Claire Heck

Macroparticle-Free Ti–Al Films by Newly Developed Coaxial Vacuum Arc Deposition

Titanium aluminide thin films are deposited on glassy carbon substrates by the coaxial vacuum arc deposition process. A rod-shaped Ti–Al alloy is employed as the evaporation source. In our vacuum arc system, because the spatial position of plasma on the surface of the evaporation source can be controlled by pulsed arc discharge, the thickness of the Ti–Al film can be controlled at nanometer scale. Amorphous stoichiometric Ti–Al films are synthesized from one Ti–Al alloy target at room temperature by changing the number of pulses of the arc discharge. Multilayered Ti and Al films could also be fabricated by changing the target and the number of pulsed arc discharges.

Optical properties of carbon and carbon nitride films prepared by mass-separated energetic negative carbon and carbon nitrogen ions

Carbon and carbon nitride (CN) films were prepared under ultrahigh vacuum condition by ion beam deposition using isotopically mass-separated, energetic (50–400 eV) negative 12C2− and 12C14N− ions, respectively. The optical properties as well as structures and chemical composition of the films have been characterized and discussed as a function of the kinetic energy of C2− and CN− ions. The structures of carbon and CN films in this study were hydrogen-free amorphous carbon (a-C) like. The N/C composition ratio of the CN films was N/C∼0.4, although the arrival ratio of N/C was N/C=1. The CN film properties depended weakly on kinetic energy of CN− ions, while on a-C films there were kinetic energy dependence of C2− ions of optical constant observed.

Orientation of α-sexithiophene on friction-transferred polythiophene film.

Controlling the molecular orientation of the conjugated oligomer, α-sexithiophene (6T), is crucial to improve organic optoelectronic device performance. Most 6T molecules evaporated onto quartz and SiO(2)/Si substrates orient nearly perpendicular to the substrate. Here, we report the formation of oriented thin films of 6T on in-plane-oriented polythiophene (PT) films formed by the friction-transfer method. 6T was evaporated onto oriented PT films under vacuum. The films were investigated by polarized optical microscopy, polarized ultraviolet-visible light (UV-vis) absorption spectroscopy, and grazing incidence X-ray diffraction measurement (GIXD). In all spectra, larger absorbance derived from PT and 6T was observed, in parallel polarization to the friction direction, compared to that of orthogonal polarization. These results indicate that the 6T molecular axis is aligned in the friction direction (PT chain direction) of PT films. GIXD also confirmed that the 6T molecular axis was aligned parallel to the PT chain axis. In contrast, 6T molecules evaporated onto quartz and poly(ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-coated silicon substrates aligned nearly perpendicular to the substrate. These results indicate that oriented PT films induce 6T orientation parallel to the PT chain direction.

Hydrogen evolution from glycerol aqueous solution under aerobic conditions over Pt/TiO2 and Au/TiO2 granular photocatalysts

Hydrogen was efficiently evolved from glycerol aqueous solution upon vertical photoirradiation of a Pt/TiO2 or Au/TiO2 bed under aerobic conditions. Granular photocatalysts were easily deposited, leading to high H2 selectivity (80-95%), whereas glycerol oxidation with CO2 evolution became dominant when suspended powder photocatalysts were used.

Doped-Dye Orientation Relative to Oriented Polyfluorene Host Film

Polyfluorene oriented films produced by a friction-transfer method show polarized blue-light emission. A subsequent doping of some types of fluorescent dyes into the oriented films using a vapor transportation method resulted in polarized emission from the oriented polymer and from the doped dye. Polarized photoluminescence spectra from the polyfluorene films doped with oligothiophenes, quaterthiophene, and sexithiophene showed that these materials exhibit marked dichroism caused by the alignment of the oligothiophene molecules parallel to the polymer chain. We succeeded in extending the wavelength range of the polarized emission by doping fluorescent dye into the films.

White Polarized Electroluminescence Devices by Dye Deposition on Oriented Polyfluorene Films

White polarized electroluminescent (EL) devices were produced by deposition of α-sexithiophene (6T), which is an orange-emitting dye, on blue-emitting oriented poly(9,9-dioctylfluorene) (PFO) polymer films produced by the friction transfer method. The results showed that the color of the emitted light changed from blue to white with increasing 6T film thickness. In addition, good polarization of the light was observed, suggesting that 6T molecules are oriented parallel to the direction of the underlying PFO molecules.

Oriented Polyfluorene Films Dye-Doped for Whitening of Polarized Electroluminescent Devices

Whitening of the emission of electroluminescent (EL) devices was performed by doping α-sexithiophene (6T), which is an orange emitting dye, into blue emitting oriented poly(9,9-dioctylfluorene) (PFO) polymer films. These oriented PFO films were produced by means of the friction transfer method and the doping of 6T was performed by means of the vapor transportation method which is a solvent-free process. The excellent orientation of PFO films and of the doped 6T led to very good polarization of the light emitted by these EL devices.

Oriented Thin Films of Polyaniline by Friction Transfer Method

Oriented thin films of polyaniline (emeraldine base) were prepared by the friction transfer method by rubbing solid polyaniline against a glass substrate to form a thin coating film on the substrate. Characterization by polarized ultraviolet-visible-near infrared spectra showed the dichroic property of the films, suggesting that the polyaniline was oriented on the glass substrate. Hydrochloric acid treatment transformed the film into emeraldine salt without loss of orientation. Moreover, the oriented film of emeraldine base could be recovered by aqueous ammonia treatment of the emeraldine salt. The oriented film could also be doped with camphorsulfonic acid.

Study of Cr Silicide Formation on Si(100) Due to Solid-Phase Reaction Using Soft X-Ray Emission Spectroscopy

Cr silicide formation on Si(100) substrate is studied by means of an alternative analysis technique: soft X-ray emission spectroscopy (SXES). Intermixing between chromium and silicon is observed at annealing temperatures ≥400° C. A nondestructive depth profile analysis shows that CrSi2 grows homogeneously on Si(100) for specimens heat-treated at 450°C.

Whitening of Polymer Light-Emitting Diodes by Dispersing Vapor of an Orange Fluorescent Dye into a Blue-Emitting Polymer Film

Whitening of polymer light-emitting diodes (PLEDs) based on the blue-emitting poly(9,9-dioctylfluorene) (PDOF) films was possible by dispersing vapor of an orange fluorescent dye 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) into the film by means of the solution-free vapor transportation method (VTM). Devices prepared with this method showed good color stability with bias voltage increase, while those formed with conventional spin-coating, where dyes and polymers were mixed in a solution (solution-mixed), showed color change from yellow to white-yellow. The maximum luminance of the PLED formed by the VTM was higher than that formed by conventional spin-coating process.