Search

The composition dependent magnetic structure in epitaxial BaFe12-xScxO19 (0 ≤ x ≤ 2.1, BaScM) thin films have been investigated. Results show that with increasing Sc3+ content, the out-of-plane c-axis lattice constants of BaScM films increase but do not follow the Vegard's law. The changes in hysteresis loops indicate a variation of magneto-crystalline anisotropy from the uniaxial-type for BaFe12O19 to the near-planar type for BaFe10.2Sc1.8O19. The remanent magnetic domains change from a mixture of dots and maze-like structure to more maze-like structure as the Sc3+ content increases. The above magnetic results can be explained by a composition dependent magnetic structure transition from collinear-type ferrimagnetic magnetic structure to the non-collinear conical magnetic structure which appears at Sc3+ content x ≥ 0.6. The ZFC/FC curves further show that the conical magnetic structure transition temperature (Tcone) of the films increases with the Sc3+ content until x ≥ 2.1. The above results may help better apply BaScM films in the electromagnetic devices.

Aiming at the problems of STL model such as data redundancy, lack of geometric logic relationship in industrial engineering, a new method about direct topological structure reconstruction for STL model programming was proposed. In that way, the topological structure of geometrical relationship could be quickly established. Based on Python, three types of geometric data and four adjacency tables for the topology data were built by using the embedded variables of list and tuple. Then the facets data in STL file were processed one by one and stored in the designed topological structure. Finally, the topological data was loaded into PythonOCC, and topological data of several models were tested. Experimental results proved that the topological structure reconstruction for STL model was effective.

The popularity of online gambling could bring negative social impact, and many countries ban or restrict online gambling. Taking China for example, online gambling violates Chinese laws and hence is illegal. However, illegal online gambling websites are still thriving despite strict restrictions, since they are able to make tremendous illicit profits by trapping and cheating online players. In this paper, we conduct the first deep analysis on illegal online gambling targeting Chinese to unveil its profit chain. After successfully identifying more than 967,954 suspicious illegal gambling websites, we inspect these illegal gambling websites from five aspects, including webpage structure similarity, SEO (Search Engine Optimization) methods, the abuse of Internet infrastructure, third-party online payment, and gambling group. Then we conduct a measurement study on the profit chain of illegal online gambling, investigating the upstream and downstream of these illegal gambling websites. We mainly focus on promotion strategies, third-party online payment, the abuse of third-party live chat services, and network infrastructures. Our findings shed the light on the ecosystem of online gambling and help the security community thwart illegal online gambling.

An ultrathin layer of SiOx formed on the surface of a silicon solar cell can significantly reduce the potential induced degradation effect in solar cell modules. In this work, a liquid oxidation (LO) technique was developed to oxidize silicon surfaces by using a Ti/IrO2–CoO2 anode that can produce a large amount of hydroxyl radicals (•OH) and other species. Our results indicate that the LO SiOx (2.5 nm) layer is very dense, thus the modules made from LO treated cells are better able to mitigate potential induced degradation than modules made from ozone oxidized cells.

The magnetic properties of conical magnetic structure (CMS) hexaferrites BaFe10.2Sc1.8O19 (BFSO) and SrFe10.2Sc1.8O19 (SFSO) have been investigated under different magnetic fields and different temperatures. Results show that the single phase CMS hexaferrites BFSO and SFSO can be obtained as the sintering temperature exceeds 1473 K. Both the coercivity Hc and remanent magnetization Mr of the CMS BFSO and SFSO decrease sharply with increasing temperature below 100 K, and they become very small and almost invariant when the temperature exceeds 100 K. For both BFSO and SFSO, the field-cooling and zero-field-cooling curves differ greatly at low temperatures and resemble at high temperatures. A magnetic transition temperature Tz2 from noncollinear CMS to collinear ferrimagnetic structure is observed in both BFSO and SFSO with BFSO having higher Tz2 than that of SFSO. Moreover, the Tz2 decreases with increasing the magnetic field in both samples generally.

For increasing accuracy rate of landing risk assessment of carrier-based aircraft, this article is committed to research on landing risk assessment of carrier-based aircraft based on mean-variance dynamic multi-attribute decision making. Attribute values are provided in the form of triangle fuzzy number. Mean sort values is acquired by formula of possibility degree and order. For solving a problem of the same or similar orders, the improved method combines mean and variance, analyzing and judging, getting alternatives rank. Finally, the feasibility and availability of the improved method is proved by simulation results.

The introduction of ozonated deionized water (DIO3 water) to the silicon wafer wet cleaning process has attracted interest from the photovoltaic industry. In this work, a simple and cost-effective approach to fabricate submicron-texture multicrystalline silicon (mc-Si) wafer is presented using Ag metal-catalyzed chemical etching (MCCE) in DIO3/HF solution, where DIO3 was used as a hole injecting agent. The submicron-texture was successfully applied to fabricate efficient mc-Si PERC solar cells with an average efficiency of 20.31%, which is 0.58%abs higher than those with an acid micron-texture and exceeds those with conventional MCCE submicron-textures using H2O2 as the hole injecting agent. We demonstrated that using DIO3 as a hole injection agent in metal-catalyzed chemical etching is feasible. This novel MCCE approach is simple, low-cost, and ecofriendly, making it an attractive alternative to conventional MCCE methods for use in industrial-scale production.

Black silicon contains high-aspect-ratio micro/nanostructures with greatly suppressed front-surface reflection, thus possessing superior property in photoelectric devices. In this report, by a two-step copper-assisted chemical etching method, we have fabricated pyramid n+p-black silicon with optimized morphology and anti-reflectance capability, through systematically tuning the concentration of both copper ions and reducing agents, as well as the etching time. The improved optical absorption and superior charge transfer kinetics validate n+p-black silicon as a highly active photocathode in photoelectrochemical cells. The onset potential of 0.21 V vs. RHE and the saturation photocurrent density of 32.56 mA/cm2 are achieved in the optimal n+p-black silicon. In addition, the nanoporous structure with lower reflectance is also achieved in planar p-silicon via the same etching method. Moreover, the photodetectors based on planar p-black silicon show significantly enhanced photoresponsivity over a broad spectral range. This study offers a low-cost and scalable strategy to improve the photoelectric-conversion efficiency in silicon-based devices.

Alkali solutions are not suitable for texturing multi-crystalline silicon (mc-Si) wafer due to the anisotropic etching. In this study, a two-step alkali-etch process is developed to form a flat surface on the wafer, which can be quickly and nearly isotropically etched by immersion in a sodium hydroxide solution, followed by a sodium hydroxide-sodium hypochlorite solution. The etching process leads to the formation of homogenous nanostructure, thereby improving the cell's repeatability and performance by simultaneously increasing its short-circuit current and open-circuit voltage.

International audience; MACE nano-texture process applicable for both single-and multi-crystalline diamond-wire sawn Si solar cells. ABSTRACT The photovoltaic (PV) industry requires efficient cutting of large single and multi-crystalline (sc-and mc-) silicon (Si) wafers. Historically multi-wire slurry sawing (MWSS) dominated, but the higher productivity of diamond-wire-sawing (DWS) holds promise for decreasing PV costs in the future. While surface texturing of DWS wafers is more complicated than of MWSS wafers, especially in mc-Si wafers, nanotexturing has been shown to overcome this challenge. While the benefit of nanotexturing is thus clearer in mc-Si, a universal nano-texture process that also works on sc-Si would simplify and reduce the investments costs of PV production-lines. In this paper, such a nano-texture process is developed using a metal-assisted chemical etch (MACE) technique. Step-by-step characterization of surface structure and reflectance of the MACE process is used after: 1) wafering, 2) standard acidic texturing etch, 3) silver nanoparticles deposition, and 4) MACE nanotexturing for both sc and mc-Si. The results show that the same MACE process works effectively for both sc-Si and mc-Si wafers. Finally, the nano-textured wafers are processed into PV cells in an industrial process line with conversion efficiencies of 19.4 % and 18.7%, for sc-Si and mc-Si solar cells, respectively.

In this paper, we present a large-scale analysis about an emerging new type of domain-name fraud, which we call levelsquatting. Unlike existing frauds that impersonate well-known brand names (like google.com) by using similar second-level domain names, adversaries here embed brand name in the subdomain section, deceiving users especially mobile users who do not pay attention to the entire domain names.

Compared with traditional precious metal catalysts, MoS2 is regarded as the promising hydrogen evolution reaction catalyst for Si photocathodes, because of its higher photochemical stability and lower hydrogen adsorption free energy. However, the layers of MoS2 are connected by van der Waals force, and the interaction force between the layers of MoS2 and Si is weak. Therefore, the homogeneous MoS2 nanosheets directly synthesized on Si by the hydrothermal method remain challenging. Herein, we report a facile strategy for the fast and efficient growth of vertically standing MoS2 on pyramid Si via surface hydrophilicity tailoring by inserting a thin TiO2 layer. Thanks to the improved light trapping and catalytic kinetics, the optimal MoS2/TiO2/Si shows a short-circuit photocurrent density of 9.79 mA/cm2 and an onset potential of 0.31 V vs reversible hydrogen electrode under 100 mW/cm2 Xe‐lamp illumination. By comparing with different oxide buffer layers, surface hydrophilicity is found to be essential for promoting the homogenous nucleation and growth of vertically standing MoS2 by the hydrothermal method. These results not only provide valuable insight into the growth kinetics of transition metal chalcogenides in aqueous solution but also deliver an efficient route for assembling noble-metal free catalysts on silicon-based photoelectrodes.

A laser texturing process including laser ablation and post-etching has been developed to form a unique microstructure of pits in craters (PIC) on the front surface of the diamond wire sawn multi-crystalline silicon (DWS mc-Si) wafer. A laser ablation is applied to produce craters with size of tens of microns distributed at the front surface of the wafer, followed by a post-etching process to remove silicon slags produced in the laser process and to form the pits of size in few microns embedded in each crater. The structural, optical and electrical characteristics of the PIC structure are investigated and optimized to achieve a good trade-off between light trapping and recombination. Finally, an applicative laser texturing process is demonstrated for the industrial-grade DWS mc-Si solar cells with an increased efficiency of 19.26% compared with the standard acid textured ones (19.10%).

The microstructure and magnetic properties of Ta/Ni81Fe19/Ta tri-layer thin films on three types of mono-like cast silicon substrates (flat, upright pyramid and inverted pyramid surfaces) were investigated. Results show that the surface topography structures of the films followed those of the substrates generally. But the thickness of the film on pyramid surface increases from the pyramid tip to the bottom. This is caused by the anisotropical diffusion of incident atoms/ions on the pyramid surfaces during the film growth process. The films on pyramid structured substrates have smaller saturation magnetizations but larger in-plane coercivity than that of on the flat substrate. This should be mainly caused by the non-zero angle between the magnetic field and the substrates as suggested by the angular dependent magnetic properties of the films. The hysteresis loops measured from in-plane to out-of-plane directions show that the coercivities of films on all the mono-like cast silicons are highly angular dependent. A further post-annealing of the films suggests that the magnetic properties of the films are dominantly determined by the surface microstructure of substrates instead of the fabrication conditions. The above results can help better integration of NiFe thin films on mono-like cast silicon based devices.

In this paper, an improved 2-optimization(2-opt) and Ant Colony Optimization (ACO) Hybrid Algorithm is proposed to solve the Traveling Salesman Problem (TSP). The improved scheme of ACO is to define the indirect expectation heuristic and introduce it into the calculation method of transition probability, which will reduce the effect of pheromone on ant selecting path and increase the path's diversity of ACO. In this way, the deficiency of ACO in convergence to local optimal solution will be made up. Considering of the stronger local search ability, 2-opt algorithm is used to optimize existing solutions, and the better solution is obtained. Finally, the performance of the proposed algorithm is evaluated by the classical TSP problem.

Online underground economy is an important channel that connects the merchants of illegal products and their buyers, which is also constantly monitored by legal authorities. As one common way for evasion, the merchants and buyers together create a vocabulary of jargons (called "black keywords" in this paper) to disguise the transaction (e.g., "smack" is one street name for "heroin" [1]). Black keywords are often "unfriendly" to the outsiders, which are created by either distorting the original meaning of common words or tweaking other black keywords. Understanding black keywords is of great importance to track and disrupt the underground economy, but it is also prohibitively difficult: the investigators have to infiltrate the inner circle of criminals to learn their meanings, a task both risky and time-consuming. In this paper, we make the first attempt towards capturing and understanding the ever-changing black keywords. We investigated the underground business promoted through blackhat SEO (search engine optimization) and demonstrate that the black keywords targeted by the SEOers can be discovered through a fully automated approach. Our insights are two-fold: first, the pages indexed under black keywords are more likely to contain malicious or fraudulent content (e.g., SEO pages) and alarmed by off-the-shelf detectors, second, people tend to query multiple similar black keywords to find the merchandise. Therefore, we could infer whether a search keyword is "black" by inspecting the associated search results and then use the related search queries to extend our findings. To this end, we built a system called KDES (Keywords Detection and Expansion System), and applied it to the search results of Baidu, China's top search engine. So far, we have already identified 478,879 black keywords which were clustered under 1,522 core words based on text similarity. We further extracted the information like emails, mobile phone numbers and instant messenger IDs from the pages and domains relevant to the underground business. Such information helps us gain better understanding about the underground economy of China in particular. In addition, our work could help search engine vendors purify the search results and disrupt the channel of the underground market. Our co-authors from Baidu compared our results with their blacklist, found many of them (e.g., long-tail and obfuscated keywords) were not in it, and then added them to Baidu's internal blacklist.

The VO2/Pb(Zr0.52Ti0.48)O3 (PZT) thin film heterostructure device was first grown to investigate the piezoelectric control of resistance switching in Vanadium dioxide (VO2) films with a PZT underlayer. The results show that upon applying a continuous gate-electric-field (Eb) on the heterostructure, a butterfly shape resistance (R) vs. Eb curve of VO2 was observed. This R-Eb curve agrees well with the strain vs. electric-field “butterfly” curve of the underlying PZT, indicating that the resistance changes in VO2 were induced by piezoelectric lattice strain at the VO2/PZT interface. A repeated pulsed Eb modulation of VO2 resistance was further demonstrated. The resistance of the VO2 film decreases under compressive strain and increases under tensile strain. The resistance of change of the VO2 film under different strains has been explained using the first-principles calculations. The above results show that repeatable resistance switching in the VO2 film can be realized in the VO2/PZT heterostructure with a small Eb around room temperature.The VO2/Pb(Zr0.52Ti0.48)O3 (PZT) thin film heterostructure device was first grown to investigate the piezoelectric control of resistance switching in Vanadium dioxide (VO2) films with a PZT underlayer. The results show that upon applying a continuous gate-electric-field (Eb) on the heterostructure, a butterfly shape resistance (R) vs. Eb curve of VO2 was observed. This R-Eb curve agrees well with the strain vs. electric-field “butterfly” curve of the underlying PZT, indicating that the resistance changes in VO2 were induced by piezoelectric lattice strain at the VO2/PZT interface. A repeated pulsed Eb modulation of VO2 resistance was further demonstrated. The resistance of the VO2 film decreases under compressive strain and increases under tensile strain. The resistance of change of the VO2 film under different strains has been explained using the first-principles calculations. The above results show that repeatable resistance switching in the VO2 film can be realized in the VO2/PZT heterostructure with a...

In this paper, we demonstrate that the performance of the industrial multicrystalline silicon solar cells can be improved by embedding the silver nanoparticles (Ag-NPs) into the SiNx layer. On the one hand, the cells have a certain optical loss in short wavelengths near the plasmonic resonance frequency of Ag-NPs, but their open circuit voltages and filling factors are increased due to depressed surface recombination as those short wavelength photons are mainly absorbed by Ag-NPs instead of the surface; on the other hand, the cells show strong absorption in long wavelengths, which can be attributed to the forward-scattering effect of Ag-NPs. Taking together, UV-absorbing Ag-NPs may act as a “sunscreen” to shield the UV damage, while improve the cell efficiency from 18.05 % to 18.25 % by embedding proper Ag-NPs. The techniques presented in this work can be easily incorporated into the current mc-Si solar cell production line, thus have great potential for the mass practical application.

A multi-unit device for photocatalytic degradation that contained a silicon solar cell module and two TiO2/Ti electrodes was fabricated. The TiO2/Ti electrodes were connected to Al (positive) and Ag (negative) electrodes of the module. The silicon solar cell module efficiently converted photons to electron-hole pairs, and the two well-designed TiO2/Ti Schottky junction electrodes transported the electrons and holes to the planar TiO2 surface. The combination of a silicon solar cell module and TiO2 gave excellent photocatalytic degradation activity beside simple and flexible fabrication. Importantly, this device showed great potential in the degradation of organic pollutants in water bodies.

Black silicon (Si) photoelectrodes are promising for improving the performance of photoelectrochemical (PEC) water splitting. Here, we report the fabrication of p-black Si and n+p-black Si photocathodes via a controllable copper-assisted catalyzed etching method. The etching process affects only the topmost less than 200 nm of Si and is independent of the surface doping. The synergistic effects of the excellent light harvesting of the black Si and the improved charge transfer properties of the p-n junction boost the production and utilization of photogenerated carriers. The mean reflectance of the pristine Si samples is about 10% from 400 to 950 nm, while that of the black Si samples is reduced as low as 5%. In addition, the PEC properties of the n+p-black Si photocathode can be further enhanced by depositing a cobalt (Co) layer. Compared with the p-Si sample, the onset potential of the Co/n+p-black Si photocathode is positively shifted by 560 mV to 0.33 V vs. reversible hydrogen electrode and the saturation photocurrent density is increased from 22.7 to 32.6 mA/cm2. The design of the Co/n+p-black Si photocathode offers an efficient strategy for preparing PEC solar energy conversion devices.

Polycrystalline ferroelectric BiFeO3 (BFO) films deposited on transparent indium tin oxide (ITO) electrodes have shown to be an interesting photocathode for photoelectrochemical (PEC) water splitting; however, its PEC performance and stability are far from perfection. Herein, we reported an amorphous TiO2 buffer layer, inserted between BFO and Pt catalyst, improves significantly both its PEC activity and stability. A photocathodic current density of −460 μA/cm2 at 0 V vs. reversible hydrogen electrode (RHE) and an onset potential of 1.25 V vs. RHE were obtained in ITO/BFO/TiO2/Pt photocathode under 100 mW/cm2 Xe-lamp illumination. TiO2 functions as a buffer layer to remove the upward barrier between BFO and Pt, and makes the photogenerated carriers separate efficiently. The photocathode also shows high stability in acid solution after a 10-h PEC continuous testing.

Mass production of diamond-wire-sawn (DWS) multicrystalline silicon (mc-Si) solar cells reached a significant point of maturity through utilization of metal-catalyzed chemical etching (MCCE). However, nanotextured DWS mc-Si solar cells usually produced with Ag-MCCE still suffer from certain drawbacks, such as remaining saw marks, color differences among grains, and slight decreases in the open-circuit voltage (Voc). In this work, we show that unoriented Cu-based MCCE (Cu-MCCE) not only depresses the saw marks and color differences but also introduces random shallow pits, which act as artificial defects that can be easily converted into a submicron texture using conventional HNO3/HF etching. Moreover, we demonstrate that the efficiency of DWS mc-Si solar cells produced with the Cu-MCCE process is greater than 19%, with improved Voc resulting from better surface passivation. This cost-effective Cu-MCCE method is, therefore, of significant potential for the photovoltaic industry.

BiFeO3 (BFO)-based ferroelectrics have been proved to be visible-light-driven photoelectrodes for O2 production. However, the hitherto reported photoelectrochemical performances remain inferior to meet the requirements for any applications. Besides, expensive noble metals (Ag, Au) are commonly required to achieve high photoelectric conversion efficiency. Here, the significant enhancements of photoelectrochemical performance is reported by fabricating a noble-metal-free reduced graphene oxide (RGO)/BFO composite film via a simple and cost-effective solution process. The optimized RGO/BFO composite film exhibits a 600% improvement of the short-circuit photocurrent density compared to that of the pristine BFO, and also outperforms the noble-metal/BFO cells under the same reaction conditions. Furthermore, the incident photon-to-current efficiency of the optimized RGO/BFO sample shows threefold enhancement. This study delivers a facile and low-cost approach to preparing 2D materials/ferroelectric heterostructures and offers a promising pathway to boost the performance of semiconducting ferroelectric photoelectrodes.

For efficient utilization of solar light during photoelectrochemical (PEC) water splitting, tandem photoelectrodes comprising a wider bandgap top semiconductor stacked above a smaller bandgap one have been proposed in the previous studies. However, the photocurrent is usually limited due to the blocked transfer of photogenerated carriers on the interface between the semiconductors. Here, this study constructs an Si-pnn+/ITO/Au/BiFeO3 (BFO) hybrid photocathode catalyzed by MoS2/Pt with an intension to fulfill the efficient transfer of photogenerated electrons from Si to electrode surface. This study reveals how the local surface plasmonic resonance effect of Au nanoparticles and the depolarization electric field of BFO enhance the PEC reactivity of the photocathode, and also the catalytic effect of the combined MoS2/Pt catalyst. Remarkably, the photocathode exhibits an onset potential of 1.3 V versus reversible hydrogen electrode (RHE), and the photocurrent at 0 V versus RHE can be up to –9.1 mA cm−2 under 100 mW cm−2 Xe-lamp illuminations. Such a unique design represents a general strategy to enhance the PEC performance of a tandem photoelectrode where the energy bands are not so matched on the interfaces, and therefore extends the scope of the tandem architectures.

MoS2 has been studied as an efficient and cheap hydrogen evolution reaction (HER) catalyst; however, its effective integration with a photocathode remains a challenge. Here, crystalline MoS2 catalyst was deposited on top of a ∼2 nm Al2O3 protected n+p-Si photocathode using a simple photoreduction method following a post-annealing. The amount of MoS2 is optimized for HER of the photocathode, balanced between its catalytic effect and light absorption. High efficiency with 0.35 V onset potential vs. reversible hydrogen electrode and 34.5 mA/cm2 saturated photocurrent and high stability after 2 min ultrasonication or under 40 h continuous HER were observed. Such properties are much superior to the corresponding photocathodes coated by the traditional electrodeposited amorphous MoS2. Furthermore, the MoS2 layer is also an effective support for Pt nanoparticles with considerable reduction in the Pt amount while keeping the photoelectrochemical reactivity. This study indicates that the cheap-made MoS2 can be an efficient and stable HER catalyst for the Si photocathode.

Single-crystalline silicon is one of a few promising substrate materials on which to grow NbTiN ultrathin films for applications in superconducting single photon detection devices. In this work, a buffer layer of phosphorus silicate glass (PSG) ~250 nm is formed rapidly on the silicon substrate under a relatively low temperature to ease the mismatching between NbTiN and substrate, and simultaneously act as an antireflection layer at the working wavelength. (111)-oriented NbTiN films were deposited on both SiO2/Si and PSG/Si substrates by using a dc reactive magnetron co-sputtering system of independent Nb and Ti targets. The superconducting critical temperature T c of the 5 nm-NbTiN/PSG/Si sample reaches ~8.8 K due to effectively relieving the mismatch between NbTiN and Si by PSG buffer layer.