A comparative study of the electrical characteristics and device instabilities in InGaZnO thin-film transistors (IGZO-TFTs) with four different high-k gate dielectrics (Al2O3, HfO2, Ta2O5, and ZrO2) has been conducted. High-k gate dielectrics have a sufficiently low leakage current for the gate insulator of IGZO-TFTs and ZrO2 has the highest dielectric constant, followed by Ta2O5, HfO2, and Al2O3. However, the charge trapping in high-k gate dielectrics induced the bias stress instability and degradation of IGZO-TFTs over time. In particular, the positive bias stress (PBS) and positive bias temperature stress (PBTS) caused a large positive threshold voltage (V th) variation due to electron trapping, while the negative bias stress (NBS) and negative bias temperature stress (NBTS) brought about a much smaller V th shift. In particular, the Al2O3 and HfO2 gate insulators have significant threshold voltage shifts for the PBS and PBTS measurements. Among the four different high-k gate dielectrics, ZrO2 is the most promising high-k gate dielectric for the IGZO-TFTs because of its high dielectric constant, low subthreshold swing, high mobility, large drive current, small hysteresis, and high on/off current ratio.

Sesame (Sesamum indicum L.) is an important oilseed crop that possesses a wide spectrum of pharmacological activities. Many studies have been conducted to investigate its health-promoting effects. Compared to other plant oils, sesame seed oil is highly stable to oxidation and has been demonstrated to have protective effects against ischemia-reperfusion injury in the rat brain. However; the effects of defatted sesame seeds extract (DSE) have not been studied yet. The purpose of this study was to evaluate the protective effect of DSE against ischemia models. For in vitro ischemia, oxygen-glucose deprivation followed by reoxygenation (OGD-R, 4 h OGD followed by 24 h reoxygenation) in HT22 cells was used to investigate the protective effects on cell death and the inhibitory effects on lipid peroxidation. For in vivo ischemia, the middle cerebral artery occlusion (MCAo, 2 h of MCAo followed by 22 h of reperfusion) rat model was used. Twenty-two h after occlusion the rats were assessed for neurobehavioral deficit and infarct volume. DSE (0.1-10 microg/mL) significantly reduced the cell death and inhibited lipid peroxidation induced by OGD-R. DSE (30, 100 and 300 mg/kg, p.o.) given twice at 0 h and 2 h after onset of ischemia reduced brain infarct volume dose-dependently and improved sensory-motor function. The therapeutic time window of DSE (300 mg/kg, p.o.) was 2 h after MCAo in rats. In conclusion, our results show that DSE may be effective in ischemia models by an antioxidative mechanism.

Charge trapping and tunneling characteristics of silicon-nitride (Si3N4) layer with various thicknesses were investigated for applications of tunnel barrier engineered nonvolatile memory (NVM). A critical thickness of Si3N4 layer for suppressing the charge trapping and enhancing the tunneling sensitivity of tunnel barrier were developed. Also, the charge trap centroid and charge trap density were extracted by constant current stress method. As a result, the optimization of Si3N4 thickness considerably improved the performances of NVM.

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Charge trapping characteristics of asymmetrical tunnel barriers consisting of different dielectric materials were investigated for application of nonvolatile memory devices. A thin HfO 2 layer stacked on ultrathin SiO 2 layer (SiO 2 /HfO 2 tunnel barrier) revealed higher current sensitivity to applied gate voltage than the conventional single SiO 2 tunnel barrier. On the other hand, the electron trapping of the tunnel barriers increased with the thickness of HfO 2 layer. Thus, a thin HfO 2 layer is promising for the engineered tunnel barriers, while a thick HfO 2 layer is appropriate for charge trapping layers for high-integrated nonvolatile memories. Meanwhile, an ultrathin Al 2 O 3 /HfO 2 tunnel barrier also revealed good electrical characteristics and is suitable for low temperature fabrication process.