Papers by Keyword: Nitrogen Doping

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Authors: Ming Zhao, Da Ming Zhuang, Gong Zhang, Ling Fang, Min Sheng Wu
Abstract: The nitrogen-doped TiO2 thin films were prepared by mid-frequency alternative reactive magnetron sputtering technique. The N concentration of the nitrogen-doped TiO2 thin films was analyzed by XPS. And the absorption spectra of the films in ultraviolet and visible region were also investigated. The results show that the mid-frequency alternative reactive magnetron sputtering technique is a convenient method for growing TiO2-xNx. Annealing the nitrogen-doped TiO2 thin film in nitrogen atmosphere under 380°C is helpful for increase the concentration of nitrogen in the film, but the ratio of N2 in reactive gas is mainly influence the concentration of nitrogen in the Ti-N bond in the TiO2 film. The increase of the thickness of nitrogen-doped TiO2 films will enhance the absorbability of the film in the ultraviolet and visible region. The wavelength of the absorption edge of TiO2-xNx film with 1.5% nitrogen shift to 441nm from 387nm, which is the absorption edge for undoped TiO2 films.
Authors: Xiao Shan Tang, Da Li
Abstract: Nitrogen-doped titanium oxide (TiO2-xNx) films were prepared by an improved ultrasonic spray pyrolysis device with buty1 titanate as the titanium source and ammonia as the nitrogen source. X-ray diffraction technique, scanning electronic microscope and UV-VIS spectroscopy were applied to study the microstructure, surface morphology and optical properties of the resulting films. The XRD peak intensity of the as-prepared films decreased with the increasing of nitrogen content and increased with the increasing of temperature, which indicates that the N doping introduced defects or strain in the TiO2 film. The SEM results indicate that all the samples have a nano-sized uniform surface. The smallest band gap and best hydrophobicity are obtained at the nitrogen concentration of 4 at. % and deposited at 400°C. The blood compatibility of TiO2-xNx thin films was observed through platelet adhesion. The experiments results show that the amount of thrombus on the TiO2-xNx thin films is much less than that of pyrolytic carbon. The experimental results show that the nano-sized TiO2-xNx thin films will be a new kind of promising materials applied to artificial heart valve and endovascula stent.
Authors: Wen Teng Chang, Yu Ting Chen, Chung Chin Kuo
Abstract: Five-period hydrogenated silicon carbide (SiC) multiple quantum wells with silicon dioxide (SiO2) or silicon nitride (SiN) dielectric that were synthesized by high density plasma chemical vapor deposition were studied using photoluminescence (PL) spectroscopy to understand its blue shift. Rapid thermal annealing induced significant blue shifting in the PL spectra after fluorine ion implantation due to crystallization. The thinning of the SiC causes blue shift due to the quantum confinement effect. The higher PL intensity of the amorphous SiC:H in SiO2 than in SiC/SiN may be attributed to the high number of non-radiative sites on its surface. Annealing with nitrogen may cause impurities in SiC/SiO2, thereby broadening the PL peak.
Authors: J.C. Burton, F.H. Long, Yuri I. Khlebnikov, I.I. Khlebnikov, Mathew Parker, Tangali S. Sudarshan
Authors: Pawel Kwasnicki, Roxana Arvinte, Hervé Peyre, Marcin Zielinski, Sandrine Juillaguet
Abstract: This paper presents a comparative optical and vibrational spectroscopy study of diversely n-type 4H-SiC epilayers. It is shown that in order to determine the nitrogen doping in a wide range (1016 up to few 1019cm-3) the two techniques are complementary. Moreover only the LTPL provides the information about the compensation and nature of the dopant species.
Authors: A. Zeng, E. Liu, S. Zhang, S.N. Tan, L.X. Liu, J. Gao
Authors: Wei Guo, Qing Qing Miao, Gang Xin, Li Qiong Wu, Ting Li Ma
Abstract: Dye-sensitized solar cell(DSC) is a new type of photovoltaic device. This paper mainly describes the research results of the development of a novel nitrogen-doped photoanode for DSC in our group. Highly efficient dye-sensitized solar cells (DSCs) of 7.6-10.1% were fabricated using nitrogen-doped titania electrodes. The photoelectrochemical properties of the nitrogen-doped titania powder, film, and solar cell were systemically investigated. We confirmed the substitution of oxygen sites and oxygen deficiency with nitrogen atoms in the titania structure by X-ray photoemission spectroscopy (XPS). The UV-Vis spectra of the nitrogen-doped powder and film showed visible light absorption in the wavelength range between 400 nm and 535 nm. The results of the stability test indicated that the DSCs fabricated by the nitrogen-doped titania exhibited great stability.
Authors: Hai Zheng Song, M.V.S. Chandrashekhar, T.S. Sudarshan
Abstract: Application of dichlorosilane (DCS) in 4H-SiC epitaxial growth on 4° off-cut substrates has been studied. The effect of C/Si ratio and N2 gas flow rate on epilayer properties is investigated in detail. It is found that the C/Si ratio has a significant influence on the growth rate, epilayer surface roughness (step-bunching), conversion of basal plane dislocations (BPDs), and generation of morphological defects and in-grown stacking faults. A wide range of doping concentration from p- to n+ can be controlled in DCS growth. High quality 4° off-cut SiC epilayers are achieved for C/Si=1.3 – 1.8. Addition of N2 has no obvious influence on growth rate and defect densities. The BPD conversion greater than 99.8% is achieved independent of N doping without any pretreatment.
Authors: D. Siche, M. Albrecht, J. Doerschel, K. Irmscher, H. J. Rost, M. Rossberg, D. Schulz
Abstract: Planar defects have been found in nitrogen doped 2" 4H-SiC crystals grown on off-axis seeds. The doping level was 1×1019cm-3, which is below the critical one for the thermally activated cubic stacking fault formation in the 4H matrix. Planar defects in the doped region are nucleated on the whole seed surface outside the growth facet. They are coexisting 15R and 6H lamellas of unitcell height as revealed by means of luminescence and high resolution transmission electron microscopy. These inclusions are preferably formed at the rim of the growth facet, where polytype change occurs after switching off the nitrogen flow during growth.
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