MunPyo Hong

Poly(3,4-ethylenedioxythiophene) Derived from Poly(ionic liquid) for the Use as Hole-Injecting Material in Organic Light-Emitting Diodes.

We report that poly(3,4-ethylenedioxythiophene) derived from poly(ionic liquid) (PEDOT:PIL) constitutes a unique polymeric hole-injecting material capable of improving device lifetime in organic light-emitting diodes (OLEDs). Imidazolium-based poly(ionic liquid)s were engineered to impart non-acidic and non-aqueous properties to PEDOT without compromising any other properties of PEDOT. A fluorescent OLED was fabricated using PEDOT:PIL as a hole-injection layer and subjected to a performance evaluation test. In comparison with a control device using a conventional PEDOT-based material, the device with PEDOT:PIL was found to achieve a significant improvement in terms of device lifetime. This improvement was attributed to a lower indium content in the PEDOT:PIL layer, which can be also interpreted as the effective protection characteristics of PEDOT:PIL for indium extraction from the electrodes.

The Effect of Passivation Layers on the Negative Bias Instability of Ga-In-Zn-O Thin Film Transistors under Illumination

Ga-In-Zn-O (GIZO) thin film transistors (TFTs) with disparate passivation structures were fabricated and their stabilities were compared. The devices were subjected to a negative bias stress with simultaneous exposure to visible light. TFT that incorporates a dual passivation composed of a SiO x layer grown at a relatively high temperature with an additional SiN x film deposited shows only -0.8 V V th shift, whereas a -5.7 V shift was observed for a TFT covered by a single SiO 2 film. The device degradation is susceptible to the ability of protecting external moisture, which may adsorb on the surface of the GIZO semiconductor to create donor states therein.

Effects of Plasma Process Induced Damages on Organic Gate Dielectrics of Organic Thin-Film Transistors

The effects of plasma damages on the organic gate dielectric of the organic thin film transistor (OTFT) during the fabrication process are investigated; metal deposition process on the organic gate insulator by the plasma sputtering mainly generates the process induced damage of bottom contact structured OTFT. For this study, two different deposition methods (thermal evaporation and plasma sputtering) have been tested for their damage effects onto poly(4-vinyl phenol) (PVP) as organic gate dielectric. Unlike thermal evaporation, conventional plasma sputtering process induces serious damages onto the organic layer as increasing the surface energy, changing the surface morphology and degrading OTFT performances.

Wheat truncated hemoglobin interacts with photosystem I PSK-I subunit and photosystem II subunit PsbS1

Recently, the truncated hemoglobin gene (trHb) was discovered in plant species, however, its role has not yet been determined. In this study, the gene expression of wheat trHb (TatrHb) was analyzed under various biotic and abiotic stresses. TatrHb transcript levels increased in NaCl-treated leaves and gibberellic acid (GA3)-treated roots. In addition, sodium nitroprusside (SNP), a nitric oxide donor, induced an increase in TatrHb transcript levels in roots and leaves. A yeast two-hybrid assay (YIIH) was used to screen a hypoxia-treated wheat seedling library with the goal of determining the putative function of TatrHb. In this YIIH assay, photosynthesis-related genes that showed high homology to the Hordeum vulgare chloroplast photosystem I PSK-I subunit and Zea mays photosystem II subunit PsbS1 were detected and their interactions with TatrHb were confirmed. Subcellular localization of a TatrHb-green fluorescent protein (GFP) fusion protein and bimolecular fluorescence complementation (BiFC) assay suggested that TatrHb is involved in photosynthesis. The TatrHb-GFP fusion protein was localized in the plastids and the yellow fluorescent protein signal indicated that the TatrHb protein interacted with PSK-I and PsbS1 in the chloroplast.

Effects of dopant ion and Mn valence state in the La1−xAxMnO3(A=Sr,Ba) colossal magnetoresistance films

The structural and electrical properties of Mn-based colossal magnetoresistance (CMR) thin films with controlled tolerance factor and Mn ion valance ratio were studied using crystal structure and chemical bonding character analyses. La0.7Sr0.3MnO3, La0.7Ba0.3MnO3, and La0.82Ba0.18MnO3 thin films with different contents of divalent cations and Mn3+/Mn4+ ratios were deposited on amorphous SiO2/Si substrate by rf magnetron sputtering at a substrate temperature of 350 °C. The films showed the same crystalline structure as the pseudocubic structure. The change in the sheet resistance of films was analyzed according to strain state of the unit cell, chemical bonding character of Mn–O, and Mn3+/Mn4+ ratio controlling the Mn3+–O2−–Mn4+ conducting path. Mn L-edge x-ray absorption spectra revealed that the Mn3+/Mn4+ ratio changed according to different compositions of Sr or Ba and the Mn 2p core level x-ray photoelectron spectra showed that the Mn 2p binding energy was affected by the covalence of the Mn–O bond and...

Role of Adsorbed H

We investigated the variation of electrical performances of solution-processed zinc tin oxide thin-film transistors (ZTO TFTs) when their channel layer was exposed to ambient gases at room temperature. During our research, we observed that adsorption of H2O on the backchannel surface can act as an electron trap and/or donor, depending on the amount of H2O. In addition, we found that the abnormal behavior seen in the TFTs was caused by different rates of adsorption/desorption. Finally, the instability in the electrical characteristics of the ZTO TFTs caused by the ambient atmosphere can easily be reversed by vacuum seasoning.

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The authors report X-ray scattering experiments on phase-separated composite organic film (PSCOF) structures mixed with ferroelectric liquid crystals (FLCs). We discuss the effect of the local layer structure in a PSCOF cell on the ratio of the concentration between prepolymer and liquid crystals. The ratio of optimized concentration in terms of optical characteristics for a PSCOF liquid crystal display are 30 wt % for prepolymer (NOA65) and 70 wt % for FLCs (Felix). We found that the layer structure in a ferroelectric liquid crystal cell made of 30 wt % NOA65 and 70 wt % Felix is a tilted-bookshelf layer structure. The angles 15 and 17° are the tilted-bookshelf angles at 65 and 58 °C, respectively. These layer tilt angles are almost same as the molecular tilt angles of ferroelectric liquid crystals in the Sm C* phase. We understand that this result comes from compensating for layer buckling. We consider that the PSCOF-mode local layer structure is an excellent solution to the problem of zig-zag defects and mechanical shock for application in future televisions and plastic ferroelectric liquid crystal displays (FLCDs).

O on Transfer Characteristics of Solution-Processed Zinc Tin Oxide Thin-Film Transistors

Solar cells with multi-junction structures employing various band gap layers are nowadays issue to achieve higher efficiency. We have prepared neutral beam assisted CVD (NBaCVD) deposited a-Si:H which has different oxygen contents as reflector bias and termination capacitor. The oxygen supplied by sputtering of quartz tube(shied for internal ICP antenna) as control of self bias. To control self sputtering of quartz we attached optimized valued capacitor between ends of antenna and ground. As increase of reflector bias directly related the energy of hydrogen, which is reflected from reflector, is increase then the oxygen contents reduced and transform the film structure as amorphous to nano-crystalline. The FTIR, XPS, optical band gap show the changes of oxygen and a-Si:H state as effect of energetic hydrogen reaction with oxygen and Six-Hy bond.

X-ray Scattering Studies of Phase-Separated Composite Organic Film Cells

The investigations of etch characteristics and mechanisms for both In2O3 and SnO2 thin films in the HBr-based inductively coupled plasmas were carried out. The etch rates were measured as functions of gas mixing ratio (0%–100% Ar), input power (400–700 W), and gas pressure (4–10 mTorr) at fixed bias power (200 W) and gas flow rate [40 SCCM (SCCM denotes cubic centimeter per minute at STP)]. Plasma parameters and composition were determined using a combination of plasma diagnostics by double Langmuir probe and global (zero-dimensional) plasma model. The correlations between the behaviors of etch rates and fluxes of plasma active species allow one to infer both In2O3 and SnO2 etch mechanisms as the transitional regime of ion-assisted chemical reaction, which is controlled by neutral and charged fluxes together.

Oxygen elimination effect in silicon thin film by neutral beam assisted CVD system at room temperature

During the sputtering process, the bombardment effect of negative oxygen ions (NOIs) on the thin-film properties of amorphous indium gallium zinc oxide (a-IGZO) was investigated. The energies of NOIs determined by in situ ion energy analyses are in good agreement with the values obtained using the Meyer equation. Furthermore, we find that the energies of NOIs are sufficiently high to affect the lattice distortion and/or displacement in a-IGZO films. The overall analysis revealed that the bombardment of NOIs has a considerable effect on a-IGZO film properties. Our work demonstrates that the bombardment of NOIs is a crucial issue for achieving high-quality a-IGZO films.