Polycarbonate Thin Films Research Articles

Alteration of optical and morphological properties of polycarbonate illuminated by visible/IR laser beams

In this paper we investigate the effects of visible to near infrared (NIR) laser illumination on the optical transmission (OT) and morphological (MC) alterations of thin, curved surfaces of polycarbonate (PC). The second harmonic of Nd:YAG laser (532 nm) and two diode lasers (665 and 980 nm) were used as illuminating sources. The morphological changes of the PC surfaces are determined using atomic force microscopy (AFM), demonstrating the appreciable changes caused by shorter wavelengths (higher energy). When analyzing the OT spectra of PC thin films, a measurable decrease in the OT of the PC samples which were illuminated by 532, 665 and 980 nm, in particular 532 nm, for energy densities greater than 25 J/cm2 can be seen.

Track-etched nanopores in spin-coated polycarbonate films applied as sputtering mask

Thin polycarbonate films were spin-coated on silicon substrates and subsequently irradiated with 1-GeV U ions. The ion tracks in the polymer layer were chemically etched yielding nanopores of about 40 nm diameter. In a second process, the nanoporous polymer film acted as mask for structuring the Si substrate underneath. Sputtering with 5-keV Xe ions produced surface craters of depth ∼150 nm and diameter ∼80 nm. This arrangement can be used for the fabrication of track-based nanostructures with self-aligned apertures.

Thin Film Elastic Modulus of Degradable Tyrosine-Derived Polycarbonate Biomaterials and Their Blends

The integrity, function, and performance of biomedical devices having thin polymeric coatings are critically dependent on the mechanical properties of the film, including the elastic modulus. In this report, the elastic moduli of several tyrosine-derived polycarbonate thin films, specifically desaminotyrosyl ethyl tyrosine polycarbonates p(DTE carbonate), an iodinated derivative p(I(2)-DTE carbonate), and several discrete blends are measured using a method based on surface wrinkling. The data shows that the elastic modulus does not vary significantly with the blend composition as the weight percentage of p(I(2)-DTE carbonate) increases for films of uniform thickness in the range of 67 to 200 nm. As a function of film thickness, the observed elastic moduli of p(DTE carbonate), p(I(2)-DTE carbonate) and their 50:50 by mass blend show little variation over the range 30 to 200 nm.

Surface plasmon scattering on polymer–bimetal layer covered fused silica gratings generated by laser induced backside wet etching

Large amplitude fused silica gratings are prepared by combining the UV laser induced backside wet etching technique (LIBWE) and the two-beam interference method. The periodic patterning of fused silica surfaces is realized by s-polarized fourth harmonic beams of a Nd:YAG laser, applying saturated solution of naphthalene in methyl-methacrylate as liquid absorber. Atomic force microscopy is utilized to analyze how the modulation amplitude of the grating can be controlled by the fluence and number of laser pulses. Three types of plasmonic structures are prepared by a bottom-up method, post-evaporating the fused silica gratings by gold–silver bimetal layers, spin-coating the metal structures by thin polycarbonate films, and irradiating the multilayers by UV laser. The effect of the bimetal and polymer-coated bimetal gratings on the surface plasmon resonance is investigated in a modified Kretschmann arrangement allowing polar and azimuthal angle scans. It is demonstrated experimentally that scattering on rotated gratings results in additional minima on the resonance curves of plasmons excited by second harmonic beam of a continuous Nd:YAG laser. The azimuthal angle dependence proves that these additional minima originate from back-scattering. The analogous reflectivity minima were obtained by scattering matrix method calculations realized taking modulation depths measured on bimetal gratings into account.

Energy‐transfer dynamics of blue‐phosphorescent iridium and rhodium complexes doped in fluorescent molecules

Abstract— The temperature‐dependent photoluminescence features of polycarbonate thin films doped with blue‐phosphorescent molecules, either bis[(4,6‐difluorophenyl)‐pyridinato‐N,C2′] (picolinate) iridium (Flrpic) or bis(2‐phenylpyridinato‐N,C2′) (acetylacetonate) rhodium [(ppy)2Rh(acac)], which have an equivalent triplet energy of 2.64 eV, have been studied. The photoluminescence intensity of the Flrpic‐doped polycarbonate thin film did not show any dependence on temperature. On the other hand, as for the (ppy)2Rh(acac)‐doped polycarbonate thin film, decreasing photoluminescence intensity with increasing temperature (especially above 100K) was clearly visible. These results reflect that the internal heavy‐atom effect of (ppy)2Rh(acac) is weaker than that of Flrpic. Furthermore, the steady‐state and time‐resolved photoluminescence spectra of tris(8‐hydroxyquinoline) aluminum (Alq3) thin films heavily doped with Flrpic or (ppy)2Rh(acac) (50 wt.%) at 8K was studied. It was found that the enhanced phosphorescence from Alq3 is mainly due not to the external heavy‐atom effect by doping with the phosphorescent molecule but to the exothermic triplet energy transfer from the phosphorescent molecule to Alq3.

Effect of thermal annealing on pore density, pore size and pore homogeneity of polycarbonate NTFs

When an energetic and electrically charged beam of particles penetrates a nonconducting material, like crystal, polymer, etc., a permanent change in the nature of the chemical matrix along its path occurs giving rise to damaged sites known as latent tracks having diameter of the order of 10 nm. These tracks show an enhanced chemical reactivity as compared to the surrounding material; and, on etching, the damaged sites are enlarged forming nuclear track filters (NTFs). The NTFs so formed find applications in the fields as nuclear physics, geology, radiation dosimetry, material research, medicine and environmental studies. The pore density and pore size homogeneity are important traits of NTFs. These NTFs are also employed for the production of micro/nanostructures through template synthesis which finds various applications for the fabrication of sensors, devices and in the field of opto-electronics. The pore size of the NTF is generally not uniform due to various reasons like material defects in solid state nuclear track detectors (SSNTDs), nonuniform flux density of irradiating beam, variation in the angle of exposure during irradiation, temperature gradient in the etching solution, etc. The present work reports the development of NTFs and study of the effect of pre-etch thermal annealing of irradiated polycarbonate thin films (SSNTDs) on the density and homogeneity of etched pores in developed NTFs. NTFs were developed by irradiating Makrofol (KG) with heavy-ion beam at the UNILAC, Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, Germany and then chemically etching of annealed and unannealed irradiated samples. The pore size, pore density and pore size homogeneity of the NTFs were compared for annealed and unannealed samples. The study indicates decrease in pore size, pore density and increase in homogeneity of pores with post-irradiation and pre-etch thermal annealing. The uniformity of the pores of NTF will lead to uniformity of micro/nanostructures fabricated by using the pores as templates. These uniform micro/nanostructures can act as excellent charge sprayers in the cold cathode emitters.

Microbeam analysis of yellow sand dust particles

AbstractA microbeam system was applied to analyses of yellow sand dust particles. Such particles from the Asian continent sometimes cause turbid conditions in Japan, especially in spring, and are sometimes changed by mixing with anthropogenic and marine aerosols. For better understanding of their formation mechanism, analysis of single particles is indispensable. For this purpose, we developed a microbeam analysis system at Tohoku University with a spatial resolution of better than 1 µm. The system comprises two x‐ray Si(Li) detectors for particle‐induced x‐ray emission (PIXE), an annular ion‐implanted Si detector for Rutherford backscattering (RBS), an ion‐implanted Si detector for off‐axis scanning transmission ion microscopy (STIM), and a Si‐PIN photodiode for direct STIM analyses. The combination of PIXE, RBS and off‐axis STIM methods enabled simultaneous analyses of hydrogen to metal elements and revealed the chemical compositions of these particles. Yellow sand dust particles were impacted on a thin polycarbonate film and analyzed using the microbeam analysis system. After quantification of the elemental components of these particles, the chemical composition of each particle was obtained. Silicon, calcium, oxygen, carbon, and hydrogen are the main composing elements of the particles originating mainly from soil dust from the Asian continent. The particles contain sulfur and heavier elements too, originating from mixing with anthropogenic aerosols. Sodium, magnesium, and chlorine, which come from marine aerosols, are also included in these particles and might be adsorbed during transport from the Asian continent. Single particle analysis of yellow sand dust will engender a better understanding of their formation process during transport. Copyright © 2008 John Wiley & Sons, Ltd.

Poly(methyl methacrylate) microchip device integrated with gold nanoelectrode ensemble for in-column biochemical reaction and electrochemical detection

This paper proposes a poly(methyl methacrylate) (PMMA) based microchip with an integrated gold nanoelectrode ensemble (GNEE) and a quartet-T loading channel for in-column urea/urease reactions and electrochemical detections. The on-chip GNEE electrode is fabricated using an electrodeless deposition process on a thin polycarbonate (PC) film and bonded directly onto a PMMA substrate to carry out high-performance electrochemical detections. The in-column bio-catalytic reaction of urea/urease is successfully demonstrated utilizing a novel approach based on the different electrokinetic mobilities of urea and urease in capillary electrophoresis (CE) channel. The experimental results significantly show that the GNEE electrode provides a better detection response for the reaction product of ammonia (NH 4 +) than a conventional planar gold electrode. The detection results demonstrate a satisfactory determination coefficient ( R 2 value) and high reproducibility with a detection limit of 14.8 and 62.8 μM while detecting standard ammonia solution and the urea/urease reaction product of NH 4 +, respectively. These results confirm the capability of the proposed device for the high-resolution CE-electrochemical detection (CE-ED) of bioanalytical reactions.

Surface and Bulk Structure Characterization of Proton (3 MeV) Irradiated Polycarbonate

Polycarbonate (Makrofol‐N) thin films were irradiated with protons (3 MeV) under vacuum at room temperature with the fluence ranging from 1×1014 to 1×1015 protons cm−2. The change in surface morphology, optical properties, degradation of the functional groups, and crystallinity of the proton‐irradiated polymers were investigated with atomic force microscopy (AFM), UV‐VIS, and Fourier‐transform infrared (FTIR) spectroscopy, and X‐ray diffraction (XRD) techniques, respectively. AFM shows that the root mean square (RMS) roughness of the irradiated polycarbonate surface increases with the increment of ion fluence. The UV‐VIS analysis revealed that in Makrofol‐N the optical band gap decreased by 30% at highest fluence of 1×1015 protons cm−2. The band gap can be correlated to the number of carbon atoms, M, in a cluster with a modified Robertson's equation. The cluster size in the proton‐irradiated Makrofol‐N increased from 112 to 129 atoms with the increase of fluence from 1×1014 to 1×1015 protons cm−2. FTIR spectra of proton (3 MeV) irradiated Makrofol‐N showed a strong decrease of almost all absorption bands at about 1× 1014 protons cm−2. However, beyond a higher critical dose an increase in intensity of almost all characteristic bands was noticed. The appearance of a new peak at 3,500 cm−1 (‐OH groups) was observed at the higher fluences in the FTIR spectra of proton‐irradiated polycarbonate. XRD measurements showed an increase of full width at half maximum (FWHM) and the average intermolecular spacing of the main peak, which may be due to the increase of chain scission and the introduction of ‐OH groups in the proton irradiated polycarbonate.

Single shot measurements of laser driven shock waves using ultrafast dynamic ellipsometry

Ultrafast dynamic ellipsometry, a diagnostic that measures both the shock-induced optical effects and the motion of shocked materials, has been implemented in a single shot form. This is accomplished using chirped pulse interferometry and probing the sample at two angles with both s- and p-polarized light. The application of single shot ultrafast dynamic ellipsometry should prove important in future studies of shocked transparent materials and metals because it allows concurrent determination of the initial and shocked optical constants, shock and particle velocities, and the picosecond time dependence of these properties with a higher signal-to-noise ratio and less stringent sample requirements than multishot methods. The ability to infer both the initial and shocked refractive indices of the material eliminates the need for performing extra experiments to calibrate the window, greatly simplifying the analysis and making each shot a self-contained experiment. The implementation of this diagnostic is described, and its utility is demonstrated on a shocked thin film of polycarbonate. Analysis of the data employs a multilayer thin film model to calculate the reflectance as a function of the time-dependent layer thicknesses and optical properties. Hugoniot data for the thin film polycarbonate is presented along with the effect of shock compression on the refractive index, which is consistent with the Gladstone-Dale relation.

Structural characterization of swift heavy ion irradiated polycarbonate

Makrofol-N polycarbonate thin films were irradiated with copper (50 MeV) and nickel (86 MeV) ions. The modified films were analyzed by UV–VIS, FTIR and XRD techniques. The experimental data was used to evaluate the formation of chromophore groups (conjugated system of bonds), degradation cross-section of the special functional groups, the alkyne formation and the amorphization cross-section. The investigation of UV–VIS spectra shows that the formation of chromophore groups is reduced at larger wavelength, however its value increases with the increase of ion fluence. Degradation cross-section for the different chemical groups present in the polycarbonate chains was evaluated from the FTIR data. It was found that there was an increase of degradation cross-section of chemical groups with the increase of electronic energy loss in polycarbonate. The alkyne and alkene groups were found to be induced due to swift heavy ion irradiation in polycarbonate. The radii of the alkyne production of about 2.74 and 2.90 nm were deduced for nickel (86 MeV) and copper (50 MeV) ions respectively. XRD analysis shows the decrease of the main XRD peak intensity. Progressive amorphization process of Makrofol-N with increasing fluence was traced by XRD measurements.

Opto-structural characterization of proton (3 MeV) irradiated polycarbonate and polystyrene

Polycarbonate (Makrofol-N) and polystyrene thin films were irradiated with protons (3 MeV) under vacuum at room temperature with the fluence ranging from 1×10 14 to 1×10 15 protons cm −2. The change in optical properties, degradation of the functional groups and crystallinity of the proton-irradiated polymers were investigated with UV–vis, Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) techniques, respectively. The UV–vis analysis revealed that the optical band gap of irradiated Makrofol-N is reduced by 30% as compared to 27.5% in polystyrene at highest fluence of 1×10 15 protons cm −2, owing to higher electronic energy loss of protons in Makrofol-N. The calculations of the number of carbon atoms per conjugation length, N and number of carbon atoms per clusters, M embedded in the network of polymers further revealed that Makrofol-N is more modified as compared to polystyrene on proton irradiation. FTIR results reveal the reduction in absorption intensity of the main characteristic bands of both the polymers after irradiation. The proton-irradiated Makrofol-N shows a strong decrease of almost all of its characteristic absorption bands at about 1×10 14 protons cm −2. Beyond a critical dose an increase of almost all its characteristic bands are noticed, however, no such effect had been observed in polystyrene at this particular fluence. Appearance of new –OH groups was observed at the higher fluences in the FTIR spectra of both proton-irradiated polymers. XRD measurements show the decrease of the main peak intensity and the crystallite size, confirming the increase of amorphization in polymers under irradiation.

Efficient Dual-Function Solar/Electric Light Guide to Enable Cost-Effective Core Daylighting

As a component of our cost-effective core daylighting research program, we have developed a hollow light guide that can be used to distribute sunlight collected by a heliostat device, and can also operate as an efficient fluorescent light fixture when the sunlight is insufficient to illuminate the workspace. This dual-function prism light guide structure has a cross-section that is similar to standard commercial fluorescent light fixtures, but with an increased depth in order to pipe the sunlight. The bottom surface of the guide is lined with a thin polycarbonate film having prismatic surface features, while the top and sides are lined with a highly-reflective multilayer optical film having a luminous reflectance greater than 98 percent. The angular constraints of the concentrated sunlight, combined with the high reflectance of the surfaces, enable the sunlight to be efficiently transported within the guide along a distance of greater than 10 m. The guide can also illuminate the room using electric sources, since the light from the lamps strikes the prismatic bottom surface at angles for which it is an efficient transmitter. Photometric characterization of the new dual-function guide has been performed, resulting in illuminance levels, uniformity and efficiency values well within recommended standards. The dual-function design approach has yielded a daylighting system that can be cost-effectively incorporated into standard office building construction.

Nanoscale thermal lithography by local polymer decomposition using a heated atomic force microscope cantilever tip

Nanopatterning of polymer thin films is the basis for the vast majority of current microlithography processes used in integrated circuit manufacturing. Future scaling of such polymer patterning methods will require innovative solutions to overcome the prohibitively high tool and mask costs associated with current optical lithography methods, which will prevent their use in many applications. Scanning probe-based methods for surface modification are desirable in that they offer high resolution patterning while also offering the ability to perform in situ metrology. We report a new scanning probe lithography method that uses heated atomic force microscope cantilevers to achieve nanoscale patterning in thin polymer films via the local thermal decomposition of the polymer and in situ postdecomposition metrology. Specifically, cross-linked polycarbonate thin films are developed in this work and are shown to be excellent writing media for this process. This new method has the advantage that the tip can be heated and cooled on microsecond time scales and thus material can be removed and patterned without need for the disengagement of the tip from the polymer surface. This ability to write while the tip is constantly engaged to the surface offers significantly higher writing speeds for discontinuous patterns relative to other scanning probe techniques.

Dispersion of gold nanoclusters in TMBPA-polycarbonate by a combination of thermal embedding and vapour-induced crystallization

Gold nanoclusters can be dispersed into the surface of a bisphenol-A polycarbonate film by acetone vapour induced crystallization, an effect which has been demonstrated in a previous publication of our group. Gold nanoclusters were deposited by physical vapour deposition on an amorphous thin film of polycarbonate. After vapour induced crystallization these clusters were detected by depth profiling to be embedded into the surface, with a concentration maximum in a depth of approximately 100 nm. In this work, we replaced the BPA by the modified tetramethyl bisphenol-A polycarbonate, which shows a slower crystallization kinetics. A strong enhancement of the dispersion depth has been achieved by thermal pre-embedding of the clusters into the surface. Surface analysis by means of atomic force microscopy reflects the rearrangement of polymer material in the course of crystallization.

Coupled surface plasmon resonance on bimetallic films covered by sub-micrometer polymer gratings

Abstract Angular interrogation investigation of the rotated grating-coupled surface plasmon resonance was performed, via exciting plasmons on special sensing layers by a frequency doubled continuous Nd:Yag laser beam in Kretschmann arrangement. NBK7 glass substrates were evaporated by silver and gold layers having appropriate thicknesses to ensure a narrow plasmon resonance peak. Thin poly-carbonate films spin-coated onto the bimetallic layers were patterned by the fourth harmonic of a pulsed mode Nd:Yag laser applying a master grating-based interference method. The pulsed force mode atomic force microscopic investigation has shown the existence of a surface relief grating and a coexistent adhesion modulation having a period of 416 nm. The conditions of the grating-coupling effect were determined for shallow sub-micrometer polymer gratings, and secondary minima were detected on the resonance curves measured in presence of polymer patterns, according to the calculations. The indispensability of a minimal modulation amplitude and the existence of an optimal rotation angle of the grating grooves with respect to the plasmon propagation direction were experimentally proven. The position of the emerged secondary resonance minimum indicated that the average film thickness was decreased caused by material removal during the structure formation. It was shown by tapping-mode AFM that the sub-micrometer adhesion modulation resulted in periodic adherence of streptavidin in the structure’s valleys. The attachment of a small amount of protein was detected based on the shift of the secondary resonance peak. The capability of the polymer grating for sensitivity enhancement was demonstrated, proving that the secondary peak shift is highly sensitive to the protein concentration. The application of the polymer grating covered bimetallic films as transducing layers in novel bio-sensorization method based on rotated grating coupling is proposed.

Orientation of Metalphthalocyanine Molecule Deposited on Polycarbonate Thin Film

A polymer gate dielectric layer is important when making organic FET because all organic FETs require flexibility, the right weight, optical transparence and low cost. It has various applications such as organic LSI, organic logic circuits and new information tools. In this paper, copperphthalocyanine (CuPc), vanadylphthalocyanine (VOPc) and zincphthalocyanine (ZnPc), to represent the active layers of OFET, were deposited using vapor deposition on polycarbonate (PC) thin film and their morphologies and molecular orientations were investigated using X-ray Diffraction (XRD) spectrometer and UV/Vis spectrometer. Based on these results, the molecular orientations of CuPc, ZnPc and VOPc thin films deposited on PC thin film were shown to be perpendicular to the insulating thin film of the PC thin film.

A survey of indoor workplace radon concentration in Japan

Radon ( 222Rn) concentration was measured at indoor workplaces in Japan to estimate effective dose to the public from 222Rn and its progeny. Measurements were made from 2000 to 2003 at 705 sites in four categories of office, factory, school and hospital. Passive type Rn monitors equipped with two sheets of polycarbonate thin films for measuring radon concentrations were installed at observation sites and replaced every 3 months to observe seasonal variations in 222Rn concentrations. The range of annual mean 222Rn concentrations for all sites was 1.4–182 Bq m −3, with the arithmetic mean and standard deviation were 20.8 and 19.5 Bq m −3. Annual mean 222Rn concentration observed at office, factory, school and hospital were 22.6, 10.1, 28.4 and 19.8 Bq m −3, respectively. Seasonal variations in 222Rn concentrations at offices, schools and hospitals were similar to those found in dwellings, and variations in factories were similar to those found in outdoor environments. 222Rn concentration observed in every quarter period was found to decrease as follows: school > office > hospital > factory. The average effective dose to the public due to 222Rn was estimated to be 0.41 mSv y −1 weighted by the working population. Considering the 222Rn exposure in indoor workplaces, effective dose to the general public is estimated to be in the range from approximately 0.42 to 0.52 mSv y −1.

高分子ゲート絶縁膜を用いたフレキシブル有機電界効果トランジスタの作製

We have fabricated organic field effect transistors constructed with pentacene active layers grown by vacuum deposition, polycarbonate (PC) gate dielectric layers fabricated by spin-coating and polyethylene naphthalate thin films used as substrates. The surface morphology of PC thin films was observed by atomic force microscopy (AFM). It was confirmed that the surface morphology of PC thin films had smoothness at a molecular level, although there was a problem to keep a balance between insulation property and smoothness of the surface. From the performance of the obtained organic field effect transistor, the carrier mobility was estimated to be 0.7×10-3 cm2/Vs, the on/off ratio to be 102 and the sub threshold voltage to be 32 V.

Surface plasmon resonance spectroscopy on rotated sub-micrometer polymer gratings generated by UV-laser based two-beam interference

Abstract Two-beam interference method was applied to generate gratings having periods of 416 nm and 833 nm by the forth harmonic of a Nd:Yag laser on thin poly-carbonate films spin-coated onto silver layer-covered substrates. The dependence of the modulation depth on the fluence and number of laser pulses was investigated by atomic force microscopy. A secondary pattern appeared on very thin polymer layers thanks to the “p” polarized laser beam illumination induced self-organized processes. The conditions of the emergence of grating-coupling caused additional plasmon resonance peak were determined for the sub-micrometer periodic polymer gratings. Surface plasmon resonance measurements were performed in attenuated total reflection arrangement to determine the effect of the angle between the plasmon propagation direction and the polymer groves on the grating-coupling. The effect of the modulation depth on the grating-coupling caused additional resonance minimum was also analyzed. We found coupling phenomena according to our calculations, the differences between the measured and theoretically predicted resonance curves were explained by the scattering on the complex surface structure.