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The optimum etchant composition for precise removal of a thin high-doped silicon gettering layer is determined. It is found that the best-controlled etching is provided by the following composition: HNO3: HF: CH3COOH = 40: 1: 1. This composition etches the entire gettering layer away while preserving the required thickness of the contact layer, which prevents the space-charge region of the p-n junction from emerging at the back surface of the base of a photosensitive element. Thus, this etchant provides an opportunity to reduce the magnitude of dark currents and raise the percentage yield. [ABSTRACT FROM AUTHOR]

Coatings of metal specimens are known to have an impact on hydrogen gettering (hydrogen absorption). The coating can have one or more functions, such as enhancing gettering, preventing gettering and/or preventing oxidation of the metal substrate. It is known that contaminants and surface texture can impact hydrogen gettering/absorption performance, but has not previously been thoroughly explored. This study evaluated the role of different post-plating heat treatments of nickel-plated zircaloy-4 getters (NPGs) and the role of the heat treatments on gettering rates, surface composition and texture. Nickel plating is applied to prevent oxidation of the Zircaloy-4 surface and also enhances gettering. The nickel plating must be heat treated before desirable gettering can occur. Our NPG getters with historically known satisfying performance were pre-heat treated in air followed by activation heat treatment in a vacuum at a higher temperature. In this study, we were interested in finding out if both heat treatment steps were necessary to obtain a desirable gettering performance, or if one step could be omitted. XPS analysis showed that if the nickel surface is not heat treated before bonding the nickel to the zirconium in the activation step, there will be carbon contaminants on the surface, which significantly reduces gettering. We studied the texture of Zircaloy-4 using SEM/EBSD to compare NPGs with both heat treatment steps with NPGs that had no post-plating heat treatment to learn if the degree of cold work could be impacted by the heat treatment steps. We did not observe any differences in texture between them. We measured gettering rates of both pretreated and activated NPGs and NPGs that had been activated without first being pre-heat treated. We found that the NPGs without the first post-plating heating step had up to a seven times slower gettering rate and obtained higher plateau pressures due to the contaminated surface. Thus, the pre-heat treatment in air before activation is necessary to avoid slower gettering rates and higher plateau pressures.

The current paper studies the preparation of a new tannin gel from Acacia nilotica for water purification and waste water remediation. Design of experiments is used for optimizing the tannin gel using tannin extract (Taguchi method) with formaldehyde in the assistance of microwave (TGAN) by the help of iodine number. The feasible combinations were tested in the removal of nickel from simulated and river water. In this study, the effect of adsorbent dosage, pH, and initial metal concentration on Ni (II) biosorption on modified Acacia nilotica tannin gel (TGAN) was investigated. Tannin gel was characterized by SEM, FTIR, XRD, and EDAX. The kinetic data was tested using pseudo-first-order, pseudo-second-order, and intraparticle diffusion model. The results suggested that the pseudo-second-order model (R2 > 0.998) was the best choice among all the kinetic models describing the adsorption behavior of Ni (II) onto TGAN. Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption models were used to represent the equilibrium data. The best interpretation for the experimental data was given by the Langmuir isotherm and the maximum adsorption capacity 250 mg g−1 of Ni (II) was obtained at pH 5.04 at 296 K. Adsorption of Ni (II) onto TGAN is confirmed qualitatively by the use of atomic absorption spectroscopy. The BOD and COD values are considerably reduced after adsorption. [ABSTRACT FROM AUTHOR]

This paper describes a study to understand the impact of heat treatment on the crystal Silicon (c-Si) with developed surface by Aluminum /Porous silicon (Al/PS) and evaluating their influence on the solar cell performance. In fact, the heat treatment of silicon surfaces with PS/Al is an effective means of structural and electrical adjustment and performance improvement of c-Si solar cells. The new process could be accomplished by a two-step annealing in order to benefit from both the high and low temperature processes. The advantages of such a new getter in comparison with traditional getter were demonstrated in various devices. We can estimate that the resistivity using the standard Van Der Pauw, and LBIC measurements have been performed to determine the diffusion length. The resistivity of crystalline silicon decreased when the porous layer was removed at about a depth around 70 μm. As a result, we found amelioration in the I – V characteristics and an enhancement of minority carrier lifetime. It has been shown that this simple method leads to improve the charge carrier collection and the electrical properties of c-Si based solar cells. [ABSTRACT FROM AUTHOR]

The laser gettering of silicon wafers is experimentally investigated. The typical gettering parameters are considered. The surfaces of laser-treated silicon wafers are investigated by microscopy. When studying the effect of laser radiation on silicon wafers during gettering, a group of factors determining the conditions of interaction between the laser beam and silicon-wafer surface and affecting the final result of treatment are selected. The main factors determining the gettering efficiency are revealed. Limitations on the desired value of the getter-layer capacity on surfaces with insufficiently high cleanness (for example, ground or matte) are established. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have been targeted as solid state sorbents for postcombustion carbon dioxide capture due, in part, to the enormous tunability of their structures through the incorporation of different functional sites. The isosteric heat of adsorption (Qst) provides one measure of the interaction of a solid sorbent with guest molecules, and has a bearing on the low pressure (<1 bar) CO2 uptake, selectivity and regenerability of a material. It is a key factor in the design of adsorbents for gas separation; however, it is sometimes overlooked in the evaluation of MOFs for CO2 capture. This highlight article draws together the impact of various functional sites on the CO2 heat of adsorption, and examines the interplay between functional sites and other factors such as competing water adsorption that influence a material's suitability for CO2 capture from industrial streams. [ABSTRACT FROM AUTHOR]

Research into lithium as a plasma facing component material has illustrated its ability to engender low recycling operation at the plasma edge leading to higher energy confinement times. Introducing lithium into a practical fusion device would almost certainly require the lithium to be flowing to maintain a clean lithium surface for gettering. Several conceptual designs have been proposed, like the LiMIT concept of UIUC (Ruzic, 2011). Critical to the implementation of these devices is understanding the interactions of liquid lithium with various surfaces. For a device that relies on thermoelectric magnetohydrodynamic drive, such as the LiMIT concept, two of the critical interactions are the wetting of materials by lithium, which may be characterized by the contact angle between the lithium and the surface, and the relative thermopower between lithium and potential substrate materials. Experiments have been performed into the contact angle of liquid lithium droplets with various surfaces, as well as methods to decrease the contact angle of lithium with a given surface. The contact angle, as well as its dependence on temperature was measured. For example, at 200 °C, tungsten registers a contact angle of 130°, whereas above its wetting temperature of 350 °C, the contact angle is less than 80°. Glow discharge cleaning of the target surface as well as evaporation of a thin layer of liquid lithium onto the surface prior to performing wetting measurements were both found to decrease the wetting temperature. [ABSTRACT FROM AUTHOR]

Novel Fe3O4@mTiO2@GO microspheres for the fast removal of Cr(vi) were synthesized by immobilizing a mesoporous TiO2 shell on the surface of magnetic Fe3O4 nanoparticles prior to binding with GO. The characterization results from FTIR, SEM, VSM and XRD showed that Fe3O4@mTiO2@GO was successfully prepared with a large surface area and good magnetic responsiveness. It was shown that the sorption of the microspheres for Cr(vi) was strongly dependent on pH value and contact time. As Cr-removal adsorbents, the maximum Cr-removal capability of microspheres was 117.94 mg g−1. The equilibrium adsorptions were well-described by the Freundlich isotherm mode and its kinetics followed pseudo-second-order rate equation. Moreover, the Fe3O4@mTiO2@GO microspheres could be regenerated and used repeatedly by simple treatment without obvious structure and performance degradation. These results demonstrated the potential applications of Fe3O4@mTiO2@GO microspheres in the efficient Cr-removal from wastewater and purification of polluted water. [ABSTRACT FROM AUTHOR]

The concept of this study is based on self-assembled formation of voids in strained Si/SiGe heterostructures, and formation of nano-shells and nano-particles of gold through a gettering process. The gettering of vacuum deposited gold to the voids was studied using Rutherford backscattering and transmission electron microscopy. A very well defined layer of voids was formed in the strained SiGe layer at a depth of 0.5 µm as a result of helium implantation and thermal annealing. Due to strain enhanced vacancy accumulation, the voids nucleate and grow exclusively in the SiGe layer. The voids then getter large amount of Au which cover the inner walls of the voids at low temperature or precipitates into void-located nano-crystals at a temperature of 850 °C. Effects connected to structural transformations in the Si/SiGe layers during self-assembling of nano-voids and metallic dots, the optical properties of the layers, and the resulting effects of nanostructures on the spectral dependence of the photocurrent in the Si/SiGe structures are reported. [ABSTRACT FROM AUTHOR]

We studied the influence of copper (Cu) on the performances of conventional photovoltaic (PV) solar cells by growing two multicrystalline (mc) boron-doped silicon (Si) ingots from ultra-pure feedstocks, one of these feedstocks being deliberately contaminated with 90 ppm wt of Cu. Industrial-like solar cells were fabricated and the associated external gettering and hydrogenation effects were studied. An originality of our approach consisted in evaluating the forward but also reverse current-voltage (I-V) characteristics of the fabricated cells. Furthermore we assessed the stability under illumination of the PV parameters as Cu is known to be responsible for light-induced degradations (LID) of the carrier lifetime. On the one hand we unexpectedly showed that the PV conversion efficiency (η) was not affected by the initially large Cu concentrations. We demonstrated that it was due to the complementary actions of the external gettering effect developed by the phosphorus-diffusion and the bulk hydrogenation. The Cu-addition slightly enhanced the pn junction hard breakdown, however the extracted junction breakdown voltages fulfilled the common industrial requirements for this parameter. On the other hand we highlighted significant decreases under illumination of the PV performances for the Cu-contaminated solar cells fabricated from wafers coming from the upper part of the ingot (i.e., samples with the highest Cu concentration). These decreases could be explained by the previously proposed mechanisms in the literature, which argue that the excess charge carriers could reduce the electrostatic repulsion between interstitial Cu ions and Cu precipitates, this effect enhancing the Cu precipitation. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Low energy As or Sb ion implantation followed by furnace annealing was used to create ultra shallow junctions. It was found that a significant amount of oxygen was redistributed from the Si bulk to the As implanted layer leading even to an increase of the screening oxide film thickness. Using a marker layer created by implantation of 18O ions, it was confirmed that a large number of interstitial oxygen atoms are transferred from the bulk of the Si wafer to the wafer surface during implanted As activation annealing. Estimation of the O diffusivity in Si during the 950 °C activation anneal, yields a value of about 10-10 cm2 /s which is more than an order of magnitude larger than the literature value which is close to 7 × 10-12 cm2/s. In the case of Sb implantation, the oxygen gettering effect is much reduced. This difference in oxygen behavior can be attributed to the influence of mechanical stress in the near surface highly doped layer. The configuration of the mechanical stress field is different for the cases of As and Sb implantation, with tensile stress dominating for the latter. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

In this study, the authors developed an approach for accurately quantifying the helium content in a gas mixture also containing hydrogen and methane using commercially available getters. The authors performed a systematic study to examine how both H2 and CH4 can be removed simultaneously from the mixture using two SAES St 172® getters operating at different temperatures. The remaining He within the gas mixture can then be measured directly using a capacitance manometer. The optimum combination involved operating one getter at 650 °C to decompose the methane, and the second at 110 °C to remove the hydrogen. This approach eliminated the need to reactivate the getters between measurements, thereby enabling multiple measurements to be made within a short time interval, with accuracy better than 1%. The authors anticipate that such an approach will be particularly useful for quantifying the He-3 in mixtures that include tritium, tritiated methane, and helium-3. The presence of tritiated methane, generated by tritium activity, often complicates such measurements. [ABSTRACT FROM AUTHOR]

In this work we investigate the effect of the bulk metal contamination level in cast silicon on the electrical performance of PERC (passivated emitter and rear cell) solar cells [1] . The bulk contamination is varied in two different ways. In the first approach, cast silicon crystallized with high purity silicon feedstock and reduced metal contamination from crucible and coating is used. Second, an extended gettering step is introduced in the PERC process flow. The interstitial iron concentration is taken as a measure of the bulk metal contamination of the investigated cells. Both the higher purity cast silicon and the gettering step significantly lower the interstitial iron concentration in the resulting PERC cells. This clear positive effect is also mirrored in solar cell parameters such as the open circuit voltage U OC . In this experiment, the impact of gettering is larger than the effect which is reached by reducing the bulk metal concentration during the crystallization process. Device simulations show that most of the difference in U OC can be explained by the different interstitial iron levels while other recombination active defects might also be present. [ABSTRACT FROM AUTHOR]

The role of iron in crystalline silicon solar cells has been extensively investigated, yet the interaction mechanisms with structural defects have not been fully understood. In this work we have investigated a multicrystalline silicon ingot made in a small scale (1.5 kg) vertical gradient freeze (VGF) furnace with the addition of 50 ppma Fe in the polysilicon feedstock. The minority carrier lifetime was qualitatively measured by photoluminescence (PL). Grain morphology and -orientation were determined by electron backscatter diffraction (EBSD). The comparison between the PL and EBSD maps shows high lifetime areas near the grain boundaries, which is explained by an internal gettering mechanism. Furthermore, it is evident that Fe segregates slightly at coincidence site lattice (CSL) boundaries – especially at Σ3, while it segregates heavily at random grain boundaries. These results indicate the dependence of Fe segregation towards defect on grain boundary character. A method to qualitatively and quantitatively identify the segregation profiles and depleted region thickness is developed by image analysis. [ABSTRACT FROM AUTHOR]

Magnetic quaternary chitosan salt CS/EPTAC/Fe3O4 was used for the removal of acid red 1 (AR1), xylenol orange (XO) and alizarin red (AR) in single, binary and ternary systems. In the single system, the maximal adsorption capacity was 781.55 for AR1, 537.40 for XO and 992.61 mg g-1 for AR at pH 3.0 and 25 °C. The adsorption kinetics of the three dyes followed the pseudo-second-order model. In the multicomponent system, preferential adsorption was observed for AR at low adsorbent quantities due to the small size of the molecule. When the adsorbent amount was greater, AR1 was adsorbed first because of the greater number of sulfonic acid roots. In the entire adsorption process, XO always adsorbed most slowly. [ABSTRACT FROM AUTHOR]

This study involved developing a low-power and high-mobility metal–oxide thin-film transistor that incorporated a bilayer IGZO/IGZO:Ti semiconductor material. Compared with control metal–oxide TFTs, the bilayer IGZO TFT through thickness modulation of IGZO:Ti can reach the smallest subthreshold swing (85 mV/decade) and the highest field effect mobility (49 cm2/Vs) at a drive voltage of <3 V. This performance level improvement can be attributed to the gettering effect caused by the IGZO:Ti capping layer and its dual advantages, which enhance device mobility and improve gate swing. [ABSTRACT FROM PUBLISHER]

The adhesion of powder particles on solid surfaces is influenced by many parameters. Among these influence factors the van-der-Waals-forces and the humidity of the surrounding atmosphere play a dominant role. Since current models often neglect important parameters, in this paper different possibilities to calculate particle adhesion forces are presented. The calculated values allow the interpretation of adhesion force distribution and the assignment of adhesion forces to certain mechanisms. [ABSTRACT FROM AUTHOR]

Ultra-shallow junctions were formed by low-energy As ion implantation followed by furnace annealing. It was found that a significant amount of oxygen is redistributed from the silicon bulk to the As-implanted region. Using a marker layer created by implantation of 18O isotope, it is confirmed that a large number of interstitial oxygen atoms are transferred from the bulk of Si wafer to the surface during dopant activation annealing, which leads to an increase of the surface oxide thickness. Estimation of the oxygen diffusivity in silicon during the 950��C anneal, yields a value close to 1�נ10−10�cm2�s−1�which is more than an order of magnitude larger than the literature value which is close to 7�נ10−12�cm2�s−1. [ABSTRACT FROM AUTHOR]

External phosphorous diffusion gettering were applied using homogenous and extended schemes on multicrystalline silicon (Mc-Si) wafers obtained from solar grade (SOG) silicon feedstock by the heat exchange method (HEM) growth technique. X-ray fluorescence (XRF) characterization shows the presence of transition metals like Chromium (Cr), manganese (Mn) and iron (Fe) in the analyzed as-cut Mc-Si substrates with a predominance of Mn and Fe elements. Before and after gettering process, we have observed that the Cr atoms concentration drop from 4.1015 at.cm-3 in the as-cut Mc-Si samples to 2.5 1015 at.cm-3 with homogeneous gettering and to 3.1014 at.cm-3 in the wafer undergoes extended gettering. The quasi-steady-state photo conductance (QSSPC) technique is used to characterize the minority charge carrier’s lifetime tn before and after gettering process. It was found that the response of Mc-Si wafers is better (form point of view of lifetime improvement) to the extended process but in some regions it is less effective and the homogenous process give the best amelioration due probably to the spatial distribution of crystalline defects and metallic precipitates densities. With tn initial values before gettering in the range of 2.5-8 usec we have measured lifetime values in the range of 15 to 37 usec with extended process and from 10 to 30 µsec with the homogenous one which ensure cell efficiencies in the range of 15 to 16%.