W. A. Farooq

Modification of electrical properties of Al/p-Si Schottky barrier device based on 2′-7′-dichlorofluorescein

The charge conduction mechanism and electrical properties of Al/p-Si Schottky barrier device based on 2′-7′-dichlorofluorescein (DCF) were investigated by current density–voltage (J–V) and capacitance–voltage (C–V) methods. Thin film of DCF organic compound was deposited on p-Si substrate as an interfacial layer by spin-coating technique. The dark J–V characteristics indicate that the rectifying junction is formed at DCF/Al interface. The ideality factor and barrier height of the Al/DCF/p-Si Schottky diode are higher than that of Al/p-Si Schottky diode. The effect of the thickness of the DCF organic layer was investigated by evaluating electrical parameters, such as the barrier height, ideality factor, series resistance, and interface state density. It is seen that the thickness of the DCF layer significantly affects the electrical properties by influencing the space charge region of the Al/DCF/p-Si Schottky junction. The interface state density of the diode was determined using low-high frequency C–V plots and was of order of ≈1011 eV−1cm−2. The order of the interface state density of Al/DCF/p-Si is lower than most of metal/organic compound/inorganic semiconductor devices. The values of the barrier height of the studied diodes are significantly larger than those of conventional Al/p-Si Schottky diodes. The J–V curves in the reverse direction are taken and interpreted via both Schottky and Poole–Frenkel effects. Poole–Frenkel effect was found to be dominant in the reverse direction.The charge conduction mechanism and electrical properties of Al/p-Si Schottky barrier device based on 2′-7′-dichlorofluorescein (DCF) were investigated by current density–voltage (J–V) and capacitance–voltage (C–V) methods. Thin film of DCF organic compound was deposited on p-Si substrate as an interfacial layer by spin-coating technique. The dark J–V characteristics indicate that the rectifying junction is formed at DCF/Al interface. The ideality factor and barrier height of the Al/DCF/p-Si Schottky diode are higher than that of Al/p-Si Schottky diode. The effect of the thickness of the DCF organic layer was investigated by evaluating electrical parameters, such as the barrier height, ideality factor, series resistance, and interface state density. It is seen that the thickness of the DCF layer significantly affects the electrical properties by influencing the space charge region of the Al/DCF/p-Si Schottky junction. The interface state density of the diode was determined using low-high frequency C–V plo...

Elemental analysis of fertilizer using laser induced breakdown spectroscopy

In recent years, the use of fertilizers has increased to achieve high growth rate of agriculture products. With this increase the chemical impact of agricultural activities on the environment has also been enhanced. In order to keep the environment healthy, and clean, it is necessary to identify contaminants and characterize the sources of contamination. In this study, a comprehensive chemical characterization of a DAP fertilizer has been carried out using laser induced breakdown spectroscopy. Phosphorous, manganese, magnesium, iron, titanium, molybdenum, nickel, cobalt, aluminum, chromium, lead, and uranium traces are detected. Relative abundances of Phosphorous, manganese, magnesium, molybdenum, iron, titanium, nickel, vanadium, calcium, cobalt, cadmium, tin are 26.64, 17.75, 13 97, 8.25, 7.97, 7.11, 5.07, 3.15, 2.94, 1.94, 1,55, 1.73 percent, respectively, whereas relative abundances of sulfur, aluminum, chromium, lead, and uranium are less than 1% and their sum is 1.93% of the total sample.

Atomic f-value measurements of high Rydberg members by pulsed laser-based magneto-optical spectroscopy

The authors describe a novel experimental technique, based on synchronizing pulsed Bitter coils with pulsed tunable laser sources in the ultraviolet, which allows a Faraday rotation method, originally developed for accurate f-value measurements of high Rydberg members with synchrotron radiation to be extended, both in available magnetic field strength and in spectral resolution. By applying their technique, they have extended accurate measurements of f-values for the principal series of Ba I from around n=15, where earlier measurements by the hook method become inaccurate, to n=42, well beyond the present capabilities of alternative experimental methods. Similarly, they have extended earlier magneto-optical measurements for Sr I from n=25 to n=43. Advantages of the new experimental approach are discussed.

Structural and optical properties of pure and Ag doped ZnO thin films obtained by sol gel spin coating technique

Abstract We have investigated the influence of Ag doping on zinc oxide thin films. Pure and Ag doped, preferentially oriented transparent zinc oxide thin films were prepared by sol gel technique on a glass substrate using diethyl amine as a stabilizer. The X-ray diffraction analysis revealed that the films with hexagonal wurtzite type structure were polycrystalline in nature with a preferred grain orientation in the 101 direction. The crystallite sizes decreased from 34 nm to 27 nm after silver doping. Both photoluminescence and optical transmission measurements showed that the band gap increased after the Ag doping. The structure and optical characterization studies clearly indicated the incorporation of Ag in ZnO. Hence, the observed increase in the optical band gap and decrease in crystallite size can be directly attributed to the effect of Ag ion incorporation into the ZnO lattice.

Analysis of rocks around capital of Kingdom of Saudi Arabia using laser induced breakdown spectroscopy

We present laser-induced breakdown spectroscopic studies of variety of rock samples around capital of Kingdom of Saudi Arabia. The samples were collected from East, West, North, and South about 20 km from city centre. Nd:YAG laser (1064 nm) in conjunction with MS257 Spectrograph (Oriel instrument) equipped with ICCD camera is used to record the LIBS data. The emission spectra of these samples have been recorded as functions of laser irradiance. The elemental composition and the relative abundance in each sample are found to be quite different. Quantities of Iron, Calcium, Carbon, Silicon, Aluminum, and Oxygen are detected in these samples. In samples from East, West and South, Iron and Silicon dominates. Dominant elements from North are Calcium and Silicon. Presence of Oxygen proves the existence of oxides in all samples. The color of the samples indicates the presence of Goethite and Hematite, oxides of Iron.

Study of Bacterial Samples Using Laser Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) technique has been applied to investigate two different types of bacteria, Escherichia coli (B1) and Micrococcus luteus (B2) deposited on glass slides using Spectrolaser 7000. LIBS spectra were analyzed using spectrolaser software. LIBS spectrum of glass substrate was compared with bacteria spectra. Ca, Mg, Na, K, P, S, Cl, Fe, Al, Mn, Cu, C, H and CN-band appeared in bacterial samples in air. Two carbon lines at 193.02 nm, 247.88 nm and one hydrogen line at 656.28 nm with intensity ratios of 1.9, 1.83 and 1.53 appeared in bacterial samples B1 and B2 respectively. Carbon and hydrogen are the important components of the bio-samples like bacteria and other cancer cells. Investigation on LIBS spectra of the samples in He and Ar atmospheres is also presented. Ni lines appeared only in B2 sample in Ar atmosphere. From the present experimental results we are able to show that LIBS technique has a potential in the identification and discrimination of different types of bacteria.

Photovoltaic and Impedance Spectroscopy Study of Screen-Printed TiO2 Based CdS Quantum Dot Sensitized Solar Cells

Cadmium sulphide (CdS) quantum dot sensitized solar cells (QDSSCs) based on screen-printed TiO2 were assembled using a screen-printing technique. The CdS quantum dots (QDs) were grown by using the Successive Ionic Layer Adsorption and Reaction (SILAR) method. The optical properties were studied by UV-Vis absorbance spectroscopy. Photovoltaic characteristics and impedance spectroscopic measurements of CdS QDSSCs were carried out under air mass 1.5 illuminations. The experimental results of capacitance against voltage indicate a trend from positive to negative capacitance because of the injection of electrons from the Fluorine doped tin oxide (FTO) electrode into TiO2.

Structural changes in tin oxide thin film with laser exposure

The effects of laser irradiation on the surface, structure and optical properties of SnO thin films deposited on glass substrates using electron beam evaporation, are investigated. The thin film samples are irradiated using fundamental beam at 1064 nm from Q-switched Nd:YAG pulsed laser with different power densities. Structural morphology of the film is investigated using XRD patterns and AFM image. Both XRD pattern and AFM image show increase in grain size of the film with increasing laser power density. Other optical phenomena, photoluminescence emission, transmission, refractive index determination and optical band gaps calculations are also carried out at various laser power densities. Results from all these investigations reveal expansion in grain size of the crystalline SnO thin film with increasing laser power density.

Solar Light Photodetectors Based on Nanocrystalline Zinc Oxide Cadmium Doped/p-Si Heterojunctions

The transparent undoped and Cd doped ZnO thin films were deposited on p-type Si substrates to fabricate Cd-ZnO/p-Si diodes. The Cd doped ZnO thin films exhibited a polycrystalline structure. The transmittance measurements indicate that the films have transparency ranging from 47% to 92% for the UV and visible regions. The optical band gap of the films were found to be ranging from 3.27 to 3.19 eV with Cd content. The photoelectrical properties of the diodes under various illuminations were analyzed. The undoped and Cd doped ZnO thin films/p-silicon devices exhibit a photovoltaic behavior with the obtained photovoltaic parameters. The continuous distribution of interface states in the diodes is analyzed by capacitance voltage (C-V) measurements. The diode having 0.1% Cd doped Zno showed the highest photosensitivity in all the diodes with the photoresponsivity of 3.6 x10− 4. We suggest that the fabricated CdZnO based diodes can be used as photodetector in optic and optoelectronic communications.

Gold nanoparticles supported on mesoporous titania thin films with high loading as a co oxidation catalyst

In the present work, 2.4 nm gold nanoparticles (Au NPs) are uniformly dispersed on mesoporous titania thin films which are structurally tuned by controlling the calcination temperature. The gold content of the catalyst is as high as 27.8 wt %. To our knowledge, such a high loading of Au NPs with good dispersity has not been reported until now. Furthermore, the reaction rate of the gold particles is enhanced by one order of magnitude when supported on mesoporous titania compared to non-porous titania. This significant improvement can be explained by an increase in the diffusivity of the substrate due to the presence of mesopores, the resistance to agglomeration, and improved oxygen activation.