Evaporated Thin Films of CdS and CdTe: Optimization for Photovoltaic Applications

Thin films of cadmium sulphide and cadmium telluride have been prepared by thermal evaporation under various conditions of deposition. These films have been characterized optically. electrically and for structure determination. The results of these characterizations along with the initial results of all thin film CdS/CdTe solar cells are presented in this paper.

Layer resolved magnetization reversal study in SmCo_5 /Fe nanocomposite bilayers

A hard/soft SmCo5/ Fe nanocomposite magnetic bilayer system is fabricated on x-ray transparent 100-200 nm thin SiaN4 films by magnetron sputtering. The microscopic magnetic domain pattern and its behaviours during magnetization reversal in the hard and the soft magnetic phases are studied separately by element specific magnetic soft x-ray microscopy at a spatial resolution of better than 25 Nm. We observe that the domain patterns for the soft and hard phases show coherent behaviours in varying magnetic fields. We derive local M（H） curves from the images of Fe and SmCo5 separately and find the switches for hard and soft phases to be the same.

Effect of Reaction Temperature and Time on the Structural Properties of Cu(In,Ga)Se_2 Thin Films Deposited by Sequential Elemental Layer Technique

Thin films of copper indium gallium selenide Cu（In,Ga）Se2 （CIGS） were prepared by sequential elemental layer deposition in vacuum at room temperature. The as-deposited films were heated in vacuum for compound formation, and were studied at temperature as high as 1250℃ for the first time. These films were concurrently studied for their structural properties by X-ray diffraction （XRD） technique. The XRD analyses include phase transition studies, grain size variation and microstrain measurements with the reaction temperature and time.It has been observed that there are three distinct regions of variation in all these parameters. These regions belong to three temperature regimes： 〈450℃, 450-950℃, and 〉950℃. It is also seen that the compound formation starts at 250℃, with ternary phases appearing at 350℃ or above. Whereas, there is another phase shift at 950℃ without any preference to the quaternary compound.

Cutting of nonmetallic materials using Nd:YAG laser beam

This study deals with Nd：YAG laser cutting nonmetallic materials, which is one of the most important and popular industrial applications of laser. The main theme is to evaluate the effects of Nd：YAG laser beam power besides work piece scanning speed. For approximate cutting depth, a theoretical study is conducted in terms of material property and cutting speed. Results show a nonlinear relation between the cutting depth and input energy. There is no significant effect of speed on cutting depth with the speed being larger than 30 mm/s. An extra energy is utilized in the deep cutting. It is inferred that as the laser power increases, cutting depth increases. The experimental outcomes are in good agreement with theoretical results. This analysis will provide a guideline for laser-based industry to select a suitable laser for cutting, scribing, trimming, engraving, and marking nonmetallic materials.

Optical Investigation of Sm^(3+) Doped Zinc-Lead-Phosphate Glass

Samarium doped lead-zinc-phosphate glasses having composition(60-x)P_(2)O_(5)-20PbO-20ZnO-xSm_(2)O_(3) where x=0,0.5,1.0,3.0mol%were prepared by using the melt quenching technique.The Archimedes method was used to measure their densities,which are used to calculate the molar volumes.The values of densities lie in the range 3.698–4.090 gm/cm^(3) whereas those of molar volume lie in the range of 37.24–40.00 cm^(-3).UV-vis-NIR absorption spectroscopy in the wavelength range 200–2000 nm was carried out.Absorption spectra consist of seven absorption peaks corresponding to the transitions from the 6H5/2 ground state to various excited energy levels.The energy band gap measured from the optical absorbance is found to be in the range of 3.88–4.43 eV and 3.68–4.33 eV for direct and indirect transitions,respectively.In addition,the photoluminescence spectrum shows four prominent emission bands centered at 560,597,642 and 700 nm corresponding to the 4G5/2–6HJ(J=5/2,7/2,9/2,11/2)transitions respectively and the intensity of all the bands are enhanced as the concentration of Sm3+ions increases.

A Study of Supersaturation Spectra of Deposition Ice Nuclei

Ice nuclei-supersaturation spectra in the form of a Power Law ( Ni=RSir; B and y are empirical constants) have been expressed since 1973 when the curve was first introduced independentally by Gagin and Huffman. Experiments performed with a thermal gradient diffusion chamber in order to investigate the validity of the power curve. The results show that a linear curve fit to the data is as good as the power curve. The linear curve has the coefficients of correlation between 0.75 and 0.93 whereas the power curve fit to the same data has the coefficients between 0.82 and 0.93. The data reported by other workers, Zamurs and Jiusto and Zamurs et al., exhibit the same trend.

Effect of Temperature on Structural and Magnetic Properties of Laser Ablated Iron Oxide Deposited on Si（100）

我们用搏动的激光免职在不同温度在 Si (100 ) 底层上制作 Fe3O4 薄电影，并且学习退火和免职温度在上的效果结构并且 Fe3O4 薄电影的磁性。随后，这些电影被 X 光衍射(XRD ) 描绘，扫描电子显微镜学(SEM ) 和颤动的样品 magnetometery (VSM ) 。这些电影的 XRD 结果证实 Fe3O4 阶段和表演房间温度强磁性的存在，与 VSM 观察了。当时，我们为很高的 854 emu/cm3 的提高的磁化表明优化免职和退火的条件与体积样品相比。

Fabrication and Characterization of SmCo5/Fe65Co35 and SmCo5/Fe Composite Spring Exchange Magnets

SmCo5/Fe65Co35 和 SmCo5/Fe 春天交换磁铁被制作由做磁控管在 MgO 底层和 100-nm-thick Si3N4 膜上劈啪作响分别地。劈啪作响的房间的基础压力低于 10 被保留(-7) Torr，和 Ar 压力是 3 到 8mTorr。样品被 X 光衍射计，一个超导的量干扰磁强计，和高分辨率描绘磁性的软 X 光显微镜学。我们获得联合的完全的交换和合成磁铁的单个阶段行为。(BH )( 最大) 完成的价值是 28.8 MGOe。

PREPARATION OF THERMALLY EVAPORATED CdTe THIN FILMS

Thin films of cadmium telluride were prepared by evaporating cadmium telluride powder in a vacuum of less than 10^(-4) Torr.The substrate temperature was varied systematically from room temperature to 300℃.The results of optical and structural characterizations have revealed that the films posses a high value of absorption coefficient with a bandgap value m the range 1.475-1.769eV,and that the films are of cubic structure with a preferred orientation along(111)plane.Four probe measurements have shown that resistivity of these films is affected by the change in substrate temperature,with the lowest value(12.6 Ω·cm)being at 200℃.

Preparation and Properties of Evaporated CdTe and All Thin Film CdTe/CdS Solar Cells

Cadmium telluride thin films were prepared by vacuum evaporation of CdTe powder in an attempt to fabricate all thin film solar cells of the type CdTe/CdS.Characterization of CdTe has shown it to have a band gap of 1.522eV and a resistivity of 22Ω-cm.As prepared,solar cells exhibited low values of output parameters.Given quantity of copper was then deposited on top of the CdTe/CdS solar cells and the whole system was annealed at 350℃.This copper doping changed the output parameters favorably with a maximum efficiency of 1.9%.

Plasmon-Enhanced Upconversion Fluorescence in Er^(3+):Ag Phosphate Glass:the Effect of Heat Treatment

The melt quenching method is used to prepare erbium-doped silver nanoparticle(NP)embedded phosphate glass.The effect of annealing on the glass on the formation of silver NPs produced by the reduction of silver(Ag^(+)→Ag^(o))is studied.The glass samples are characterized by x-ray diffraction,UV-vis-NIR absorption,photoluminescence spectroscopy and transmission electron microscopy(TEM)imaging.The absorption spectra reveal not only the peaks due to Er^(3+)ions,but also the surface plasmon resonance band of silver NPs located around~442 nm.The TEM imaging shows the homogeneous distribution of silver NPs of almost spherical shape with an average diameter of~5 nm.Upconversion luminescence spectra show two major emissions at 550 and 638 nm,originating from the 4S_(3/2)and 4F_(9/2)energy levels of the Er^(3+)ions,respectively.The enhancement in the luminescence intensity of both the green and red bands is found to be due to the effective local field of the silver NPs as well as the energy transfer from the nanoclusters,comprised of centers with silver ions bound to silver atoms in dimers or trimers to Er^(3+)ions,whereas quenching occurred due to the energy transfer from erbium ions to silver NPs(Er^(^(3^(+)))→Ag^(o)).

Origin of Ferromagnetism in Al and Ni Co-doped ZnO Based DMS Materials

Zn0.95Ni0.05O and Zn0.90Ni0.05Al0.05O compositions of nanocrystallites are synthesised using the well recognised auto-combustion technique.The x-ray diffraction patterns demonstrate the phase pure characteristic wurtzite-type crystal structure with space group P63mc in both the compositions.The elemental incorporation of Ni and Al contents into the ZnO structure is confirmed by energy dispersive x-ray analysis.The micrographs of scanning electron microscopy show an approximate ordered morphology.The electrical resistivity is observed to decrease with the rising temperature,depicting the characteristic semiconductor behaviour of the samples.The lower values of resistivity and ferromagnetic interactions in the Al-doped sample correspond to an increase of carrier's density.It is observed that the carrier mediated mechanism is mainly responsible for ferromagnetism in ZnO-based diluted magnetic semiconductors.

A Study of Suspended Particulate Matter in Lahore (Pakistan)

The results obtained from an investigation of suspended particulate matter in the metropolitan city of Lahore (Pakistan) are reported and analysed in this paper. X-ray diffraction studies of the airborne matter collected from various urban and suburban sites show that non-clay minerals such as quartz, calcite and albite are contained in most of the samples in almost comparable amounts. Chemical analysis of some samples was carried out for complementing the x-ray diffraction data. The amount of quartz in the samples of dusty areas was found to be an order of magnitude more than in the samples of relatively cleaner areas. As the dust particles of these compounds are poor substrate for promoting nucleation of ice in the atmospheric clouds, they are liable to stay steadily in the atmosphere as pollutants.A comparison of the results of the airborne particulates and the soil samples collected from various sites show that the sources of quartz, calcite and albite in the airborne matter are both local and remote.

Quantification of Phases in Lahore (Pakistan) Airborne Particulates by Matrix-Flushing Method

The mass concentrations of eighteen airborne samples collected from Lahore (Pakistan) are found in the range from 595 to 3027μg/m3with average value of 1130 μg/m3. Most of these values are normal and as reported in the literature for other parts of the world. The major phases identified in the samples by the X-ray powder diffraction technique are Albite (Anorthite), Calcite, Clinochlore (Chlorite), Gypsum, Illite, Quartz and Talc which have also been reported by other researchers to be present in the airborne particulates of other world locations. The average weight percentages of the phases (minerals) in the samples are respectively 15.5, 10.6, 23.7, 2.4, 19.1, 20.2, and 8.5. Some of the elements (e.g., boron, cadmium, lithium, manganese, titanium, and zinc) quantified in two samples determined using a spark-source mass spectrometer appear also to derive their origin from man-made activities. However no compound synthesized in the atmosphere is detected by the X-ray diffraction method.

Magnetic Behaviour of Sm2Co7/Fe/Sm2 Co7, Nanocomposite Trilayers with Cr and Ti Additions

Trilayered Sm2Co7/Fe/Sm2Co7 spring exchange magnets are fabricated by dc magnetron sputtering on MgO substrates. Very thin layers （0.3-0.7 nm） of Cr and Ti are added at the interfaces of the two magnetic phases. The thickness of StucCo7 is kept at 20nm and Fe at 6nm while the thickness of Cr and Ti are varied as 0.3, 0.5, and 0.7nm. The base pressure of sputtering chamber is kept below 10^-7 Torr and Ar pressure at 3-8m Torr. The samples are characterized by x-ray diffraction （XRD） and SQUID magnetometer. We report improvement in exchange coupling of nonacomposite magnets by addition of thin layers of Cr at interfaces.

Enhancement in energy product in Sm-Co/Fe exchange coupled magnetic layers with molybdenum interlayers

Trilayers of Sm-Co/Mo/Fe were deposited by DC and RF magnetron sputtering on Si(100) substrate at 650 °C.Effect of very thin Mo interlayers on energy product of magnetic layers was studied.All the samples showed strong exchange coupling and single phase behavior.With increasing Mo interlayer thickness,we observed oscillating behavior of saturation magnetization and energy product.The rise in energy product was observed as 22% for 0.3 nm Mo interlayer as compared to sample without Mo interlayer.