Papers by Keyword: Carbon Doping

Abstract: The influence of structural defects in the active layer of GaN-on-Si substrates on the vertical leakage current was studied. The structural defects were analyzed by analytical scanning electron microscopy by means of cathodoluminescence (CL). The leakage current was determined by vertical I-V measurements.Two possibilities were found, which give potential explanations for the variations of the vertical leakage current: i) Threading dislocations, which may partially form leakage paths, were detected by CL imaging. ii) Variations of the carbon doping, which is used to tune GaN to a semi insulating material were revealed by CL spectroscopy.

Abstract: The influence of carbon doping on tribological properties of CrCN Coating was studied through preparation of coatings deposited on single crystal silicon and M2 high speed steel(HSS) substrate using closed-field unbalanced magnetron sputtering ion plating technique. The friction coefficients were measured by pin-on-disc set-up. The microstructure and bond states of the coatings were characterized by X-ray diffraxtion(XRD), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). The results show that the friction coefficient of coating decreases from 0.75 to 0.38, the microhardness increases from 1930HV to 2302HV, and the specific wear ratio of the coatings decreases from 8.35110-5m3/Nm to 3.85910-5m3/Nm with the increasing of carbon target current(IC) from 0A to 1.5A. The analysis of microstructure shows that the coatings transform from crystalline state to amorphous state and the grain size of the coatings decreases with the increasing of carbon target current.

Abstract: Visible light-sensitive carbon doped titanium dioxide nanoparticles (C-TiO₂) were prepared by a sol-gel method. The carbon dopant was obtained from glucose. The dopant level incorporated into the TiO₂ lattice structure was varied by using different concentrations of the carbon source solution. The nanoparticles were characterized by X-ray diffraction (XRD), BET Surface area, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Scanning X-ray photoelectron spectroscopy (SXPS) and Diffuse reflectance spectroscopy (DRS). The presence of carbon in the TiO₂ lattice was determined by SXPS. The DRS results revealed that carbon doping reduced the band gap of TiO₂. Doping was also found to cause a reduction in the particle size of the TiO₂ nanoparticles and enhance anatase to rutile phase transformation. The photocatalytic activities of the prepared samples were evaluated by the photocatalytic degradation of methyl orange. The carbon doped TiO₂ showed a higher photocatalytic activity than degussa P25 and undoped TiO₂.

Abstract: In this paper, both the TiB₂/SiC bilayer films and the carbon-doped TiB₂ (TiB₂-C)/SiC bilayer films (SiC films as interlayer) were successfully deposited on quenched Cr12MoV steel substrate through magnetron sputtering technology, and the carbon-doping effect on microstructure and friction/wear properties of TiB₂ films were investigated. The results show that the doped-carbon presented in manner of sp³C-C and sp²C-C bonds i.e. DLC (diamond-like carbon). As sliding against steel balls under dry frictional condition, the doped-carbon strongly decreased the friction coefficient of the films and the material transfer from the friction pairs to the films. At the same time, the doped-carbon reduced the wear rate of the films, the wear rate of the TiB₂ films and the TiB₂-C films were both in the magnitude order of 10^{−5 mm3} m⁻¹ N⁻¹, this is due to more material transfer significantly adhered on TiB₂ films than on TiB₂-C films.

Abstract: TiO₂ doped with C was obtained by way of immersion and calcinations method by using citric acid (CA) as dopant material.，and characterized by using XPS、XRD, UV-Vis, FT-IR and SPS. The results of analysis and characterization showed that C substituted partial Ti atoms in the lattice of TiO₂ and formed Ti-O-C structure. The photocatalytic properties of C-TiO₂ photocatalysts had been evidently improved as a result of a noticeable shift to visible region and the enhancement of the charge separation efficiency. The doped carbon lowers the band gap and expends the absorption of visible light region. CO₂ was photocatalytically reduced to form HCOOH by the best C-TiO₂-3/1-600 nanoparticles under the irradiation of the simulated daylight lamp. Methanoic acid yield may achieve 2633.98μmol/g-Cat when irradiation time is six hours.