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Presence of a native oxide interlayer degrades seriously the contact resistivity ($\rho _{{\text {c}}}$) of co-deposited TiSi (CD-TiSi) on Si:P. The oxide cannot be scavenged by the CD-TSi due to its low solid solubility of O. We tackle the problem by capping the CD-TiSi with an O gettering cap. Utilizing a Ti cap and two-step post-metal rapid thermal anneal, we reduce the $\rho _{{\text {c}}}$ of the CD-TiSi on ${2}\times {10}^{{21}}$ cm $^{-{3}}$ doped Si:P by ${\sim }{3}$ times, down to ${\sim }{2} \times {10}^{-{9}}\,\,\Omega \cdot \text {cm}^{{2}}$. We also demonstrate efficiency of a La cap to scavenge the oxide. [ABSTRACT FROM AUTHOR]

We developed a high-gettering-capability silicon wafer for advanced CMOS image sensors using hydrocarbon molecular ion implantation. We found that this novel silicon wafer has an extremely high gettering capability for metal, oxygen, and hydrogen impurities during the CMOS device fabrication process. We also found that the white spot defect density of a hydrocarbon-molecular-ion-implanted CMOS image sensor was substantially lower than that of a CMOS image sensor without hydrocarbon molecular ion implantation. This indicates that the novel silicon wafer helped improve device performance parameters such as white spot defect density and dark current. We believe that this wafer will be beneficial in the design of silicon wafers for advanced CMOS image sensor fabrication. [ABSTRACT FROM AUTHOR]

For the first time, comprehensive comparative investigations of ultraviolet photodetectors with Cr Schottky barriers formed on 4H-SiC epitaxial layers are carried out by the X-ray and optical methods before and after irradiation with 15-MeV protons with fluences in the range of (1–4) × 1012 cm–2. When increasing the fluence of proton irradiation, the formation of localized regions with negative deformation is observed along with the unperturbed silicon-carbide matrix. Agreement between the X-ray and optical studies is obtained, which makes it possible to explain the features of the spectral changes in the photosensitivity of detectors in the range of 200–400 nm with an increase in the fluence of proton irradiation. The ultraviolet Cr/4H-SiC photodetectors withstand irradiation by 15-MeV protons with a fluence of 4 × 1012 cm–2 virtually without any changes in the photosensitivity due to the gettering of simple defects by cluster and amorphous formations, which lead to partial structural improvement of the irradiated material. [ABSTRACT FROM AUTHOR]

Abstract In this study, we investigated the effect of titanium addition on microstructure and mechanical properties in Mo-Si-B alloys. The Mo-Ti-Si-B alloy (Mo-3.9Ti-3Si-1B, wt%), which has α-Mo, Mo 3 Si, Mo 5 SiB 2 and TiO 2 phases , was fabricated by a powder metallurgy (PM) method. The starting materials were pulverized by using a high-energy ball milling and the resultant powder was subjected to a reduction process followed by cold isostatic pressing (CIP) compaction and pressureless sintering. In the microstructure, intermetallic compound phases were uniformly distributed in the α-Mo matrix. Some titanium atoms solved into the α-Mo matrix and the others formed a TiO 2 phase caused by reaction with oxygen at the grain boundary. Fracture toughness of the Mo-Ti-Si-B sintered body was recorded as 10.42 MPa·m1/2, which is lower than that of the Mo-Si-B sintered body without addition of titanium. In the Mo-Ti-Si-B sintered body, the fracture mode is similar to the Mo-Si-B sintered body where intergranular fracture through the Mo grain boundary and transgranular fracture cross the intermetallic compound phase. The decrease of fracture toughness is due to the relatively large TiO 2 at the grain boundary, promoting intergranular fracture. Highlights • The effect of titanium addition in Mo-Si-B alloys was investigated. • Quaternary Mo-Ti-Si-B sintered bodies were fabricated by novel powder metallurgical method. • In microstructure and XRD analysis, some titanium reacted with oxygen and the others were solved in the α-Mo matrix. • Fracture toughness of Mo-Ti-Si-B alloys decreased due to grain boundary weakening caused by existence TiO 2 particle. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the influence of an annealing process at 500 °C for 30 min. after emitter diffusion of multi-crystalline solar cells was investigated. Neighboring sister wafers from a silicon ingot were processed using light doped emitter (LDE) and low temperature annealing (LTA). Emitter profiles measured by Electrochemical Capacitance Voltage (ECV) showed that there is no obvious difference between LDE and LTA due to the lower annealing temperature. The lifetime and iron concentration measurement indicated that the gettering of LTA diffusion is much better than LDE. Therefore, the solar cell efficiency of LTA was up to 19.01%, which is 0.28%abs higher than LDE due to the higher open circuit voltage (Voc) and short-circuit current (Isc). The Internal Quantum Efficiency (IQE) measurement with better long wavelength response showed the wafer quality was much improved after LTA diffusion. To further investigate diffusion gettering performance, light-induced-degradation (LID) was analyzed both for LDE and LTA diffusion. The LID of LDE diffusion with 1.15%rel. is obviously higher than LTA diffusion of 0.46%rel., attributing to the higher iron concentration of LDE diffusion emitter to result in higher iron-boron pair dissociation. [ABSTRACT FROM AUTHOR]

In this paper, we focus on studying the low-temperature activated bulk TiZrV getter materials instead of thin film materials to meet the high reliability requirements of vacuum devices. The research was carried out by introduce Cu element to improve the activated characteristic and gettering performance. The XRD and in-situ XPS results showed the addition of Cu could effectively reduce the diffusion temperature and increase the diffusion rate of O atoms by modifying the phase structure of TiZrV getter. An appropriate amount of Cu was beneficial for stabilizing high-temperature β-Zr phase at room temperature, which had a larger interstitial void compared to that of the low-temperature α-Zr phase. The TiZrVCu getter with high proportion of β-Zr phase displayed 55.0% higher gettering performance than that of TiZrV with activated at 350 °C for 10 min. The proposed strategy of improving the low-temperature activated gettering performance offers promising opportunities for exploiting potential new low-temperature activated bulk getter materials. • Doping an appropriate amount of Cu to modify microstructure. • Increase interstitial void to improve low temperature activated gettering performance. • Study the effect of doping Cu via in-situ XPS and gas absorption characteristic test. [ABSTRACT FROM AUTHOR]

The impact of hydrocarbon-molecular (C3H6)-ion implantation in an epitaxial layer, which has low oxygen concentration, on the dark characteristics of complementary metal-oxide-semiconductor (CMOS) image sensor pixels was investigated by dark current spectroscopy. It was demonstrated that white spot defects of CMOS image sensor pixels when using a double epitaxial silicon wafer with C3H6-ion implanted in the first epitaxial layer were 40% lower than that when using an epitaxial silicon wafer with C3H6-ion implanted in the Czochralski-grown silicon substrate. This considerable reduction in white spot defects on the C3H6-ion-implanted double epitaxial silicon wafer may be due to the high gettering capability for metallic contamination during the device fabrication process and the suppression effects of oxygen diffusion into the device active layer. In addition, the defects with low internal oxygen concentration were observed in the C3H6-ion-implanted region of the double epitaxial silicon wafer after the device fabrication process. We found that the formation of defects with low internal oxygen concentration is a phenomenon specific to the C3H6-ion-implanted double epitaxial wafer. This finding suggests that the oxygen concentration in the defects being low is a factor in the high gettering capability for metallic impurities, and those defects are considered to directly contribute to the reduction in white spot defects in CMOS image sensor pixels.

The influence of the conditions of gettering in high-resistivity silicon during fabrication of PIN photodiodes on reverse dark currents has been studied. It is shown that gettering using a combination of phosphorus ion implantation and deposition of a polysilicon film with subsequent doping of the substrate rear side with phosphorus at temperatures below 900°C leads to low values of the reverse dark current and increases the nonequilibrium carrier lifetime. [ABSTRACT FROM AUTHOR]

Highlights • Graphitic carbon nitride was synthesized using two precursors, melamine and thiourea. • Physicochemical properties were confirmed by XRD, XPS and BET. • Inverse gas chromatography was employed to understand surface free energy of GCN. • The London dispersive parameters were determined by Schultz/Dorris–Gray methods. • The Lewis acid–base parameters, showing the more basic character of GCN. Abstract Melamine and thiourea-derived graphitic carbon nitrides (M-GCN/T-GCN) were synthesized and characterized. The surface properties were investigated using inverse gas chromatography (IGC) and compared. Net retention volumes of M-GCN and T-GCN were measured with n -alkanes (C 5 –C 10) and polar probes. The London dispersive surface free energies (γ s d), calculated using Schultz and Dorris–Gray methods, decreased linearly with increasing temperature. The specific components of the enthalpy and entropy of adsorption for the polar probes were obtained using the Schultz, Dong, and Sawyer–Brookman methods. The Gutmann's Lewis acid–base parameters, K a and K b , were determined using the surface free energy (Δ G a S) via these methods. The surface character ' S' values (K b / K a) of M-GCN and T-GCN using the respective methods are 4.04, 3.78, and 5.08 and 4.11, 5.27, and 2.86. Hence, the surfaces contain more basic than acidic sites and could interact strongly with acidic media. Thus, IGC elucidates the surface charges of the GCN matrix resulting from surface chemical modification. [ABSTRACT FROM AUTHOR]

Abstract This work investigates the effect of laser microgrooved monocrystalline silicon surfaces to improve the gettering effectiveness of Si substrates for enhanced solar cell electrical properties. A combination of microgrooves and a grown sacrificial porous silicon layer (PSL), subjected to a heat treatment at different temperatures was considered to point out the crucial role of the microgrooves during the gettering procedure. This treatment leads to a significant decrease of the impurities concentration and recombination activities, in addition to a noticeable enhancement of light trapping, enabling an increased carrier collection probability. The microgrooves were made by means of NWR 213 laser ablation system. The PS layers were performed by a thermal activated stain etching method that will act as sacrificial trapping layers of the gettered impurities. The topography of the patterned surfaces with and without PSLs was investigated using field emission scanning electron microscopy (FESEM). As we expected, the combination of microgrooves with higher density at both surfaces and PSL improved obviously the optoelectronic properties of the processed solar cells. The minority carrier lifetime measured by means of the photoconductive decay method (PCD) was significantly increased from 9.2 μsec to 89 μsec. The Hall Effect measurement shows a significant increase of the carrier mobility. Moreover, the dark I V characteristics and the internal quantum efficiency (IQE) found to be improved. An apparent enhancement of the open circuit voltage V oc and current density J sc was obtained indicating improved solar cell electrical properties. Highlights • Important decrease of the recombination activities after gettering the microgrooved substrates. • The combination of laser microgrooves and porous silicon layer at both surfaces increased the open circuit voltage and the current density. • Significant enhancement of the effective minority carrier lifetime and internal quantum efficiency (IQE). [ABSTRACT FROM AUTHOR]

Abstract Nano-engineered composite film, prepared by the combination of titanium (Ti) nanoparticles with surrounding layers of palladium (Pd), has been suggested as a high performance hydrogen (H 2) getter. Uniform Ti Pd film covered by a 35-nm-thick Pd layer was deposited on a silicon wafer via cosputtering and post-vacuum-annealing. As the annealing temperature increased from 200 to 400 °C, amorphous alloy and nano-aggregates were observed, and efficient structural modulation occurred at 400 °C, where dewetting of Pd cover layer from the getter surface was observed. This led to the enhancement of the chemisorption capacity of the 400oC-annealed sample, two-times higher than that of the 300oC-annealed sample. Abrupt change in residual gases, which typically come from a bonding process, can be mitigated by minimizing the gas transfer distance through the dewetting of the cover layer; since Ti nanoparticles surrounded by Pd exist independently of each other in the gettering layer, external H 2 gas molecules can be continuously adsorbed onto still-unreacted Ti particles by passing through the dewetted channels in the Pd cover layer. This concept demonstrates a pathway towards a useful synthetic approach for high-performance thin-film getters with high adsorption capacity, fast gettering rate and good device compatibility. Highlights • Nanostructured Ti Pd/Pd film was synthesized by cosputtering and post-vacuum-annealing for H 2 getter. • Nano-aggregates in getter film and dewetting of Pd cover layer were observed after annealing at 400 °C. • H 2 adsorption isotherms showed high performance chemisorption capacity of nano-engineered Ti Pd/Pd film. • Ti nanoparticles surrounded by Pd exist independently of each other, and thus can continuously adsorb H 2. [ABSTRACT FROM AUTHOR]

Adsorption process plays an important role in the removal of phosphorus from aqueous solutions. A laboratory experiment was conducted to investigate the adsorption characteristics of phosphorus onto natural zeolite and to find out the relative importance of some controllable treatments in phosphorus adsorption process using the Taguchi optimization methodology. Results showed that the adsorption of phosphorus in the presence of Fe3+ and Al3+ was higher than that in the absence of these two cations probably due to the adsorption of phosphorus-bearing anions on opposite charges of these cations. Also, increase in contact time tended phosphorus adsorption to be increased. The addition of base and acid treatments caused an increase and a decrease, respectively, on phosphorus adsorption. The order of effectiveness of treatments on the values of phosphorus adsorption was as follows: acid/base treatment >sorbent to sorbate ratio > modification with aluminium (Al)/iron (Fe) >contact time >phosphorus concentration. Phosphorus adsorption data well fitted to the Freundlich isotherm model. The pseudo-second order was the best model describing phosphorus adsorption kinetics. According to the results reported herein, it is assumed that the main mechanism controlling phosphorus adsorption onto natural zeolite is chemisorption. [ABSTRACT FROM AUTHOR]

The carbon dioxide sorption process at coal seams is very important for understanding the trapping mechanisms of carbon capture and storage. The gas retention capacity of coal seams can be estimated using indirect methods based on the adsorption/desorption isotherms obtained in the laboratory. However, the gas sorption capacity can be overestimated or underestimated depending on the sample preparation. This work evaluates different sample preparations and their theoretical adsorption capacity using coal samples from the Cambui coal field (Parana Basin), southern Brazil. Experiments using a thermogravimetric balance were done to calculate the theoretical adsorption capacity, while sample characterization was done through immediate analysis, elementary analysis, and mineralogical studies. The sample preparations used in this work were powder, pellets, and fragments. While the powder form presents an average behavior, without any experimental complication, the pellet is extremely sensitive to any variation in the sample preparation, such as fractures, and the fragment requires a much longer experiment time than the other sample preparations, being impracticable for some cases. [ABSTRACT FROM AUTHOR]

In the context of the continuous price reduction in photovoltaics (PV) in recent years, Si feedstock continues to be a relevant component in the cost breakdown of a PV module, highlighting the need for low-cost, low-capital expenditure (CAPEX) silicon technologies to further reduce this cost component. Upgraded metallurgical-grade silicon (UMG Si) has recently received much attention, improving its quality and even attaining, in some cases, solar cell efficiencies similar to those of conventional material. However, some technical challenges still have to be addressed when processing this material to compensate efficiently for the high content of impurities and contaminants. Adaptation of a conventional solar cell process to monocrystalline UMG Si wafers has been studied in this work. In particular, a tailored phosphorus diffusion gettering step followed by a low-temperature anneal at 700°C was implemented, resulting in enhanced bulk lifetime and emitter recombination properties. In spite of the need for further research and material optimization, UMG Si wafers were successfully processed, achieving efficiencies in the range of 15% for a standard laboratory solar cell process with aluminum back surface field. [ABSTRACT FROM AUTHOR]

Reducing light and elevated temperature induced degradation (LeTID) is important for the industrial success of PERC (passivated emitter and rear cell) solar cells fabricated on high‐performance multicrystalline silicon (multi‐Si) wafers. Although there has been a lot of progress in understanding the degradation kinetics, the defect(s) responsible for LeTID in multi‐Si wafers at elevated temperatures (≈80 °C, 1 Sun) has yet to be identified. In this study, the authors look at the possibility of using phosphorus diffusion gettering (PDG) for reducing LeTID in multi‐Si wafers and solar cells. By measuring light induced defect concentrations in multi‐Si wafers before and after LeTID, the authors observe that PDG can substantially reduce the average defect concentration. Trace element analysis using inductively coupled plasma mass spectrometry reveals that multi‐Si wafers from the edge of the ingot contain a high concentration of Cu, Ni and Ti in grains that degrade more than neighboring grains. To explore PDG for reducing LeTID in multi‐Si PERC solar cells, the authors fabricate cells with two different emitter profiles. Etching back a heavily diffused emitter to obtain a high sheet resistance is observed to improve the LeTID performance of the solar cells, an effect that is very likely related to a reduced impurity concentration within the wafer. [ABSTRACT FROM AUTHOR]

This paper presents direct experimental evidence for the strong impurity gettering effects associated with the formation of both phosphorus and boron doped polysilicon/oxide passivating contacts for silicon solar cells, doped via thermal diffusion from POCl 3 or BBr 3 sources. Ion-implanted iron is used as a marker to quantify the gettering effectiveness via carrier lifetime measurements. The process conditions for fabricating optimum polysilicon passivating contacts are found to remove more than 99.9% of the iron from the silicon wafer bulk. The gettering effects of POCl 3 and BBr 3 diffused polysilicon/oxide contacts mainly arise from the dopant diffusions, as opposed to gettering by structural defects in the polysilicon films. The thin oxide interlayer hinders the gettering effectiveness at low diffusion temperatures, although its blocking effect becomes small at the moderate temperatures used to fabricate optimum polysilicon contacts. The gettering effectiveness increases with increasing diffusion temperature. The gettering of iron from the silicon wafer bulk to the surface layers is found to have a negligible impact on their ability to suppress recombination at the interface with the silicon wafer. Therefore, the formation of polysilicon/oxide passivating contacts, via thermal diffusion from POCl 3 and BBr 3 sources, not only achieves high quality surface and contact passivation but also has the net additional benefit of achieving very effective gettering of unwanted impurities in the silicon wafer bulk. [ABSTRACT FROM AUTHOR]

The polysilicon gettering behavior of iron (Fe) and copper (Cu) in highly boron doped silicon was studied under isothermal annealing with and without the presence of an electric field. Depth profiles of Fe and Cu in the polysilicon were obtained by dynamic secondary ion mass spectrometry. Enhanced gettering as a result of the electric field can be attributed to the drift-behavior of Fe and Cu over thermal diffusion at elevated temperature. While the polysilicon-silicon interfacial segregation acted against the back-diffusion of Cu, the same was not observed for Fe. About 61% of Cu and 35% of Fe were trapped in polysilicon after 2 days owing to strong interfacial segregations. [ABSTRACT FROM AUTHOR]

Aluminium oxide (Al2O3) thin films deposited on silicon surfaces, synthesised by plasma‐assisted atomic layer deposition, are recently reported to possess impurity gettering effects for the silicon wafer bulk during annealing at 425 °C, a typical temperature used for activating the surface passivation quality of the Al2O3 films. This paper investigates the gettering effects of Al2O3 films at higher temperatures of 700–900 °C, which are commonly used for contact firing in silicon solar cell fabrication. Iron is used as a marker impurity in silicon to study the gettering effectiveness. Results show that Al2O3 films also generate strong impurity gettering effects at 700–900 °C, through a segregation gettering mechanism. The as‐deposited Al2O3 films are found to be more effective at gettering than the 425 °C‐activated Al2O3 films, demonstrating gettering processes that are largely limited by the impurity diffusivity in silicon. For both as‐deposited and activated Al2O3 films, gettering during high temperature annealing occurs by impurity accumulation at the Al2O3/Si interfaces, similar to the gettering action at 425 °C. However, some iron is found to redistribute into the bulk of the Al2O3 films after long annealing at a high temperature. [ABSTRACT FROM AUTHOR]