Papers by Keyword: Doping

Abstract: The main focus of the research was to correlate the composition and sintering parameters with the microstructure and dielectric properties of Ta₂O₅ (Tantalum Oxide) doped BaTiO₃ (Barium Titanate) ceramics. Ta₂O₅ was doped at three different percentages viz. 0.5, 1.0 and 1.5 mole%. The doped samples were then sintered using both single and double stage sintering techniques. Thereafter field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) techniques were used to examine the structure of the samples with particular focus on the incorporation of Ta⁵⁺ions into the BaTiO₃ crystal lattice. Finally, the dielectric properties were analyzed using impedence analyzer and the relationship between the properties and structure of doped BaTiO₃ was established. From the research, it can be stated that double stage sintering yielded best dielectric properties. The best stable value of room temperature dielectric constant (k) of 19000 was obtained for 1.5mole % Ta₂O₅ doped BaTiO₃ sample, sintered at 1320°C for 0 hour and 1280°C for 6 hours due to the combination of high percent theoretical density (%TD) and optimum grain size. At a temperature range of 30°C to 60°C, this combination of composition and sintering parameters yielded dielectric constant in the range of 18000-19000.

Abstract: In this study, the photocatalytic degradation of methylene blue has been investigated using natural zeolite modified Mn-doped ZnO nanoparticles synthesized by co-precipitation method. Comparison of degradation efficiency demonstrated that natural zeolite modifiedMn-doped ZnO exhibited higher activity than bare Mn-doped ZnO.

Abstract: Specimens were prepared by burning mixtures containing CaCO₃ and SiO₂ in 3:1 stoichiometric ratio along with dopants at different temperatures. Formation of C₃S doped with SO₃, BaO and MgO was studied. The results show that the temperature of beginning formation for C₃S is 1380°C in the system, and there exist both C₃S and C₂S. SO₃, BaO and MgO can effectively stabilize the M₁ and M₃ type alites through substitution and interstitial imperfection, and make f-CaO content 8.68 wt% at 1450°C. C₃S doped with minor elements appears in the shape of six-party plate with the mean size of 17~30μm.

Abstract: Through a conventional ceramic process, Y₂O₃ and Sb₂O₃ co-doped ZnO-based varistors were prepared. The microstructure and electrical properties of the as-prepared varistors were investigated. Y₂O₃ could act as an inhibitor to the growth of ZnO grains when working with Sb₂O₃. The mean size of ZnO grains in the Sb₂O₃ and Y₂O₃ co-doped samples was smaller than those of the samples only added with Y₂O₃ or Sb₂O₃. And with appropriately increased ratio of Y:Sb, it would result in increased sample densification. When the doping level of Y₂O₃ was small, the nonlinear coefficient and breakdown voltage of the varistors would increase with increasing doping amounts of Y₂O₃, and the leakage current would decrease. However, when Y₂O₃ was doped without Sb₂O₃, both the nonlinear coefficient and breakdown voltage of the varistors would decrease sharply, thus the leakage current increase dramatically. The electrical properties of the Sb₂O₃ and Y₂O₃ co-doped varistors would be better than those of the samples only added with Y₂O₃ or Sb₂O₃, and when the Y:Sb atom ratio was 5, the nonlinear coefficients, breakdown voltages and leakage current of the varistors reached their optimum values of 777 V/mm, 23 and 0.17 mA/cm², respectively.

Abstract: Fe-Ce-Mn catalysts loaded on TiO₂-ZrO₂ materials were prepared by sol-gel method and then were investigated for low temperature selective catalytic reduction (SCR) of NO with NH₃. It was found that the NO conversions over Fe-Ce-Mn/TiO₂-ZrO₂ was slightly improved compared with that over Ce-Mn/TiO₂-ZrO₂. The results showed that 96% NO conversion was obtained over Fe-Ce-Mn/TiO₂-ZrO₂ with the molar ratio of Fe/Mn=0.3. A comparative study of Fe-Ce-Mn/TiO₂- ZrO₂ and Ce-Mn/TiO₂-ZrO₂ for NO conversions at 140°C in the presence of H₂O and SO₂ proved that Fe-Ce-Mn/TiO₂-ZrO₂ exhibited higher resistance to H₂O and SO₂ than that of without Fe catalysts. In addition, Fe-Ce-Mn/TiO₂-ZrO₂ presented 90.49% NO conversion after cutting off the injection of SO₂ and H₂O.

Abstract: A high inversion channel mobility is a key parameter of normally off Silicon-Carbide MOS field effect power transistors. The mobility is limited by scattering centers at the interface between the semiconductor and the gate-oxide. In this work we investigate the mobility of lateral normally-off MOSFETs with different p-doping concentrations in the channel. Additionally the effect of a shallow counter n-doping at the interface on the mobility was determined and, finally, the properties of interface traps with the charge pumping method were examined. A lower p-doping in the cannel reduces the threshold voltage and increases the mobility simultaneously. A shallow counter n-doping shows a similar effect, but differences in the behavior of the charge pumping current can be observed, indicating that the nitrogen has a significant effect on the electrical properties of the interface, too.

Abstract: This paper reviews some recent advances in the application of scanning probe microscopy (SPM) electrical characterization techniques to several critical surface and interface issues in SiC technology. High resolution carrier profiling capabilities in SiC of scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) were employed for several applications. These included two-dimensional (2D) imaging of doped regions in SiC devices (to be used as input for device simulations or as a feedback for device processing) and the quantitative evaluation of the electrically active profiles of P (or N) and Al implanted 4H-SiC after high temperature treatments. Furthermore, the electrical modification of the SiO₂/4H-SiC interface in MOS devices subjected to post-oxide-deposition treatments in NO or N₂O and POCl₃ have been investigated, providing quantitative information on the electrical activation of incorporated N or P in the few-nm-thick SiC interfacial region. The lateral homogeneity of metal/SiC interfaces was probed at nanoscale by conductive atomic force microscopy (CAFM), with a special emphasis given to the case of Schottky contacts on 3C-SiC, where the diode behaviour is strongly affected by the high density of electrically active defects in the substrate. Finally, CAFM has been employed to study the current transport in epitaxial graphene (EG) grown on 4H-SiC (0001), revealing the impact of the substrate morphology (terraces and steps or facets) on the local conductivity.

Abstract: The adsorption and doping of Pd atom on graphene have been investigated using density-functional theory. The structure, binding energy, Mulliken population, and density of states of Pd-graphene systems are calculated. For the adsorbed graphene, the bridge site is the most favorable adsorption site. The adsorbed and doped Pd atom can stay stably on graphene by donating their charges to graphene, resulting in the charge redistribution of graphene. After the Pd functionalization, the hybridization of states of Pd and C atoms can be observed, indicating strong interaction between them.

Abstract: The structures and optical performances of TiO₂ doped with 4^th periodic transition metal ions were investigated in this paper. The characterization results of X-ray photoelectron spectroscopy and X-ray diffraction showed that the transition metal ions existed in oxidative states, and composites formed because of the reaction between doped metal ions and TiO₂. The absorption spectroscopy of TiO₂ doped with zinc was mainly in ultraviolet region, close to that of the pure TiO₂. While for TiO₂ doped with other transition metal ions including V, Cr, Mn, Fe, Co, Ni and Cu ions, the absorption spectroscopies covered ultraviolet region and visible light region, much broader than that of the pure TiO₂.

Abstract: Lanthanum-copper Composite Oxide Compounds were prepared from lanthanum chloride (LaCl₃) and copper chloride (CuCl₂), and used sodium hydroxide (NaOH) as precipitating agent. The research results showed that: the best preparation condition, which is the copper content3%;water bath temperature,70°C; agitation time,2 hours; calcination temperature,400°C; calcination time,1hour.The adsorption capacity of adsorbent was 63.88mg/g in this state. Analysis results indicate that Copper-doped crystal form dense granule in favour of phosphate adsorption .And La₂O₃ is very important on removing the phosphate.