Papers by Keyword: N-Doping

Abstract: An exhaustive experimental study of the influence of C/Si ratio on voluntary incorporation of nitrogen (N) and aluminum (Al) in 4H-SiC thin films is presented. The films were grown by chemical vapor deposition (CVD) in a horizontal, hot wall CVD reactor on Si- and C-face substrates, under Si-rich and C-rich conditions. Under some conditions the observed variation of dopant incorporation with C/Si ratio could be clearly attributed to the site competition effects, while in several cases other mechanisms have to be taken into account.

Abstract: Nitrogen-doped nanoTiO₂ sol was prepared by sol-gel method. The obtained sol was coated onto glass substrates by spin coating method, followed by drying at low temperature and calcined at high temperature. The films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet-visible spectra (UV-Vis) . The XRD spectra showed that the crystal type of N-doped TiO₂ films was anatase. The SEM images showed that the surface of films were flat without obvious crack and average diameter was about 20 nm. The UV-Vis spectra showed that the absorbance of N-doped TiO₂ films at ultraviolet region increased. N-doping caused photocatalysis response wavelength to turn longer. The photocatalytic activity of N-doped TiO₂ films was researched through the degradation experiment of methyl orange under ultraviolet light. Higher photocatalytic degradation efficiency was exhibited compared to the pure TiO₂ films.

Abstract: The present work was dedicated to the tailored synthesis of TiO₂ nanopowders doped with nitrogen (called TiO_2−xN_x ) for the photocatalytic degradation of methyl orange. In particular, the systems were synthesized by a sol-gel combustion route starting from nitric acid and tetrabutyl titanate (Ti (OC₄H₉)₄) as raw materials. The powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), suggesting that anatase phase is obtained at pH value of 4-6 and the heat-treated temperatures as low as 425°C. The photocatalytic activities of the N-doped TiO₂ nanopowders were monitored from the results of the degradation rate of methyl orange (MO) under solar light irradiation. The dependence of dye degradation rate on photocatalyst amount and initial pH was investigated. Under solar light irradiation, the TiO₂ doped with 30% N exhibited the highest photocatalytic reactivity, which could be attributed to the structure of the combustion-synthesized catalyst and the change of the bandgap induced by nitrogen inclusion.

Abstract: Thin TiO2 films in-situ growth on titanium alloy substrate were prepared in 0.05 mol/L H2SO4 electrolyte using the micro plasma oxidation method. The photocatalytic properties of the prepared thin TiO2 films were invested using Rhodamine B solution as a target pollutant. In order to improve the photocatalytic properties of the obtained TiO2 films, different content NH3·H2O was added into the H2SO4 electrolyte and obtained the N-doped TiO2 films photocatalyst. The influence of the doping ions on the crystal phase composition and microstructure of the TiO2 films were investigated by scanning electron microscopy (SEM) and X ray photoelectron spectroscopy (XPS). The results show that TiO2 films have uniformly grown closely on the surface of titanium substrate with pore size of 100-200 μm. The degradation efficiency of the TiO2 thin film prepared in H2SO4 + NH3·H2O is higher than that prepared with H2SO4, the degradation efficiency can reach 99% after 75 min, which increase about 10% than that of the H2SO4 eletrolyte.

Abstract: The present study is an attempt to synthesize N-doped TiO₂ nanophotocatalyst using sonochemical method, having photocatalytic activity in the visible region. Non-metal doped nanocatalysts have been successfully synthesized and characterized structurally and physiochemically by using XRD, SEM, TEM, EDX, UV-VIS, FT-IR, Raman and PL. The photocatalytic activity of the synthesized photocatalyst was investigated for the degradation of 2-CP as model compound. The result confirms the successful synthesis of N-doped photocatalyst with particle size 34 nm having anatase phase and shows new peak in a visible region at 587 nm..

Abstract: Graphene is the thinnest 2-D material which can be regarded as a single layer of graphite. The unique electrical, mechanical and optical properties of graphene can be used in many technological applications. 2-D nanomaterials with semiconducting properties are of great interest since they can be applied in electronics industry. Pure graphene is a zerogap semiconductor or semimetal, since the electron states just cross the Fermi energy. However, the electronic properties of graphene can be tuned by doping boron or nitrogen atoms. Understanding the electronic properties in terms of density of states and band structure of doped graphene is of great relevance today. In our work, we have analyzed the electronic properties of boron and nitrogen doped graphene using Density Functional Theory (DFT). The stability and charge analysis of doped structures have been studied. The Local Density Approximation (LDA) calculations have been used to find the total energies of the structures. In addition to the electronics industry, doped graphene also has great potential to adsorb gas molecules. Therefore, we have analyzed the H₂ molecule adsorption in pure, B-doped and N-doped graphene.

Abstract: nano-sized TiO2 doped with different percentage of N was prepared quickly by sol-gel process，and the photocatalytic properties of degradation dyes wastewaters were studied under stimulant solar light irradiation in the ambient air. Some properties of photocatalysts were characterized by the means of XPS, UV-Vis ,XRD, and degradation loss. The results showed the catalytic activity was the best when the doped of nitrogen was 0.5% at calcinated 400°C，and the degradation of the methylene blue was almost completed.

Abstract: In this work, we investigate the effect of the N-doping on microstructure and electrical properties of chalcogenide Ge₂Sb₂Te₅ (GST) films for application to multilevel-storage phase change memory (PCM). Crystal size can be markedly reduced from 16 nm to 5 nm by N-doping into GST. The crystal growth suppression is believed to be controlled by distributed fine nitride particles. The resistivity of N-GST as a function of annealing temperature exhibits a gradual change due to the crystal growth suppression. The characteristics imply that N-GST is suitable for application to multilevel-storage PCM as the next-generation nonvolatile memory.

Abstract: Mesoporous anatase-TiO₂ nanoparticles mono-doped and co-doped with thulium and nitrogen were synthesized via a modified sol-hydrothermal method, and characterized by XRD, BET, XPS, FT-IR, DRS and PL techniques. The results showed that the Tm-doping inhibited both the transformation from anatase to rutile phase and the recombination of photogenerated electron-hole pairs, as well as increased the content of surface hydroxyl group, then improved the UV photoactivity of TiO2. The N-doping led to forming the N–Ti–O and N–O–Ti structures, which narrow the electronic band structure, then improved the photoactivity in the visible light region. However, the best visible light photoactivity for degradating methylene blue (MB) in aqueous solution was obtained in the N-doped sample instead of the co-doped sample, implying that no synergetic effect rises from Tm and N co-doping.

Abstract: The first-principle quantum mechanical method was used to investigate the structures and electric properties of N-doped. Doping of N atom to clusters is found to be energetically quite favorable except for n=16. Different from bulk material, the LUMO-HOMO energy gaps of the In_nSb_n (n=6-12,14,16,24) clusters are enlarged by doping of N. The analysis of the electron density of the HOMO and LUMO states was performed to understand the behavior .