K. Siraj

Angular distribution and forward peaking of laser produced plasma ions

This paper represents the results of a study of angular distribution of laser produced ions ~LPI! of Al, Cu, and Ag. The angulardistributionisstudiedbyCR-39 ~SSNTD!andionassistedsputteringexperiments.AQ-SwitchedNd:YAGlaser ~1.064 mm,1.1MW!with10mJpulsedenergywasusedtoproducetheAgions,whichweredetectedbyCR-39detector mounted at17.58 ,0 8, 17.58 ,3 08 ,6 08, and 908 from the normal to the target placed at a distance of 9 cm from the target. Etched CR-39 detectors then observed under the Motic DMB Series optical microscope. A bunch of ions was detected alongthenormaloftargetduetoselfgeneratedcollimationofions.ThisistermedasForwardPeakingofLaserProduced Ions. Similar results were also observed from sputtering of polished Al substrate by laser produced ions of Cu and Sputtering of polished Cu substrate by laser produced ions ofAl. The surface morphology of the ion irradiated samples were observed under the Scanning Electron microscope ~SEM! S 300 Hi-tech. Formation of a circular damage on the surface of the substrates by irradiation conforms the ions collimation along the normal or Forward Peaking of ions.

Significance enhancement in the conductivity of core shell nanocomposite electrolytes

Today, there is great demand of electrolytes with high ionic conductivities at low operating temperatures for solid-oxide fuel cells. Therefore, a co-doped technique was used to synthesize a highly ionically conductive two phase nanocomposite electrolyte Sr/Sm–ceria–carbonate by a co-precipitation method. A significant increase in conductivity was measured in this co-doped Sr/Sm–ceria–carbonate electrolyte at 550 °C as compared to the more commonly studied samarium doped ceria. The fuel cell power density was 900 mW cm−2 at low temperature (400–580 °C). The composite electrolyte was found to have homogenous morphology with a core–shell structure using SEM and TEM. The two phase core–shell structure was confirmed using XRD analysis. The crystallite size was found to be 30–60 nm and is in good agreement with the SEM analysis. The thermal analysis was determined with DSC. The enhancement in conductivity is due to two effects; co-doping of Sr in samarium doped ceria and its composite with carbonate which is responsible for the core–shell structure. This co-doped approach with the second phase gives promise in addressing the challenge to lower the operating temperature of solid oxide fuel cells (SOFC).

High performance of SDC and GDC core shell type composite electrolytes using methane as a fuel for low temperature SOFC

Nanocomposites Samarium doped Ceria (SDC), Gadolinium doped Ceria (GDC), core shell SDC amorphous Na2CO3 (SDCC) and GDC amorphous Na2CO3 (GDCC) were synthesized using co-precipitation method and then compared to obtain better solid oxide electrolytes materials for low temperature Solid Oxide Fuel Cell (SOFCs). The comparison is done in terms of structure, crystallanity, thermal stability, conductivity and cell performance. In present work, XRD analysis confirmed proper doping of Sm and Gd in both single phase (SDC, GDC) and dual phase core shell (SDCC, GDCC) electrolyte materials. EDX analysis validated the presence of Sm and Gd in both single and dual phase electrolyte materials; also confirming the presence of amorphous Na2CO3 in SDCC and GDCC. From TGA analysis a steep weight loss is observed in case of SDCC and GDCC when temperature rises above 725 °C while SDC and GDC do not show any loss. The ionic conductivity and cell performance of single phase SDC and GDC nanocomposite were compared with core sh...

Laser-produced copper ion energy spectrum employing Thomson scattering technique

Investigations were performed on laser-assisted ion emission when a copper target was irradiated with a Nd:YAG laser (1.064 μm 10 mJ and 1.1 MW). Charge states present in the ion core emitted from plasma were determined employing Faraday cup arrangement using a four-channel 500 MHz Digital Storage Oscilloscope YOKOGAWA DL 1740. The Thomson parabola scattering (TPS) technique was used to measure the energy of ions emitted from plasma. Singly charged positive ions were found to be in excessive amount. For the energy analysis, the ion beam was collimated using a pinhole arrangement. The collimated beam was then made to pass through a uniform magnetic field of 0.4 T. A solid-state nuclear track detector PM-355 was used to register the ion tracks. The energy of ions, found to be in the range of 9–50 keV. The ion energy spectra d2N/dEdΩ show a decreasing trend with increasing ion energy. The empirical relation dN/dE ∞ E−n fits well with the experimental data at higher values of energy, i.e., greater than 20 keV.

Laser shots impact on geometry of crater evolution at copper surface

Fine polished 4N (99.99%) pure copper samples are irradiated in ambient air using Q-Switched Nd:YAG Laser (10 mJ, 9–12 ns, 1064 nm). The laser energy density and spot size at tight focus are 3×1011 W/cm2 and ∼12 μm, respectively. The laser-produced crater is analyzed considering its dimensional changes with the increase in laser shots employing optical microscopy. The width of the crater (along horizontal) increases, thereby exhibiting its exponential trend. The length along the vertical and the depth of the crater both increase exponentially. The heat-affected zone expands exponentially as well. Hydrodynamics and exfoliation are the two main dominant observed ablation mechanisms.

Theoretical and Experimental Comparison of Splashing in Deposition of Copper and Graphite Thin Films by PLD

This paper represents the comparison results of experimental observations and theoretical calculations for splashing in deposition of Copper and Graphite thin films. These films were deposited by Pulsed Laser Deposition (PLD) technique. A Q-Switched Nd:YAG nano-second laser with 1.1 MW power. Thin films and Target surface morphology were studied under the Scanning Electron Microscope (SEM) Splashing was observed only in the copper thin films but not in graphite thin film. Theoretical models also shows the splashing only in copper, not in graphite at 1012 W/cm2 intensity of laser radiation. Because skin depth for copper (of the order of nm) smaller than that of graphite (of the order of μm) for IR radiation. Skin depth is directly related with splashing threshold intensity. Splashing produced that nonuniformity in thin films which reduced application of thin films especially in nano-electronics and smart materials.

Dopant-induced modifications in structural and optical properties of ZnO thin films prepared by PLD

The objective of the present work is to study the effect of yttrium doping concentration on the microstructure and optical behavior of ZnO thin films, deposited by pulsed laser deposition on silicon (001) substrates. The microstructural analysis of doped ZnO thin films shows columnar growth of the ZnO (002) plane under tensile stress, confirmed by Raman shifts of the E2 (high) mode. The optical properties are investigated by using a spectroscopic ellipsometer. Undoped and yttrium-doped ZnO films show high transparency in the visible region, and the estimated optical band gap energy is randomly shifted in the range 2.93–3.1 eV by increasing the yttrium doping level. Yttrium doping in ZnO is limited, which means that at doping concentrations higher than 3 wt.% of yttrium, the structural and optical properties show a shift towards those of undoped ZnO.

Surface-pattern geometry, topography, and chemical modifications during KrF excimer laser micro-drilling of p-type Si (111) wafers in ambient environment of HCl fumes in air

Eight mirror-like polished p-type Si (111) wafers were irradiated with 100, 200, 300, 400, 800, 1200, 1600, and 2000 KrF excimer laser pulses in ambient environment of HCl fumes in air. The laser parameters were: wavelength = 248 nm, pulse width = 20 ns, pulse energy = 20 mJ, and repetition rate = 20 Hz. For each set of laser pulses, characterization of the rectangular etched patterns formed on target surface was done by optical/scanning electron microscopy, XRD, and EDX techniques. The average etched depth increased with the increase in number of laser pulses from 100 to 2000 in accord with Sigmoidal (Boltzmann) function, whereas the average etch rate followed an exponential decay with the increase in number of laser pulses. However, the etched area, maximum etched depth, and maximum etch rate were found to increase linearly with the number of laser pulses, but the rate of increase was faster for 100–400 laser pulses (region I) than that for 800–2000 laser pulses (region II). The elemental composition for each etched-pattern determined by EDX shows that both O and Cl contents increase progressively with the increase in the number of laser shots in region I. However, in region II both O and Cl contents attain saturation values of about 39.33 wt.% and 0.14 wt.%, respectively. Perforation of Si wafers was achieved on irradiation with 1200–2000 laser pulses. XRD analysis confirmed the formation of SiO2, SiCl2 and SiCl4 phases in Si (111) wafers due to chemical reaction of silicon with both HCl fumes and oxygen in air.