Determination of Piezoelectric Fields Across InGaN/GaN Quantum Wells by Means of Electron Holography

Electron holography was used to determine the piezoelectric fields across an InGaN/GaN quantum-well structure. Holograms were taken with the sample intentionally tilted such that adjacent layers overlapped. The phase changes in the overlapping regions were analyzed to determine the piezoelectric fields in each well. It was shown that the piezoelectric field was strongest at the central part of the quantum-well structure. The field strength averaged over eight InGaN wells was ~2.2 MV/cm.     

Low‐resistive and transparent AZO films prepared by PLD in magnetic field

Al₂O₃‐doped ZnO (AZO) thin films have been deposited onto glass substrates using a split target consisting of AZO (1 wt%) and AZO (2 wt%) by pulsed laser deposition with an ArF excimer laser (λ = 193 nm, 15 mJ, 10 Hz, 0.75 J/cm²). By applying a magnetic field perpendicular to the plume, the lowest resistivity of 8.54 × 10^?5Ω·cm and an average transmittance exceeding 91% over the visible range were obtained at a target‐to‐substrate distance of 25 mm for approximately 279‐nm‐thick AZO film (1.8 wt%) grown at a substrate temperature of 230 °C in vacuum. From cross‐sectional TEM observations and the XRD spectrum, a reason why the low resistivity (54 × 10^?5Ω·cm) was reproducibly obtained was considered to be due to the fact that a disorder of crystal growth originating in the vicinity of the interface between the substrate and the film was suppressed by application of the magnetic field and the c‐axis orientation took preference, giving rise to the increase of mobility. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(2): 40–45, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20026     

A 513‐ppi FFS‐mode LCD using technique for changing part of active layer of oxide semiconductor to transparent electrode

We have established a technique for changing part of an active layer of an oxide semiconductor (OS) to a transparent electrode in order to achieve an aperture ratio of 50% or higher and a bezel width of 1 mm in an fringe field switching (FFS) mode LCD panel with a high resolution of 513 ppi. Furthermore, we have prototyped an LCD panel by examining a driving mode that enables low‐frequency driving.     

Comparative assessment of the efficiency of Fe-doped TiO2 prepared by two doping methods and photocatalytic degradation of phenol in domestic water suspensions

Fe-doped TiO₂ particles responding to visible light were synthesized by impregnation and calcination method using TiO₂ particle and Ti element, respectively. The optical and the chemical properties were characterized by measuring the X-ray diffraction (XRD) and UV–visible spectroscopy. The onset of absorption shifted to longer wavelengths on doping TiO₂ by the calcination process, which showed a better response as compared to the impregnation method. The photocatalytic reactivity was evaluated by the degradation of phenol with impregnated Fe-doped (0.5% w/w in Fe) and calcined Fe-doped (Fe_xTi_{1 x}O₂, x ¼ 0.005 (Fe/Ti molar ratio)) TiO₂ separately in distilled and tap water. The characterization results have confirmed the advanced possibility of correlation between photoactivity and the special property of sulfur-containing calcined Fe-doped TiO₂. In case of the coagulation of the undoped A-I and the Fe-doped B-I, the photoactivity showed a decrease due to the presence of natural electrolytes and due to the high pH of tap water, whereas in the case of the coagulation of calcined Fe-doped TiO₂ prepared from sulfides (Fe_xTiS₂), the photoactivity showed an increase. In this study, highest catalytic activity was found to be strongly dependent both on catalyst structure and on the type of water used.     

Degradation of direct‐tunneling gate oxide under hot hole injection

The degradation of ultrathin SiO₂ films accompanied by the hole direct tunneling is investigated using a substrate hot hole (SHH) injection technique. Hot holes from the substrate as well as cold holes in the inversion layer are injected into the gate oxides in p‐channel MOSFETs with p⁺ poly‐Si gates, while the gate bias is kept low enough to avoid simultaneous electron injection from the gate. During the SHH stress, in contrast to the case of thicker oxide films, a strong correlation is observed between the oxide film degradation and the injected hole energy, whereas no degradation occurs due to the hole direct tunneling from the inversion layer. These experimental findings indicate the existence of threshold energy for trap creation process, which has been predicted by the theoretical study of hole‐injection‐induced structural transformation of oxygen vacancy in SiO₂. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(4): 54–61, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.2008