum chloride or a finely porous cellulose gel membrane. The size of a catalyst particle is controlled by the dimensions of the gel network of a homogeneous precursor gel. The reaction properties of such a catalyst have been investigated in the hydrogenation of 1, 3- or 1, 5-cyclooctadienes. The selectivity for monoene and activity tends to increase with decreasing size of the catalyst particle (5-20 nm). The selectivity for monoene by the catalyst is higher than or close to that of the impregnated catalyst. However, the activity is generally lower than that of Raney catalyst. This may be attributable to the tendency of metal particle to be coated with support material. This preparation should produce well-dispersed metal particles supported on active carbon or alumina in one step. It can this simplify the fixation process of metal particles on supports which is usually employed in the preparation of the ultra fine catalyst particles.

View full abstract

The characteristics of the titanium dioxide (Ti02) thin, transparent electrodes prepared with spray-pyrolysis were studied. Titanium-oxi-acetylacetonate_ was employed as, starting material suspended in ethanol. The thickness of TiO2 films thus prepared was *proportional to the amount of the sprayed solution, and was found to be ca.200 nm when 100 cm3. of solution was sprayed. X-ray diffraction studies and SEM observations showed that the films consist of polycrystalline anatase, and the size of the grains was 20-50 nm. MottSchottky plots showed that the doner density of these electrodes was 1017-1018 cm-3 and the flat band potential was -0.2--O.4 V vs. SCE. The quantum efficiency of the photocurrent was estimated to be 40-60%. These values are comparable well with those of the TiO2 electrode prepared with the other methods, e. q. reactive spattering and heat oxidation of titanium. The spray-pyrolysis method was found to be simple, cheap, but sufficiently feasible for preparing TiO2 thin film photoelectrode.

View full abstract

Effects of potassium dihydrogenpyrophosphate and boric acid for the palladium electrodeposition from the potassium thiocyanatepalladium(II) chloride solution have been studied. The potential for metal deposition in a thiocyanic acid solution containing palladium(II)ion was more positive than that in the absence of palladium(II) ion, with depression of hydrogen evolution. The addition of potassium dihydrogenpyrophosphate to the thiocyanic acid solution containing palladium (II) ion made the potential for the palladium deposition more negative than that in the absence of potassium dihydrogenpyrophosphate. Addition of boric acid made the potential further negative. The potassium dihydrogenpyrophosphate increased the limiting current density for H2 evolution and controlled the pH variation of the. electrode surface. The absence of either potassium dihydrogenpyrophosphate or boric acid caused the formation of a crack in electrodeposit for the palladium deposition. At the surface of the palladium deposition gained from the potassium thiocyanatepalladium chloride solution contaning both potassium dihydrogenpyrophosphate and boric acid, cathode current efficiency increased.

View full abstract

When the ferrite-plating method was used, ferrite films could be piled up on various substrates at 50-90°C in aqueous solution. On the basis of our experimental results, the ferriteplating reactions were herein discussed, and some discrepancies among three typical methods: “rotating disc method”, “thin liquid-film method” and “spray-spin-coating method, ” were recognized. According to the relationships among the film deposition rate, the preferential texturing, the concentration of the oxidizing reagents and the electrochemical characteristics on the surface of the ferrite-layer, two types of reaction were postulated. These took place under Fe²⁺-rich and/or oxidation conditions on the surface of the ferritelayer. The formation of ferrite films seemed to be a result of the dissolution-deposition process under the condition of Fe²⁺-rich side.

View full abstract

Composite films of magnesium oxide and metals (Au, Fe and Ti) are prepared by a simultaneous deposition technique. An important features of MgO-Au and MgO-Fe composite films is that metal is grown epitaxially and separately with the size of around 3 nm and 1 nm, respectively. The heat treatment for composite films of MgO-Fe at 500°C for 1 h and 1000°C for a few minutes bring about a grain growth of α-Fe up to 5 nm and a phase transformation of α-Fe to γ-Fe and quenched in to the room temperature, respectively. A strain of γ-Fe particles embedded is analysed through the distortion of the moire fringes. For MgO-Ti composite films, Ti grows as fine crystallites less than 1 nm with the structure of Ti_1-x0 with ordered vacancies. The heat treatment at 1000°C for a few minutes brings about the formation of Mg₂TiO₄ with the spinel structure.

View full abstract

Poly(ethylene terephthalate) (PET) films were treated by H₂O plasma. The wettability of the PET film surface and its adhesivity to Co deposited thin films were investigated. The wettability of PET films was improved by H₂O plasma treatment, and the surface modified PET film adhered strongly to Co deposited thin films. For lower radio frequency (RF) power (25 W) during H₂O plasma treatment, the wettability of PET films was slowly improved with an increase in the treatment time, and the adhesivity to Co deposited thin films was improved remarkably at a shorter treatment time. For Higher RF power (100 W)the wettability of PET film was immediately improved, and the adhesion to Co deposited thin films was improved abruptly with treatment time. PET film showed specific magnetic characterizations.

View full abstract

N2+ ion implantation has been made to the 200 nm thick iron films. The analysis of the X-ray diffraction patterns revealed that at the dose of 4.0×10¹⁶ (N₂/cm²), nearly 35%of cubic iron in the film was transformed to body-centered tetragonal FeN, with orientation of its c-axis perpendicular to the film plane. Saturation magnetization of the implanted film at R. T. increased 2.8%, which can be interpreted by presence of Fe₁₆N₂. The expected value of the saturation magnetization 4 πM₈. of Fe₁₆N₂ was calculated to be 23.5 kG. The nitrogen implantation also induced magnetic anisotropy perpendicular to the film plane.

View full abstract

Polycrystalline (Mn, Zn)Fe₂O₄ films were prepared on silica glass substrate by CVD using three kinds of acetylacetonatocomplexes, Mn(acac)₂, Fe(acac)₃ and Zn(acac)₂.H₂O as starting materials. These complexes were evaporated at a reduced total pressure of 10 Torr and at temperatures of 205°C, 140-150°C and 85°C, respectively and transported with nitrogen carrier gas to the deposition zone. The growth conditions and magnetic properties of the polycrystalline (Mn, Zn)Fe₂O₄ films were as follows. deposition temperature: 500-600°C, oxygen gas flow rate: 10 ml/min, reaction time: 20 min, saturation magnetization: 50 emu/g, coercive force: 80 Oe and Curie temperature: 270°C.

View full abstract

CdSexTe1-x(0<x<1) thin films were deposited on Ti sheets from an acidic solution (pH=1.4) containing 1 mol.dm^-3 CdSO₄ and SeO₂+TeO₂, the total concentration of which was 1 mmol.dm-3. Although the stable structure of CdSe is wurtzite, all the deposited films had zinc blend structure. The lattice constant depended on the SeO₂/TeO₂ ratio in solution.

View full abstract

A novel method for preparing amorphous Silicon films is proposed, in which silane is decomposed oxidatively to afford the precursors responsible for the deposition by a chemical reaction with fluorine at reduced pressure. The proposed technique is quite simple and provides a feasibility of controlling over the chemical structure and the hydrogen content in the films through the external parameters in the gas phase reaction. The films show high photoconductivity comparable to those pre pared by rf-glow discharge of silane.

View full abstract

The thin films of metallocene, such as dichlorobis(cyclopentadienyl)titanium[TiCl₂(cp)₂]were prepared by vacuum depositionion (VD) method and radio frequency ion plating (RFIP) with 13.56 MHz discharge to study the structures and electrical characteristics of the films. The thin film formed by ordinary vacuum deposition was same as the [TiCl₂.(cp)₂] monomer in the structure, and had high electrical resistivity. The thin film formed by ion plating had some of crosslinking structure, but the crystal structure of [TiCl₂(cp)₂] monomer remained in the thin film. [TiCl₂(cp)₂] thin films showed approximately similar IR spectra to that of [TiCl₂(cp)₂] monomer, but each peak was broadened with the increase of rf power. FroFri the analysis of XPS spectra of [TiCl₂(cp)₂] thin film, Ti/C ratio in the thin film farmed. by ion plating was similar to that of [TiCl₂(cp)2] monomer, but the peak of Cl atom decreased with the increase of the rf power. It was found that the electrical resistiity of [TiCl₂(cp)₂] thin film formed by ion plating varied uniformly according to the humidity with the high sensitivity.

View full abstract

Various kinds of metal phthalocyanines (Pc) and their alkoxy derivatives were plasmapolymerized and the effects of metals and alkoxy substituents on the photovoltaic as well as photocatalytic characteristics were investigated. The greenish polymeric films with thickn ess 500-900 nm showed photovoltaic effect with the efficiencies of 10^-6-10^-4%, which increased with decreasing light intensity. The obtained films also showed photocatalytic effect and could reduce methylviologen under visible light. The catalytic activities of plasma-polymerized thin films were as high as those of monomeric phthalocyanine particle.

View full abstract

The effect of the deposition rate on the crystallinity of vacuum-deposited films of phthalocyanine and the formation of ligand-coordinated phthalocyanine films were studied. The crystallinity of phthalocyanine films increased as the deposition rate was lowered even if the substrate was kept at room temperature. The film deposited at the rate less than 100 A/min had especially high crystallinity which was comparable to that of the film deposited on the substrate prepared at 200°C. Using these deposition conditions the formation of ligand-coordinated phthalocyanine film was studied by the co-deposition method. Iron phthalocyanine (FePc) and 1, 2-bis(diphenylphosphino)ethane (DPP) as ligand were evaporated from two sources simultaneously. Coordination of DPP with FePc was confirmed by the measurements of infrared spectra and visible light absorption spectra. The ratio of DPP/FePc was determined as 2/1 by fluorescence X-ray measurement X-Ray diffraction pattern of the FePc-DPP film showed the peak having a d-value of 12.1A. This indicated that the FePc-DPP film had a crystalline form. It was re vealed that the ligand-coordinated phthalocyanine films could be formed by the rate-controlled co-deposition method.

View full abstract

Radical species were separated from O₂, N₂ and Ar plasmas formed by the glow discharge at 20 kHz frequency, and then used as initiation agents for surface modification and thin film formation. The concentration of radicals separated from the plasmas depended on the pressure of the reaction chamber (Table 1) as well as the distance from the plasma generator (Fig.4). When polyethylene sheets were exposed to the radical beams, the surface was modified to be hydrophilic (the surface energy of the modified was ca.60 kN/m) (Table 2). Thin films were deposited by exposing stryrene vapor to the radicals. However the polymer deposition rate was retarded to a quarter compared with that by exposure to plasma. The chemical composition of the polymer was fairly different from that of plasma polymers from styrene but similar to conventionally polymerized polystyrene. This result suggests that a less degraded polymer films, especially with less degradation in the phenyl group, could be formed by the radical beam compared with plasma polymerization.

View full abstract

The electrochemical oxidation of 1-naphthylamine at a basal-plane pyrolytic graphite (or an In-Sn oxide conducting glass) electrode in an acetonitrile solution led to the polymeric film-coating of the electrode surface. The resulting poly(1-naphthylamine) (PNA)film showed a reversible redox response in aqueous solutions containing supporting electrolytes only. The PNA film was also electroactive in an acetonitrile solution. The formal oxidationreduction potentials (E^o') of the PNA film in a O.2 mol.dm^-3 NaClO₄ aqueous solution (pH 1.0) and a 0.2 mol.dm^-3 NaCl0₄ acetonitrile solution were 0.22 and 0.15 V vs. a sodium chloride saturated calomel electrode, respectively. The Eo' vs. pH plot was linear in the range of pH 1 to 6, and the slope was about 57 mV/pH, indicating that protons and electrons take part in the electrode reaction of the PNA film in a 1/1 ratio. The conductivity of the film was 10^-7--10^-6 S.cm^-1 at 300 K. From the analysis of the IR absorption spectrum and the electrochemical behavior of the film, it was found that the electropolymerization of 1-naphthylamine proceeds via the formation of C-NH-C and C=N-C bonds at the 1- and 2-positions and/or the 1- and 4-positions with, respect to the amino group.

View full abstract

A ultrathin membrane with high oxygen permeability was prepared from a crosslinked ternary copolymer [poly-(hydroxystyrene)-poly(dimethylsiloxane)-polysulfone: abbreviated as HS copolymer]. The membrane was produced by spreading the dilute solutions on water surface (abbreviated as SW method). The configuration of the membrane was investigated by comparing with those of a monolayer and a multilayer of HS copolymer. From the surface pressure-area isotherm measurements, it was suggested that a monolayer of HS copolymer on the surface of water has a configuration in which hydrophobic dimethylsiloxane segment is emersed and hydrophilic segment is immersed in water. The monolayers were deposited on a glass substrate or porous polypropylene film by horizontal lifting method lifted from either water side or air side. Measurements of XPS and the water contact angle (θ) for the surface showed that the configuration of the monolayer is retained even in the multilayer. The values of θ of the membrane by SW method was in fair agreement with the values of the multilayer lifted from water side and air side. Oxygen permeability coefficient was measured as 9.2×10^-2 (cm³/10.17 cm².s.atm) and selectivity (O₂/N₂) as 2.02 for above membrane. Similar values were obtained for multilayer composed of more than 6 layers. These results indicate that the ultrathin membrane by SW method has the same orientation as a multilayer. No specific permeable behavior was observed in the membrane though it has the surface oriented structure.

View full abstract

Transport of ions across the membranes was studied by use of porous glass (average pore radius of 20A, corning #7930) modified with [3-(2-aminoethylamino)propyl]trimethoxysilane, Membrane potential was generated in the system with two aqueous solutions of different concentration of KCl, KNO₃, or CH₃COOK separated by the modified membrane. (Fig.4) The membrane potential agree with the Theorell-Meyer-Sievers Theory. The fixed charge density of the modified porous glass membrane increased with the increase of the concentration of silane solution used in the modification reaction, while saturated at higher concentration than 0.01 mol.dm^-3. This means a unit fixed charge occupies the area of 1500A² on the glass surface. This value is too large if compared with the least crosssectional area of one silane molecule. The addition of copper(II) ion in KCl solution decreased the membrane potential. It was presumed that copper(II) ion forms a complex with aminoethylamino groups on the modified porous glass surface, which might lower the fixed charge density of the modified membrane.

View full abstract

A fully microprocessor-controlled film balance and a film lift system were constructed (Fig.3). The speed of the moving barrier, which is driven by a vibration-free pulse motor system coupled with linear ball bearing and threaded screw (2 mm pich) (Fig.1), is changeable from 0.04 mm/s to 8 mm/s. The resolution and the accuracy of the barrier position are 40 μm. Feed-back con trol from a pressure sensor (Wilhelmy plate system using a load cell sensor)enables measurement of pressure-area isotherms by the pressure-equilibration mode (Fig.5). The isotherm of stearic acid obtained by this mode was different from that of the constantspeed mode (Fig.6). The vibration-free film lift, driven by a timing belt-pulse motor system (Fig.2), and the high resolution (0.03 mN/m) of the pressure sensor are effective for preparation of LB films with good quality. All data and conditions are transferred to a personal computer through the RS 232 C communication interface and analyzed by a BASIC program. Changeable control parameters enable measurements under precisely-set conditjons.

View full abstract

We have tried to develop one of the downstreams of Langmuir-Blodgett methods by using the dyer's technics known as “suminagashi” (“nagashi” means “to let flow”). This kind of work was originally investigated scientifically by Torahiko Terada. A drop of Chinese ink (“sumi”) attached xo a glass rod was spread on the surface of aqueous cadmium chloride solution and a thin film was formed after several times of spreading. In the center of the film of ink, a weighed quantity of a solution of arachic acid in benzene was dropped, and the film was transferred to graph paper by blotting. The film was composed of two parts, which were the ink film and a white region where the ink film had been pushed away by the surface pressure of the arachic acid molecules. The area of this white part which was occupied by arachic acid molecules, was measured by counting sections of the grid on the paper. The method was also applicable for stu dying the spreadability of enamel proteins prepared from porcine enamel samples at early stage of development. Perfluoroalkyl polyether transferred on a section paper by the “suminagashi” was found to be detected by ESCA spectrometry.

View full abstract

The preparation of the LB film from the monolayer spread on water surface was attempted by the use of various iron(III) salts. Iron(III) octadecylsuccinate, hydroxide dipalmitate, hydroxide distearate, tripalmitate, and tristearate were synthesized and examined for the film formation. Only iron (III) hydroxide dialkanoates permitted the formation of the LB film up to about 100 layers on a plate of Ferrotype or a glass plate at 25 mN.m^-1. It was found very difficult to built up the other iron salts to be deposited in a complete layer structure. The properties of the LB film obtained from iron(III) hydroxide distearate were characterized by means of ESCA, X-ray diffraction, and IR. The ESCA measurements suggested the presence of iron(III) hydroxide distearate molecules in the LB film. The X-ray diffraction showed that the film structure was composed of the double layer arrangements in which the interlayer distance of iron (III) ions was O.22 nm shorter than that in the powder crystals. The thermal stability was tested by measuring the LB film of 30 layers deposited directly on a ZnSe photoprism. It was found that the film structure remains unchanged at room temperature for more than 7 months after deposition. However, the film melted and was destroyed at the temperature about 20°C below the mp of the powder crystals (89°C).

View full abstract

Langmuir-Blodgett (LB) films of homologous series of simple amphiphilic compounds such as long chain fatty acids, alcohols, and esters have been investigated in order to clarify the factors governing the deposition type (X or Y) and their final structure (single or double layer, i. e., head-to-tail or head-to-head). These compounds play important roles as matrix materials to control molecular arrangement in constructing functional monolayer assemblies. From the measurement of transfer ratios in downward and upward trips, the X- and Y-types of film deposition were examined. While only Y-type deposition occurs with long chain acids and alcohols, both X- and Y-type depositions can be achieved with various long chain esters depending on physical conditions such as surface pressure, temperature, and dipping speed. X-ray diffraction patterns of the LB films were obtained by Weissenberg camera method. From the long-spacing values, single or double layered structure was determined. It has been found that LB films of long chain methyl esters take the head-to-head structure while long chain ethyl esters and acrylates have the headtotail structure, irrespective of deposition types. Thus, the final stable structure of a LB film seems to be determinedb y the hydrophilicityof. polar head groups. Theser esults provide a criterion for the selection of an appropriate matrix material to control the arrangements of functional molecules in the LB films.

View full abstract

Four azobenzene-linked amphiphiles which posseseel designed alkyl and methylene groups were synthesized. Properties of monolayers of these amphiphiles were studied by measuring their surface pressure-area isotherms. LB films were prepared on quartz plates by the Langmuir-Blodgett technique. The type of deposition was investigated by observing the decrease of surface area during transferring of the monolayer to a solid substrate, and the type of film was determined from the long spacing by X-ray diffraction. It was found that the type of deposition had a strong dependence on pH of the subphase. However, the type of film did not., always agree with the type of deposition but depended on the molecular structure of amphiphiles. The electronic spectra of the films were investigated. The comparison of the ratios of two absorption intensities of an azobenzene group gave the information on the orientation of the azobenzene group in amphiphiles. It was concluded that the arrangements of azobenzene-linked amphiphiles in LB films depended markedly on the length of alkyl and methylene groups.

View full abstract

Assembling and spectroscopic properties of mixed monolayers of 11-(9-carbazolyl) undecanoic acid (abbreviated to CUA) anr1 palmitic acid were studied. Surface pressure-molecu lar area isotherms for these mixtures at 15°C shown in Figure 1 indicated two kinds of monolay er structure above and below 13 mN.m^-1, respectively. UV absorption spectrum of built-up films was red-shifted as compared with that for CUA in hexane. This result su ggested the aggregation of carbazolyl chromophores, which was analyzed by the exciton in teraction model. The polarized absorption spectrum showed dependence on the incident an gle. The simulation of the incident angle dependence indicated that carbazolyl groups were alig ned in built-up films with a high degree of orientation with respect to the film surface. The fluorescence anisotropy ratio of built-up films excited at 342 nm was much smaller t han that of CUA in a dilute viscous solution, which was interpreted as a result of ene rgy transfer. All these results indicated the interaction of aligned carbazolyl chromoph ores, which should play an important role in electron or energy transfer reactions.

View full abstract

Electric-field-modulated optical absorption (EA) spectra, of merocyanine. dye Langmuir-Blodgett films have been measured to investigate the thin film structure. Bec ause of A considerable change in the permanent dipole moment of merocyanine dye between the excited state and the ground state, application of an external electric field gives rise to a large Stark shift of the molecular excitation energy. As a result, the EA spectra refle ct sensitively the orientation of molecular axis of chromophors in the LB films. The EA spectra have been measured for the longitudinal electric fie ld on two different configurations of LB films having either isolated monolayers or isolated paired layers of merocyanine dyes. From a Comparison of these spectra with calculated ones, it is conclude d that the J-aggregates in the Y-type layers are slightly different in energy. From the longitudinal and transverse EA spectra, the dipole moment change (Δμ) of chromophors between the excited and ground states is estimated for both configurations. it is concluded that the chromophors. are almost parallel to the layers, slightly inclined in the opposite directions on both sides of Y-layers.

View full abstract

Time dependence of the molecular aggregregation states of a neat merocyanine dye monolayer at air/water interface were investigated by in-situ observation of the absorption spectra of the monolayers prepared at various pH's and temperature conditions of the subphase. Jaggregation state was found to be formed immediately after spreading a chloroform solution containing the dye on the interface and to change gradually into the dimeric state. And the J-aggregate form disappeared eventually about one hour after spreading. At a lower pH, the J-aggregation state became less stable and changed to the dimeric form with the higher conversion rate. This suggested that Cd2+ ions might play an important role of bridging the carboxylic groups of the adjacent dyes in the J form and of keeping the Jaggregation state stable. The conversion rate was found nonexponential with respect to time. The temperature effects of the subphase on the rate gave interesting results. At higher temperatures the rate became faster after the J-band intensity had decreased to the one-third of the initial value. On the other hand, the rate showed a minimum value at 26°C in the initial stages. These phenomena may be caused by two competiting thermal effects, one of them being to make the J-aggregate unstable at high temperature and the other being to make it stable due to annealing. The chromophore orientation in the two aggregation states at air/water interface was examined by measuring polarized absorption spectra at the normal and oblique incidence. The transition dipole moment of the chromophore in the dimeric form was found more tilted vertically from the horizontal plane parallel to the interface than that in the J-aggregation form.

View full abstract

Photoelectric. conversion was studied with a mixed monolayer of arachic, acid and 3, 3'-dioctadecylthiacarbocyanine iodide in the. molar ratio 10: 1 on an Sb-doped SnO₂ semiconductor electrode prepared by the Langmuir-Blodgett technique. The absorption spectrum of the monolayer showed a, considerable dimerization of the dye in the monolayer, The appearance of the photocurrent action spectrum of the monolayer was very similar to that of the absorptio n spectrum. This indicates that both the photoexitation of the monomeric dye and that of the dimeric dye cause almost the same electron injection after all. However, this does not necessarily lead to the conclusion that the electron injection efficiency of the monomer and that of the dimer is nearly the same. The photocurrent must be given as a result of complicated processes which, involve, the two-dimensional energy transfer among the monomer and two types of dirpers. The intrinsic current, quantum, efficiency was measured for various electrode potential. It turned out that the onset potential of the, photocurrent was much positive (anodic) compared with the flat-band potential of the SnO₂ electrode. Some reasons for this finding are discussed.

View full abstract

A monolayer of amphiphilic nitroxide radical, 2, 2, 6, 6-tetramethy1-4-octadecyloxy-1piperidinyloxyl (TEMOPO), was spread on a water subphase and a surface pressure-area curve was recorded. The part of the curve corresponding to the liquid expanded state of the monolayer was simulated with an equation of state. Such monolayer films of TEMOPO were transferred onto surfaces of tin oxide electrodes prepared on glass plates by the Langmuir-Blodgett (LB) method under various values of controlled surface pressure. The transfer ratio was found to be more than O.95 when the surface pressure was higher than 15 mN/m. The electrochemical behavior of TEMOPO monolayers confined to the tin oxide electrodes was studied by cyclic voltammetry in 0.18 mol/dm³ H₂SO₄ solutions. The form of voltammograms was found to change from one electrode to another. The amount of charge for the oxidation of TEMOPO to its cation and that consumed during the re-reduction of the cation to TEMOPO were evaluated from graphical integration of the voltammogram for each electrode prepared. The amounts of charge were always smaller than those expected from the surface pressure-area curve (Fig.1). The above procedure was applied to mixtures of TEMOPO and (arachic acid icosanoic acid (AA)) in various molar ratios. Reproducibility of cyclic voltammograms was improved by the mixing with AA. The behavior observed for TEMOPO and its mixtures was completely different from that for LB monolayers of amphiphilic tris(2, 2'-bipyridine)ruthenium. Structure of the LB monolayers of TEMOPO and the mixtures was inferred from these observations.

View full abstract

A novel electrochemical photodiode was fabricated by depositing complex LB films which consist of an electron acceptor (A), a sensitizer (S), and an electron donor (D) amphiphile. In these amphipathic molecules, a viologen moiety acts as an A unit, a pyrene or a porphyrin moiety as an S unit and a ferrocene moiety as a D unit, respectively. By arranging these three units on a gold optically semitransparent electrode (AuOTE) regularly in space normal to the electrode surface, e. g. (A)/(S)/(D) or (D)/(S)/(A), the photoinitiated vectorial flow of electrons could be achieved and was detected as photocurrents in a photoelectrochemical cell. Not only three-layer systems, but also the stack of the multilayers of each components, e. g. in the form of [A][A][A]/[S][S][S][S]/[D][D][D] and [D][D][D]/[S][S][S][S]/[A][A][A] were examined. The photocurrent in the latter systems was high er than that in the former systems. The photocurrent had o pposite directions depending upon the spatial arrangement of [A], [S] and [D] units in the film and was in accordance with the energy level profile a cross the film.

View full abstract

Stable insoluble monolayers of 2-heptadecylimidazole (2-HI) at the air/water interface'are formed for the acidic substrate water below pH 5, but the monolayers become unstable above pH 7. This is ascribed to the lack of hydrophilic ability of imidazolyl head group, in alkali region. At lower pH of the substrate water, the 3-nitrogen atoms of imidazolyl rings are protonated and this contributes to the proper hydrophobic-hydrophilic balance of the monolayer molecules. But if there are silver ions of concentration of the order of 10^-6 mol/l (0.1 ppm) in the substrate water, monolayers become very stable even in the alkali region and the collapsing pressures rise up to 50 mM/m. The complex formation of 2-HI with silver ion was discussed by equilibrium constants of the complex formation, and the result was confirmed by the change of the silver ion concentration before and after the spreading of a monolayer. The extremely high local concentration of 2-HI in the surface phase contributes to the formation of the complex in such a low concentration of silver ion. The 2-HI monolayers can be deposited on a solid substrate only when a suitable amount of silver ion in the substrate water is present. The 2-HI-silver complex monolayer deposited as a Y-type LB film and the long spacing of the film, determined by the X-ray diffraction, was 5.52 nm which was almost twice the length of the 2-HI molecule. The IR absorption spectrum of the LB film on a CaF₂ substrate also confirmed the formation of the complex in the LB film.

View full abstract

Hexa-coordinate iron phthalocyanines were synthesized to prepare stable monolayers and highly oriented. Langmuir-Blodgett (LB) films. Monolayer of [{ N-docosyJ-4, 4'-bipyr idinium (1+)-N'} (pyridine) (phthalocyaninato)iron (II)] bromide [2] was formed at air-water interface and was depo sited onto a substrate as a Z-type film by vertidal lifting method, whereas LB film could not be obtained in the case of bis(pyridine)(phthalocyaninato)iron(II) [1] without long alkyl chains. From the X-ray diffraction measurement of [2] LB film, the d-spacing was 37±2A. From this, phthalocyanine rings were considered to be inclined at ca. 35 degrees against substrate. This result was in good agreement with those of polarized infrared absorption measurement and zero-bressureextrapolated area of π-A isotherm. These results also suggested overlap of phthalocyanine rings in LB film. The [2] LB film showed large anisotropy in electric conduction. that is, the conductivity along the direction parallel to the substrate was 10^-7±2S/cm, whereas that along the perpendicular direction was less than 10^-12S/cm. The conductivity along the parallel direction is higher than that of iron phthalocyanine and is comparable to those of one dimensional phthalocyanine-ligand polymers. This increase of conductivity is considered to be caused by the formation of π-orbital overlap of phthalocyanine rings to increase the conductivity.

View full abstract

As amphiphilic salcomine derivatives expected for an oxygen adducts, N, N'-disalicylidene-2-hexadecyl-1, 3-propanediamine complexes of cobalt(II), nickel(II) and copper (II) were synthesized and monolayers of these compounds were spread on distilled water. From the measurements of the surface pressure-area isotherms, it was found that the Co complex can form the most stable condensed monolayer. The Co and Ni complexes showed the limiting molecular area of about 65A² while the Cu complex gave about 98A², suggesting different orientations of the head group in the monolayers. Using the Langmuir-Blodgett method, the Y-type monolayer assembly of each complex can be obtained. The polarized UV, visible and IR spectra of the LB films suggested that the functional group of the Co and Ni complexes are oriented with the long axis parallel to the surface and the short axis nearly to vertical, whereas both axis of Cu complex are considerably inclined. Thus, the different orientations of the complex in the LB films of the amphiphilic salcomine derivatives can be realized by the choice of the proper metal species. This phenomenon is interesting for a model of dioxygen carriers in the biological systems.

View full abstract

In order to obtain stereospecific coordination polymers, the monomolecular film method was employed at the air/water interface. In order to predict the possibility of the succession, ΔH^Θ, ΔG^Θ for tr ans→cis transformation was estimated from the infrared spect ra change of a free ligand, N, N'-didodecyldithiooxamide [(C₁₂H₂₅)₂dtoaH₂]. The transformation en ergy, 10 kJ.mol^-1, is smoller than the hydrophobic energy of the dodecyl chain. that is, the attempt to prepare the stereospecific polymers at the interface seems to be reasonable. The gathered films of the coordination polymers, (R₂dtoaCu), from a wide (air/copper aqueous solution) interface of the trough were subjected to the futher series of measurements: CHN analyses, IR spectra, magnetic susceptibility, electric conductivity, and differential thermal analysis. The results were discussed in comparison with those fro m the corresponding specimen prepared by an ordinary method of mixing bulk solut ions of the components as follows where R=C₆H₅CH₂, cyclo-C₆H₁₁ C₁₂H₂₅ and C₁₂H₂₅OCOCH₂. 1. the molar ratio of ligands to Cu²⁺ ion in the four coordination polymers of film type was found to be the same as that in the preparation by the bulk type, 2. in the films some IR peaks (860 and 870 cm^-1) which are related to CS stretching of the trans-form in the bulk type specimens with C₁₂H₂₅ or C₁₂H₂₅OCOCH₂ substituents (Figs.2C and 2D)are disappeared, 3. the two substituents of compounds described above are more hydrophobi c than the other two, 4. the results of magnetic measurements suggest their cis-form in the hydrophobic couple of the coordination polymers (Figs.3 C and 3 D).

View full abstract

Stable monomolecular films of diicosyl 3, 3'-(m- and p-phenylene)bis[trans-acrylate] ([I]and [II]) were prepared on the water surface in spite of the absence of ionic or hydrophillic functional groups. The limitting molecular areas of these films are 41 and 62A² at 17°C, respectively. These films showed different photochemical reactivity depending on the degree of compression. at the liquid condensed state, photochemical cross-linking associated with remarkable expansion of the film, and at the solid condensed state, hydrolysis associated with contraction of the film were observed. These monolayers were successfu lly deposited on a solid substrate as Y-type films [I]or Z-type films [II] and the deposited films showed photochemical cross-linking to give insoluble films and soluble oligomers. These LB films gave tou gh electron beam resists of negative type with line width of O.14-0.85 μm under applied voltage of 5 kV with a beam diameter of 50A and irradiation speed of 3-33 m/s, while the cast films gave resists with broader wavy lines of 0.6-2.6 μm width and poor adherence.

View full abstract