Papers by Keyword: Doping

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Authors: Alexander Tkach, Branca Araújo, Paula M. Vilarinho
Abstract: The effect of the electric field on the dielectric response of the Sr1-xCaxTiO3 ceramic system was analysed and complemented by structural and microstructural studies. A monotonic decrease of the lattice parameter and an increase of the average grain size from 11 to 23 μm with increasing x were observed by X-ray diffraction and scanning electron microscopy analysis respectively. Samples with x = 0.003 and 0.01 reveal a monotonous increase of low-temperature dielectric constant, corresponding to an enhancement of the tunability and a reduction of the driving electric field at 10-30 K for x = 0.01. For Sr1-xCaxTiO3 ceramic samples with x = 0.04 and 0.10 the ferroelectric phase transition of around 20 K was observed together with the enhanced tunability of the dielectric constant at 30-85 K for x = 0.10.
Authors: Giorgio Lulli, Roberta Nipoti
Abstract: In this work under-mask penetration of Al+ ions implanted in 4H-SiC is investigated by computer simulation based on the Monte-Carlo binary collision approximation (MC–BCA). Results indicate that a small fraction of ions, implanted normal to a (0001) 4H-SiC wafer (8° off-axis towards the {11-20}), is scattered and become channeled in the <1120> directions perpendicular to the <0001> axis. Due to this phenomenon, doped regions with concentration ≤ 10− 4 of the peak value, may extend laterally for a few µm below the edge of a SiO2 mask.
Authors: Howatchinou Tossoukpe, François Valdivieso, Julien Bruchon, Sylvain Drapier
Abstract: This paper presents a level set framework for the modelling of doping effect during surfacediffusion phenomena in a granular packing. The molecular flux of the doped compound is related tothe chemical potentials of all the diffusion species. The evolution of the grain compact is simulatedin three dimensions, based on the resulting kinetic law relating the surface diffusion velocity to thethermodynamic driving force. An anisotropic adaptive mesh, based on the level set function propertiesis used to refine the mesh in the surroundings of the grain surface. The simulations have been perfomedby using parallel computing strategy.
Authors: Hans Eckart Exner, Günter Petzow
Abstract: Understanding porosity coarsening is essential for controlling the properties of sintered materials and for producing high density or near net shape parts. As porosity is interconnected up to relative densities in excess of 80% or even 95%, measuring, monitoring and modelling of the growth of individual pores is relevant only at very high relative densities. This paper tries to convey two essentials of porosity coarsening: (i) characterization of the geometry of the pore space in the lower range of densities is possible by using stereological parameters, and (ii) coarsening of porosity takes place during all sintering stages by various mechanisms. Porosity coarsening has been reported in metals, ceramics and glasses. Recent and classical approaches, experimental results with two dimensional model arrangements as well as computer simulations of formation and opening of particle contacts are discussed. The effect of porosity dimensions on the properties of sintered materials and measures for preventing and provoking porosity coarsening are briefly addressed.
Authors: James D. Oliver, Brian H. Ponczak
Abstract: A series of designed experiments have been conducted over a period of years in a multiwafer, planetary rotation, epitaxial reactor to quantify the effects of various epitaxial growth process parameters on the resulting SiC epitaxial layers. This paper summarizes the results obtained through statistically designed experiments varying process parameters and their resultant effect on the layer thickness, carrier concentration and the variability of these parameters wafer-to-wafer, and within a wafer.
Authors: Xia Cui, Yi Qi Sun, Rong Ma, Xu Chun Song
Abstract: In the present paper, the Co-doped Fe3O4 nanoparticles have been successfully synthesized by the co-precipitation process. The morphologies size of the Co-doped Fe3O4 nanoparticles were characterized using scanning electron microscopy (SEM). The structure of the products were characterized by Xray diffraction (XRD). The composition of the product was analyzed by energy dispersive X-ray detector (EDS). The results show that the phase structure of the Co-doped Fe3O4 nanoparticles is spinel Fe3O4 with the particle size ranging from 40 to 50 nm. The prepared Co-doped Fe3O4 nanoparticles electrode was then applied to detect hydrogen peroxide (H2O2) in 0.01 M pH 7.0 phosphate buffer medium.
Authors: Dmitriy Marinskiy, Alexander Savtchouk
Abstract: In this work we propose a novel approach to measuring doping concentration in SiC based on a micro-scale time-resolved corona-Kelvin technique. In this method corona charging of SiC surface into depletion is done within a micro size corona spot and a Kelvin-force micro-probe is used to measure surface voltage decay in the center of the spot. The voltage decay is due to charge decay due to surface diffusion producing analogy of voltage-charge scanning under the probe. We use 2D charge diffusion analysis to extract two parameters – 1) doping concentration in the SiC epitaxial layer and 2) diffusion coefficient of corona ions on the SiC surface. The micro-spot corona-Kelvin method demonstrated in this work shall prove of importance for testing of doping uniformity on micro scale and measurements on a small area in SiC production wafers.
Authors: Guo Xuan Xiong, Hai Qing Huang, Chuo Yang
Abstract: A ferrocenyl Schiff base monomer was synthesized through the condensation of ferrocenecarboxaldehyde and phenylenediamine under neutral conditions, and then been used to produce copolymer materials with terephthaloyl chloride monomer by the Friedel-Crafts method. The model compound and copolymer of a novel poly(ferrocene-Schiff base) and their charge transfer complex with iodine was successful obtained, their structures been characterized by 1H-NMR spectra, infrared spectra, and ultraviolet spectra. In addition, the effects of iodine doping degree on its structure was studied, the electrical measurement results showed its conductivity can be increased several orders of magnitude after doping with iodine, the maximum conductivity at room temperature is 3.17×10-4 S•cm-1.
Authors: Pradeepan Periyat, Binu Naufal, Sanjay Gopal Ullattil
Abstract: This review focuses on the recent developments of high temperature stable anatase TiO2 photocatalyst. Eventhough TiO2 exists in different forms anatase, rutile and brookite, anatase phase stabilization is often the key to obtain the highest photocatalytic performance for TiO2, particularly for the use as an antibacterial and self-cleaning coatings in high temperature processed ceramics. Different methods available for the anatase stabilization in literature are critically reviewed and emphasis is placed on relatively recent developments. Currently available methods of anatase stabilizations are classified in to four categories viz (i) doping with metal ions (ii) doping with non-metal ions (iii) co-doping with metal and non-metal ions and (iv) dopant free stabilization by oxygen richness. Further to this, the application of these high temperature stabilized anatase TiO2 photocatalyst on various ceramics substrates such as tile, glass and sanitary wares as self-cleaning and antibacterial coatings are also been briefly discussed.
Authors: A.N. Afaah, Zuraida Khusaimi, Mohamad Rusop
Abstract: This paper presents a review on synthesis, structure, and growth mechanisms of one-dimensional nanostructures of ZnO. Solution-based method is a potential deposition technique for large-scale production as its advantages; the low cost, the simplicity of experimental set-up, and the low operating temperature. Mist-atomiser technique is one of the solution-based methods in synthesizing optimized ZnO nanostructures. Doping will lead for better properties of ZnO, which result to wide application area. Nanostructured ZnO is important in promising areas of application which devices utilizing nanostructures such as gas sensors and solar cells, since it is fairly easy to fabricate such forms of ZnO nanostructures, which have good charge carrier transport properties and high crystalline quality.
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