Avalanche Carrier Multiplication in Multilayer Black Phosphorus and Avalanche Photodetector

A highly sensitive avalanche photodetector (APD) is fabricated by utilizing the avalanche multiplication mechanism in black phosphorus (BP), where a strong avalanche multiplication of electron–hole pairs is observed. Owing to the small bandgap (0.33 eV) of the multilayer BP, the carrier multiplication occurs at a significantly lower electric field than those of other 2D semiconductor materials. In order to further enhance the quantum efficiency and increase the signal‐to‐noise (S/N) ratio, Au nanoparticles (NPs) are integrated on the BP surface, which improves the light absorption by plasmonic effects. The BP–Au‐NPs structure effectively reduces both dark current (≈10 times lower) and onset of avalanche electric field, leading to higher carrier multiplication, photogain, quantum efficiency, and S/N ratio. For the BP–Au‐NPs APD, it is obtained that the external quantum efficiency (EQE) is 382 and the responsivity is 160 A W^‐1 at an electric field of 5 kV cm^‐1 (V_d ≈ 3.5 V, note that for the BP APD, EQE = 4.77 and responsivity = 2 A W^‐1 obtained at the same electric field). The significantly increased performance of the BP APD is promising for low‐power‐consumption, high‐sensitivity, and low‐noise photodevice applications, which can enable high‐performance optical communication and imaging systems.     

An experimental study of the characteristics of hydrostatic transmission systems

In the field of robotics, mechanical power transmission systems are fundamental and critical components. In recent years, hydrostatic transmission systems (HSTs) have begun to receive attention as power transmission systems for robotic applications. The primary goal of this study is to identify the inherent properties of HSTs. In this article, we first introduce experimental methods for determining the characteristics of HSTs and then discuss the experimental results. Our findings from the experiments suggest that the commercial external gear pump in an HST cannot entirely convert mechanical power to hydraulic power because of its internal leakage and friction behavior. These physical behaviors are mathematically modeled and experimentally identified. It is also found that a long transmission line not only results in low-pressure rise rates but also flow friction loss. We strongly believe that the results discussed in this article will provide helpful guidance for the design and control of robotic systems.     

Campaign Ads, Online Messaging, and Participation: Extending the Communication Mediation Model

Political communication researchers have devoted a great deal of attention to the role of political advertising, the Internet, and political discussion in civic and political life. In this article, we integrate and extend this research by developing a campaign communication mediation model of civic and campaign participation. Two data sets are merged for this inquiry: (a) content-coded ad-buy data on the placement of campaign messages on a market-by-market and program-by-program basis and (b) a national panel study concerning patterns of traditional and digital media consumption and levels of civic and campaign participation. Exposure to televised campaign advertising is estimated by developing an algorithm based on the market and program placement of specific ads and geocoded survey respondents' viewing of certain categories of television content in which these ads were concentrated. Structural equation models reveal that advertising exposure drives online news use in ways that complement conventional news influences on political discussion and political messaging. However, campaign exposure emphasizing "attack" messages appears to diminish information seeking motivations via broadcast and print media, yet only indirectly and weakly suppresses participation in civic and political life. Further, alternative specifications reveal that our original model produces the best fit, empirically and theoretically. We use these insights to propose an O-S-R-O-R (orientations-stimuli-reasoning-orientations-responses) framework as an alternative to the longstanding O-S-O-R model in communication and social psychology.     

Domestic wastewater treatment as a net energy producer--can this be achieved?

In seeking greater sustainability in water resources management, wastewater is now being considered more as a resource than as a waste-a resource for water, for plant nutrients, and for energy. Energy, the primary focus of this article, can be obtained from wastewater's organic as well as from its thermal content. Also, using wastewater's nitrogen and P nutrients for plant fertilization, rather than wasting them, helps offset the high energy cost of producing synthetic fertilizers. Microbial fuel cells offer potential for direct biological conversion of wastewater's organic materials into electricity, although significant improvements are needed for this process to be competitive with anaerobic biological conversion of wastewater organics into biogas, a renewable fuel used in electricity generation. Newer membrane processes coupled with complete anaerobic treatment of wastewater offer the potential for wastewater treatment to become a net generator of energy, rather than the large energy consumer that it is today.     

Nanopatterned silicon emitters of a solar cell fabricated by anodic aluminum oxide masks

We investigated the nanopattern transferring process by a template of anodic aluminum oxide and the formation of a nanoporous aluminum oxide layer on a Si solar cell by the anodization process of Al thin films. The anodization process provided a template to transfer the nanopattern onto the Si surface. The small-sized nanoporous alumina template was attached to be covered on the textured surface and played the role of etching mask in the F-based dry etching process. Furthermore, we deposited an Al thin film onto the Si surface and the subsequent anodization process was performed. The alumina formulated on the deposited Al thin film did not show the array of nanoporous structure and no nanopatterns were transferred onto the surface. The large-areal alumina deposited on the Si surface showed enhanced photo-absorption in the ultraviolet spectral region of 243 nm, but increased the photo-reflectance in the visible and infrared spectral regions when compared to the Si-bare sample.     

A New Robust Watermark Embedding into Wavelet DC Components

In this paper, we propose a non‐blind watermarking method that embeds a pseudo‐random sequence (watermarks) into wavelet DC components. The DC area is not suitable for embedding because of severe visual degradation. We overcome the degradation problem by embedding watermarks into visually insensitive locations. We compare our experimental results with respect to JPEG compression with Cox's popular correlation‐based method. We also compare the robustness of our technique with other methods registered in CheckMark. This study reveals that the proposed method simultaneously provides good fidelity in quality as well as robustness against external attacks     

Effects of Pd(P) Thickness on the Microstructural Evolution Between Sn-3Ag-0.5Cu and Ni(P)/Pd(P)/Au Surface Finish During the Reflow Process

The microstructural evolution between Sn-3Ag-0.5Cu (SAC305) solder and Ni(P)/Pd(P)/Au finish during the reflow process was investigated for various Pd(P) thicknesses (0?μm to 0.6?μm). The reflow process was carried out in a belt-conveying reflow oven with peak temperature of 260°C. In the early stages of the reflow process, the Pd(P) layer either dissolved or spalled in the form of (Pd,Ni)Sn₄ into the molten solder, leaving behind an Ni₂SnP/Ni₃P bilayer on the Ni(P) layer. From the dissolution of the spalled (Pd,Ni)Sn₄ particles during the reflow process, the solubility of Pd in the molten SAC305 solder in the reflow process was estimated to be 0.18?wt.% to 0.25?wt.%. Regardless of the ratio of solder volume to pad opening size, the Ni₂SnP layer that formed in the early stage of reflow had a significant influence on the subsequent formation and growth of (Cu,Ni)₆Sn₅ at the solder interface. As the Ni₂SnP layer became thicker with increasing Pd(P) thickness, the formation of (Cu,Ni)₆Sn₅ became increasingly sluggish and occurred only at locations where the Ni₂SnP layer was locally thin or discontinuous, leading to a discontinuous morphology of (Cu,Ni)₆Sn₅. This was attributed to the Ni₂SnP layer that became an increasingly effective barrier to Ni diffusion with increasing thickness. Based on the experimental results, this study suggests detailed mechanisms underlying the effects of the Pd(P) thickness on the morphology and growth of the (Cu,Ni)₆Sn₅ formed during the reflow process.     

Growth of mane-like ZnS nanostructures by using a two-heating zone-tube furnace: structural characterization and photoluminescence

We have synthesized ZnS nanowires with mane-like branches by thermal evaporation of ZnS powder on the Au-coated Si(100) substrate using a two-heating zone tube furnace. The ZnS powder and the Si substrate were kept at 1,000 and 850 °C, respectively, in a nitrogen atmosphere during synthesis of the ZnS nanostructures. Field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and photoluminescence (PL) spectroscopy analyses were performed to investigate the structure, morphology and photoluminescence properties of the products. The axial nanowires grow along the [002] direction and have diameters of 100–200 nm, while on the other hand the branch nanowires grow along the [101] direction and their diameters and lengths are 30–50 and 800–100 nm, respectively. The room temperature PL spectrum with a Gaussian fitting exhibits two visible light emission bands centered at around 397 and 458 nm.