Effect of Cu doping on the optical property of green synthesised l-cystein-capped CdSe quantum dots

In the present study, the synthesis of water-soluble copper-doped CdSe nanoparticles (NPs) via a low cost, facile, and environmentally benign method is reported. Simple reagents such as selenium powder, cadmium chloride, and copper sulphate were used as selenium, cadmium, and copper precursor, respectively, while l-cysteine was used as a capping ligand without the use of an additional stabiliser. The as-synthesised copper-doped CdSe NPs were characterised using ultraviolet (UV-Vis) absorption and photoluminescence (PL) spectroscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy. By varying the dopant concentration, the temporal evolution of the optical properties and the shape of the nanocrystals were investigated. The observation and the results showed that the colour of the solution changed rapidly from orange to black, and the PL shifted to a longer wavelength at the high dopant concentration. The micrographic images revealed that the as-synthesised materials are small and could be used for bio labelling.

Model of phosphorus diffusion in silicon for highly doped solar cell emitter layer

Purpose The purpose of this paper was the development of a model enabling precise determination of phosphorus concentration profile in the emitter layer of a silicon solar cell on the basis of diffusion doping process duration and temperature. Fick’s second law, which is fundamental for describing the diffusion process, was assumed as the basis for the model. Design/methodology/approach To establish a theoretical model of the process of phosphorus diffusion in silicon, real concentration profiles measured using the secondary ion mass spectrometry (SIMS) method were used. Samples with the phosphorus dopant source applied onto monocrystalline silicon surface were placed in the heat zone of the open quartz tube furnace, where the diffusion process took place in the temperature of 880°C-940°C. The measured real concentration profiles of these samples became template profiles for the model in development. Findings The model was developed based on phenomena described in the literature, such as the influence of the electric field of dopant ionized atoms and the influence of dopant atom concentration nearing the maximum concentration on the value of diffusion coefficient. It was proposed to divide the diffusion area into low and high dopant concentration region. Originality/value A model has been established which enabled obtaining a high level of consistency between the phosphorus concentration profile developed theoretically and the real profile measured using the SIMS method. A coefficient of diffusion of phosphorus in silicon dependent on dopant concentration was calculated. Additionally, a function describing the boundary between the low and high dopant concentration regions was determined.

Effect of Dopant Concentration of N, Fe Co-Doped TiO2 on Photodegradation of Methylene Blue under Ordinary Visible Light

The effect of dopant concentration on N, Fe co-doped TiO2 for photodegradation of methylene blue under ordinary visible light was investigated. The photocatalyst samples were prepared using solgel method with titanium tetraisopropoxide as precursor of titania. The dopant concentrations were varied from 0.50% and 1.0% and the calcinations temperature was fixed at 600oC. The prepared photocatalysts were characterized using XRD and FTIR to determine their physical properties. The results from XRD proved that photocatalyst with dopant concentration of 1.0% N, 1.0% Fe-TiO2 showing highly desirable properties in phase and crystal size. The results from FTIR revealed the presence of both the dopants in the samples. The effectivity of photocatalysts was tested by performing a standard batch photocatalytic degradation experiment with methylene blue as a model pollutant under ordinary visible light. The result showed that photocatalyst with high dopant concentration for both nitrogen and ferrum dopant (1.0 % N, 1.0% Fe-TiO2) yielded a maximum of 80.50% methylene blue degraded within five hours of irradiation time.

ZnO1−xSxNanosphere in Ferroelectric Liquid Crystal Matrix: The Effect of Aggregation and Defects on the Dielectric and Electro-Optical Properties

High concentration (5 wt %) ofZnO1−xSxnanosphere (NS) has been dispersed in the ferroelectric liquid crystal (FLC) to analyze the effect of high dopant concentration in the FLC matrix. The FLC molecules actively interact with the NS. The presence of NS enhances the photoluminescence of the pure FLC material due to the coupling of localized surface plasmon resonance from NS with FLC molecules. The high concentration of NS causes an aggregation in the FLC matrix and creates topological defects. The defects and aggregation cause the change in electro-optical and dielectric properties of the pure FLC material. The bigger size of NS as compared to the smectic layer separation causes the warping in the smectic layer. Semiconducting nature of NS also affects the conductivity of the pure FLC.

Sputtered Nb- and Ta-doped TiO2 transparent conducting oxide films on glass

Radio frequency (rf) magnetron sputtering is used to deposit Ti0.85Nb0.15O2 and Ti0.8Ta0.2O2 films on glass substrates at substrate temperatures (TS) ranging from ∼250 to 400 °C. The most conducting Nb-doped TiO2 films were deposited at TS = 370 °C, with conductivities of ∼60 S/cm, carrier concentrations of 1.5 × 1021 cm−3 and mobilities <1 cm2/V·s. The conductivity of the films was limited by the mobility, which was more than 10 times lower than the mobility for films deposited epitaxially on SrTiO3. The difference in properties is likely caused by the randomly oriented crystal structure of the films deposited on glass compared with biaxially textured films deposited on SrTiO3. The anatase phase could not be stabilized in the Ta-doped TiO2 films, likely because of the high dopant concentration.