Remanent polarization of evaporated films of vinylidene fluoride oligomers

A remanent polarization of 130±3 mC/m[2], large among the values reported for organic materials, and rectangular D–Ehysteresis curves were realized in synthesized vinylidene fluoride (VDF) oligomer [CF[3](CH[2]CF[2])[17]I]film evaporated onto a platinumsurface around liquid nitrogen temperature. The results suggested that the VDF oligomer film has an extremely high crystallinity, and the electric dipoles arrange almost perfectly perpendicular to the filmsurface, and that a Lorentz local field factor of ferroelectric VDF oligomer crystals is nearly zero. Moreover, the obtained value of the coercive field, which was larger than those of ferroelectric polymers, might be attributed to the steric hindrance arising from the existence of iodine atoms at the VDF oligomer chains

Preparation of Resilient Organic Electrochemical Transistors Based on Blend Films with Flexible Crosslinkers

Organic electrochemical transistors (OECTs) exhibit high biocompatibility and are expected to be applied in biological sensors. This study focused on crosslinking agents in blend films of a mixed conducting polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), and a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM), as channel layers to realize reversible temperature response. In addition to the conventional (3-glycidyloxypropyl) trimethoxysilane (GOPS) crosslinker, a poly(ethylene glycol) diglycidyl ether (PEGDE) flexible crosslinker was used to overcome the volume expansion caused by the temperature change. Structural analysis revealed that PNIPAM was segregated on the surface and that the PEGDE crosslinker increased the crystallinity of PEDOT. Blend films with binary crosslinkers (PEGDE and GOPS) exhibited reversible response to temperature cycling. Therefore, the use of a flexible crosslinker in functional blend films can facilitate the fabrication of biosensing OECT devices with higher resilience to the fluctuation of surrounding conditions

Classical nucleation theory applied to molecular orientations in vapor-deposited organic thin films

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Kinetics Study on Initial Growth Stage in Vapor Deposition of Organic Thin Film Using Quartz Crystal Microbalance

The deposition behavior of stearic acid evaporated in vacuum was observed using a quartz crystal microbalance technique, and the time evolution curves of the amount of admolecules in the initial growth were compared with a theoretical curve calculated using a rate equation proposed on the basis of physisorption. From the results, it was demonstrated that the proposed rate equation for the early stage of film formation well described the experimental results and the growth kinetics of organic thin films was dependent on the substrate temperature. Basic parameters for thin-film growth, such as the mean stay time on the substrate of deposited molecules, can be estimated from the fitting of the theoretical equation to the experimental results at each substrate temperature. It should be noted that the basic parameters were sensitive to a small change in substrate temperature.autho

Early stage growth process of dinaphtho[2, 3-b:2\u27, 3\u27-f]thieno[3, 2-b]thiophene (DNTT) thin film

Early stage growth process of Dinaphtho[2, 3-b:2\u27, 3\u27-f]thieno[3, 2-b]thiophenes (DNTTs) thin film was investigated using grazing incidence X-ray diffraction (GIXD) and surface morphology analysis using atomic force microscopy (AFM). The thin film growth conditions were controlled by the slow deposition method. The vertical orientation of DNTT was confirmed from the first layer growth by GIXD. The morphologies of first layer grains were universal in the growth rate range of 0.155 ML/min - 0.017 ML/min. In addition, the dependence of the nuclei density on the deposition flow rate indicates that the number of molecules required for nucleation is 2 molecules (dimers). This result indicates that fewer molecules are sufficient for nucleation in the case of DNTT compared to the pentacene thin film growth on SiO2

Efficient molecular emitter

We demonstrate extraordinarily spectrally selective narrowband mid-infrared radiation absorbance and thermal emittance with resonant peak FWHM ~ 124 nm at l = 5.73 mm, corresponding to a Q-factor of ~ 92:3. This was achieved by harnessing mode coupling between a plasmonic metal-insulator-metal (MIM) metasurface and molecular vibrational mode resonances, with coupling constants ranging from h ~ 3.9% to 6.6%. In addition, thermal radiation emissivity is in close accordance to the metamaterial absorbance spectrum, as described by Kirchhoff’s law of thermal radiation, and furthermore, emission was not angle dependent, unlike that exhibited by grating-based emitters. The experimentally investigated MIM structures remained stable up to a 250C heating temperature. MIM metamatrials with strong and spectrally tailored vibrational coupling behaviors represent a new paradigm in photo-thermal energy conversion. The experimentally observed pronounced resonant coupling behaviour was well described by finite-difference time-domain simulations of the plasmonic structure, where molecular vibration contributions were modeled using the Lorenz oscillator approximation

Hyperspectral Molecular Orientation Mapping in Metamaterials

The four polarisation method is adopted for measurement of molecular orientation in dielectric nanolayers of metal-insulator-metal (MIM) metamaterials composed of gold nanodisks on polyimide and gold films. Hyperspectral mapping at the chemical finger printing spectral range of 4–20 μμm was carried out for MIM patterns of 1–2.5 μμm period (sub-wavelength). Overlay images taken at 0,π4,π2,3π4 orientation angles and subsequent baseline compensation are shown to be critically important for the interpretation of chemical mapping results and reduction of spurious artefacts. Light field enhancement in the 60-nm-thick polyimide (I in MIM) was responsible for strong absorption at the characteristic polyimide bands. Strong absorbance A at narrow IR bands can be used as a thermal emitter (emittance E=1−R), where R is the reflectance and A=1−R−T, where for optically thick samples the transmittance is T=0