Papers by Keyword: Doping

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Authors: Xuan Zhang, Masahiro Nagano, Hidekazu Tsuchida
Abstract: Morphologies of basal plane dislocations (BPDs) in 4H-SiC epilayers doped with nitrogen or aluminum are explained in detail. While BPDs in low N-doped or Al-doped epilayers show the morphology of gliding dislocations responding to stresses, BPDs in highly N-doped (≥1.0×1018 cm-3) epilayers appear different. Some of them are parallel to [11-20] while others are straight and tilt from [11-20]. Tilt BPDs were also studied by TEM. Factors that relate to such morphology are discussed.
Authors: T. Henkel, Yasuhito Tanaka, Naoto Kobayashi, Shin Ichi Nishizawa, Shunichi Hishita
Authors: Olena Okhay, Vitor M.X. Bergano, Ai Ying Wu, Paula M. Vilarinho
Abstract: Crystalline (Sr1-1.5xBix)TiO3 (SBiT) thin films (0.002 ≤ x ≤ 0.5) were prepared by sol-gel on Pt/TiO2/SiO2/Si substrates. Cubic monophasic SBiT films were obtained for samples with x ≤ 0.167. For films with x ≥ 0.267 a second phase identified as Bi4Ti3O12 was observed. The lattice parameter of SBiT films increases with increasing Bi content, similar to the variation observed in SBiT ceramics. No obviously variation of the grain size with the Bi content was observed. The dielectric constant ε´ at room temperature increases with increasing of Bi concentrations up to x ≤ 0.1. The loss tangent of Bi doped SrTiO3 films is approximately 0.05 and lower than undoped ST films at 10kHz. The higher values of ε´ of Bi doped ST films with x=0.1 and x=0.167 in comparison with undoped films may suppose the appearance of a dielectric anomaly at low temperatures, which will be dependent on the Bi content.
Authors: Zhen Ming Chu, Yan Xia Li, Xu Sheng Wang, Xi Yao
Abstract: This paper studied the mechanoluminescence of the CaAl2Si2O8:Eu2+x, Dy3+y phosphors. The crystal structure, photoluminescence (PL) and mechanoluminescent intensity of the phosphors were investigated. The emission peak of CaAl2Si2O8: Eux2+ had a redshift from 418 nm to 428 nm due to the increase of the crystal filed intensity around Eu2+ with the increase of Eu2+ ion content. The ML (mechanoluminescence) emission of CaAl2Si2O8:Eu0.01and CaAl2Si2O8:Eu2+0.01, Dy3+0.02 can be seen by the naked eyeswhen compressive loads were appliedon the samples. Whats more, the addition of Dy3+can increase the ML intensity of CaAl2Si2O8:Eu0.01. The ML and PL spectra of the sample CaAl2Si2O8:Eu2+0.01, Dy3+0.02 are identical, located at 428 nm.
Authors: Maher Soueidan, Gabriel Ferro, Bilal Nsouli, Nada Habka, Véronique Soulière, Ghassan Younes, Khaled Zahraman, Jean Marie Bluet, Yves Monteil
Abstract: Vapor-Liquid-Solid was used for growing boron doped homoepitaxial SiC layers on 4HSiC( 0001) 8°off substrates. Si-based melts were fed by propane (5 sccm) in the temperature range 1450-1500°C. Two main approaches were studied to incorporate boron during growth : 1) adding elemental B in the initial melt, with two different compositions : Si90B10 and Si27Ge68B5; the growth was performed at 1500°C; 2) adding B2H6 (1 to 5 sccm) to the gas phase during growth with a melt composition of Si25Ge75; the growth was performed at 1450°C. In most cases, the growth time was limited by liquid loss due to wetting on the crucible walls. The longer growth duration (1h) was obtained when adding B2H6 to the gas phase. In the case of Si90B10 melt, the surface morphology exhibits large and parallel terraces whereas the step front is more undulated when adding Ge. Raman and photoluminescence characterizations performed on these layers confirmed the 4H polytype of the layers in addition to the presence of B which results in a strong B-N donor-acceptor band. Particle induced γ-ray emission was also used to detect B incorporation inside the grown layers.
Authors: Hyung Il Park, Ju Min Lee, Ji Sun Park, Kyung Eun Lee, Sang Ouk Kim
Abstract: We present the remarkable performance improvement of organic solar cells upon incorporating N- or B-doped carbon nanotubes (CNTs) into the organic semiconductor active layer. A small amount (0.2-5.0 wt%) of doped multi-walled CNTs are added to the bulk-heterojuction of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61 (PCBM). Unlike undoped metallic multi-walled CNTs, which cause undesired electron-hole recombination, N- or B-doped CNTs uniformly dispersed in the active layer selectively enhance electron or hole transport, respectively, and eventually help carrier collection. Specifically, the incorporation of 1.0 wt% B-doped CNTs results in a balanced electron and hole transport and accomplishes a power conversion efficiency improvement from 3.0 % (conventional control cells without CNTs) to 4.1 %.
Authors: Jesse B. Tucker, E.M. Handy, Mulpuri V. Rao, O.W. Holland, Kenneth A. Jones, N. Papanicolaou
Authors: Kee Rong Wu, Chung Hsuang Hung, Chung Wei Yeh, Hao Cheng Chang, Jui Ching Sun
Abstract: Three types of visible-light enabled titanium oxide (TiO2) films deposited on indium tin oxide (ITO) substrates at different levels of doping nitrogen (N) and carbon (C) and sputtering power are investigated for their capabilities to both pollution control and splitting water on hydrogen production. All samples are similar in morphological and microstructural features, but differ in their interfacial phase and dopants. For the N,C-codoped TiO2 film prepared at a higher sputtering power, tin ions can permeate into the growing TiO2 film from the ITO substrate and promote the formation of crystalline Ti1-xSnxO2 layer. It shows the highest photocatalytic oxidation rate over methylene blue (MB) solution under ultraviolet and blue light irradiation, respectively. This is ascribed to the photosensitized carbon on the columnar grains, leading an increase in the MB adsorption capacity and light harvesting efficiency. Conversely, the N-TiO2 film prepared at a lower power exhibits the highest photocurrent density and hydrogen yield rate of which a higher Schottky barrier formed at the TiO2/ITO interface. This suggests that the interfacial properties of TiO2/ITO film and C-doping truly control its photocatalytic capabilities in addition to the well-known surface states.
Authors: Ji Chao Wang, Guang Ming Wu, Guo Hua Gao, Xiao Wei Zhou
Abstract: Vanadium oxide films were prepared via the sol–gel process and dip coating method, using V2O5 as raw materials and H2O2 (volume fraction 30) as the solvent. Mn and Ni ions were added to vanadium oxide sol to prepare doping vanadium oxide films. The films were characterized by atomic force microscopy, FT-IR, X-ray diffraction and electrochemical techniques. The add-on of Metal ions will not affect the morphology of the vanadium oxide films, but change the valence of vanadium ion and vanadium oxide crystal phase. Furthermore, cyclic voltammetry curves show that metal ions doping vanadium oxide films exhibit reversible electrochemical reaction. But electrochemical impedance spectroscopy indicates pure vanadium oxide film has a better diffusion rate.
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