Authors: Patrícia Nunes, Francisco Manuel Braz Fernandes, Rui Jorge C. Silva, Elvira Fortunato, Rodrigo Martins
599
Authors: Qiu Sun, Fu Ping Wang, Zhao Hua Jiang
Abstract: Ferroelectric lead zirconate titanate(PZT)thin films have attracted great attention because of
their potential applications in memory devices[1] due to their unique properties, for example, hysteresis
loop and high dielectric constant. To realize these memory devices, it is necessary to overcome the
reliability problems such as fatigue, retention and imprint. It is well known that lead base perovskite
family ferroelectric thin films with donor dopant such as La3+ and Nb5+ have improved the electrical
properties of PZT thin films effectively [2-3]. And it is proposed that the cation substitution could reduce
the number of defects such as oxygen vacancies, which could promote electrical fatigue and leakage
current of PZT ferroelectric thin films obviously. In the present study, rare earth Yb-doped lead
zirconium titanate (PYZT) nanocrystalline powders with a composition near the morphotropic phase
boundary (Zr/Ti=52/48) were prepared by a modified sol-gel method. DTA/TG and XRD were used to
determine the thermal and phase changes in the formation of PYZT crystalline powders. The effect of
Yb3+ cation substitution for Pb2+ cation on the microstructure of PZT was developed with XRD. The
grain size of PYZT nanopowders is about 40 nm determined by TEM.
223
Authors: Mitsuo Okamoto, Tsutomu Yatsuo, Kenji Fukuda, Hajime Okumura, Kazuo Arai
Abstract: From a viewpoint of device application using p-channel SiC MOSFETs, control of their
channel properties is of great importance. We aimed to control the electrical properties of 4H-SiC
p-channel MOSFETs through locating the p-type epitaxial layer at the channel area, so called
“epi-channel MOSFET” structure. We varied the dopant concentrations and the thickness of the
epi-channel layer, and investigated their electrical properties. In case of heavily doped epi-channel
samples, the devices indicated “normally-on” characteristics, and their channel mobility decreased
slightly in comparison with the inversion-type devices. As for lightly doped epi-channel samples, the
subthreshold current increased with thickness of the epi-channel layer keeping their “normally-off”
characteristics. Their channel mobility also increased with thickness of the epi-channel layer. The
peak value of field effect channel mobility of the sample with 2.5 μm thickness and 5×1015 /cm3
dopant concentration epi-channel was 18.1 cm2/Vs.
711
Authors: Xiao Cai Yu, Peng Fei Zhu, Kui Sheng Song, Dong Dong Hu, Qian Du
Abstract: The Fe3+-doped nano-TiO2 catalyst with various amounts of dopant Fe3+ irons was prepared by a sol-gel method. The products were characterized by XRD and SEM. The photocatalytic degradation of ammonia nitrogen in aquaculture wastewater was investigated by using Fe3+-doped nano-TiO2 under UV irradiation. In the experiment, the effect of Fe3+/TiO2 dosage, the ratio of dopant Fe3+, ammonia-N initial concentration, pH value, H2O2 volume concentration, and reaction time, respectively, on the removal of ammonia-N was investigated. The experimental results can be stated as follows: when the ratio of dopant Fe3+ was 0.25% wt, the dosage of Fe3+/TiO2 was 0.7 g/L, the initial concentration of ammonia-N was 10 mg/L, H2O2 volume fraction was 4 %, respectively, if the reaction time may last 4 h, the removal rate of ammonia-N was expected to reach 97.17 %.
2001
Authors: M. Rajendraprasad Reddy, Mutsumi Sugiyama, K. T. Ramakrishna Reddy
Abstract: Nickel-doped ZnO thin films with different Ni contents (0 - 15%) were deposited on glass substrate at 350°C by a spray pyrolysis technique. 0.1 M solutions of zinc acetate and nickel sulphate were used as the precursors with air as the carrier gas. The effect of Ni-doping on the structural and optical properties of the layers was evaluated using appropriate techniques. The X-ray diffraction studies revealed that nickel atoms were successively incorporated into ZnO host matrix without forming any detectable secondary phase. All the grown films were polycrystalline with the (002) plane as the preferred orientation and the peak position shifted towards higher diffraction angle with the increase of doping content in the films. The films had hexagonal shaped grains and the evaluated grain size varied in the range of 20 - 48 nm. The optical studies revealed a decrease of transmittance with the increase of Ni-doping content in the films and the evaluated energy band gap was found to be direct that decreased from 3.32 eV to 3.05 eV.
1423
