Patterned wafer inspection by high resolution spectral estimation techniques

A new self-reference signal processing technique is proposed for detecting the location of irregularities and defects in a periodic two-dimensional signal or image. Using high-resolution spectral estimation algorithms, the proposed technique first extracts the period and structure of repeated patterns from the image. Then a defect-free reference image for comparison with the actual image is produced. Since the technique acquires all the information needed from a single image (in contrast to most existing methods), there is no need for a database image, a scaling or alignment procedure or any a priori knowledge about the repetition period of the patterns.Potential application fields for the proposed method range from the area of wafer and mask defect inspection, which includes inspection of memory chips, shift registers, switched capacitors, CCD arrays, and LCD displays to other areas that deal with repeated structures, such as crystallography. Some results of applying the proposed technique to real images from microlithography are presented.     

A Quantitative Bacteria Monitoring and Killing Platform Based on Electron Transfer from Bacteria to a Semiconductor

A platform with both bacteria killing and sensing capabilities is crucial for monitoring the entire bacteria-related process on biomaterials and biomedical devices. Electron transfer (ET) between the bacteria and a Au-loaded semiconductor (ZnO) is observed to be the primary factor for effective bacteria sensing and fast bacteria killing. The electrons produce a saturation current that varies linearly with the bacteria number, semi-logarithmically, with R² of 0.98825, thus providing an excellent tool to count bacteria quantitatively in real-time. Furthermore, ET leads to continuous electron loss killing of about 80% of Escherichia coli in only 1 h without light. The modularity and extendability of this ET-based platform are also demonstrated by the excellent results obtained from other semiconductor/substrate systems and the stability is confirmed by recycling tests. The underlying mechanism for the dual functions is not due to conventional attributed Zn²⁺ leaching or photocatalysis but instead electrical interactions upon direct contact. The results reveal the capability of real-time detection of bacteria based on ET while providing information about the antibacterial behavior of ZnO-based materials especially in the early stage. The concept can be readily incorporated into the design of smart and miniaturized devices that can sense and kill bacteria simultaneously.     

Four decades of fuzzy sets theory in operations management: application of life-cycle,bibliometrics and content analysis

The blockchain is a technology which accumulates and compiles data into a chain of multiple blocks. Many blockchain researchers are adopting it in multiple areas. However, there are still lacks bibliometric reports exhibiting the exploration of an in-depth research pattern in blockchain. This paper aims to address that gap by analyzing the widespread of blockchain research activities conducted thus far. This study analyzed the Scopus database by using bibliometric analysis in a pool of more than 1000 articles that were published between 2013 and 2018. In particular, this paper discusses various aspects of blockchain research conducted by researchers globally. This study also focuses on the utilization of blockchain and its consensus algorithms. This bibliometric analysis discovered the following: (1) Blockchain able to solve security issues in internet of things (IoT) and would be an increasing trend in the future; (2) Researchers begin to adopt blockchain in healthcare area; (3) The most active country in blockchain publication is United States, followed by China and Germany; (4) Switzerland and Singapore are two small size countries that published few publications, however receives many citations. (5) Research collaborations between countries increased the research publications except for Canada, India, and Brazil. (6) Keyword analysis revealed that researchers are adopting blockchain to solve problems in multiple categories of the data research area (data privacy, digital storage, the security of data, big data, and distributed database). This study also highlighted the utilization and consensus of the algorithm in blockchain research.

     

Impact of compression molding conditions on the thermal and mechanical properties of polyethylene

Compression molding is a current technique in polymer processing. Despite numerous studies, effect of molding pressure on physical properties has surprisingly not been fully investigated. In this study, the thermal and mechanical behavior of the compression‐molded polyethylene were thus explored to better grasp the relationship between processing parameters and ensuing properties. The effect of the molding temperature, pressure, cooling rate, and temperature profile on the tensile and flexural moduli as well as melting point of polyethylene was studied. We conclude that higher tensile and flexural moduli are obtained by increasing pressure and molding temperature, as well as decreasing the cooling rate. Our results were corroborated by X‐ray diffraction and differential scanning calorimetry measurements. Moreover, the use of a temperature gradient with different temperatures for the upper and bottom plates of the mold leads to asymmetric samples whose tensile and flexural moduli are improved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46176.     

How is the capacity of ad hoc networks improved with directional antennas?

The capacity of wireless ad hoc networks is constrained by the interference caused by the neighboring nodes. Gupta and Kumar have shown that the throughput for such networks is only Θ bits per second per node in a unit area domain when omnidirectional antennas are used [1]. In this paper we investigate the capacity of ad hoc wireless networks using directional antennas. Using directional antennas reduces the interference area caused by each node, thus increases the capacity of the network. We will give an expression for the capacity gain and we argue that in the limit, when the beam-width goes to zero the wireless network behaves like the wired network. In our analysis we consider both arbitrary networks and random networks where nodes are assumed to be static. We have also analyzed hybrid beamform patterns that are a mix of omnidirectional/directional and a better model of real directional antennas. Simulations are conducted for validation of our analytical results. Su Yi received the B.S. and M.S degrees in automation from Tsinghua University, China, in 1998 and 2001, respectively. She received her Ph.D. degree in electrical engineering from Rensselaer Polytechnic Institute, in December 2005. Her research interests include various topics in wireless ad hoc networks, including capacity of wireless networks, error control coding, and multimedia communications over wireless. Yong Pei is currently a tenure-track assistant professor in the Computer Science and Engineering Department, Wright State University, Dayton, OH. Previously he was a visiting assistant professor in the Electrical and Computer Engineering Department, University of Miami, Coral Gables, FL. He received his B.S. degree in electrical power engineering from Tsinghua University, Beijing, in 1996, and M.S. and Ph.D. degrees in electrical engineering from Rensselaer Polytechnic Institute, Troy, NY, in 1999 and 2002, respectively. His research interests include information theory, wireless communication systems and networks, and image/video compression and communications. He is a member of IEEE and ACM. Shivkumar Kalyanaraman is an Associate Professor at the Department of Electrical, Computer and Systems Engineering at Rensselaer Polytechnic Institute in Troy, NY. He received a B.Tech degree from the Indian institute of Technology, Madras, India in July 1993, followed by M.S. and Ph.D. degrees in computer and Information Sciences at the Ohio State University in 1994 and 1997 respectively. His research interests are in network traffic management topics such as congestion control, reliability, connectionless traffic engineering, quality of service (QoS), last-mile community wireless networks, low-cost free-space-optical networks, automated network management using online simulation, multicast, multimedia networking, and performance analysis. His special interest lies in developing the interdisciplinary connections between network architecture and fields like control theory, economics, scalable simulation technologies, video compression and optoelectronics. He is a member of ACM and IEEE. Babak Azimi-Sadjadi received his B.Sc. from Sharif University of Technology in 1989, his M.Sc. from Tehran University in 1992, and his Ph.D. from the University of Maryland at College Park in 2001 all in Electrical Engineering. He is currently with Intelligent Automation Inc. where he is a Senior Research Scientist He also has a joint appointment with the department of Electrical, Systems, and Computer Engineering of Rensselaer Polytechnic Institute where he is a research assistant professor. His research interests include, nonlinear filtering, networked control systems, and wireless networks.     

Bulk electro-optic deflector-based switches

We propose two novel electro-optic (EO) deflectors based on two new nonrectangular geometries: the parabolic and the half-horn configurations. These devices not only provide excellent deflection angles, but also have the potential to build nonblocking 2 x 2 optical switches. A deflector figure of merit is defined, and comparisons with existing EO deflectors are given. Devices fabricated in LiTaO(3) demonstrate 3 dB of average insertion loss and 3 degrees deflection angles. These results represent the best deflection performances to our knowledge reported to date for bulk EO deflectors.     

Sorting ZnO particles of different shapes with low frequency AC electric fields

Separation of nanoparticles from a mixture of particles with different geometries by applying non-uniform AC electric field is investigated. For this propose, two morphologies of ZnO, rod and cubic shape, were synthesized in two separate processes. Then, they were mixed and dispersed in acetone and exposed to the electric field for being separated. It was found that combination of AC-electroosmosis which is present at low frequencies, and dielectrophoretic (DEP) force exerted on particles in non-uniform AC electric fields may yield to separation of particles based on their shape difference. This paper introduces an effective method for sorting and purification of nanoparticles after chemical synthesis based on their geometrical shape.     

A new technique for micro-patterning of nanoparticles on non-conductive substrate by low frequency AC electrophoresis

Electrophoretic deposition (EPD) has been known as a cost-effective and simple method in shaping or coating ceramic parts. Usefulness of this electrically driven method becomes more pronounced when it is applied for manipulating nanosize materials. Our findings in this area have showed that nanoparticle manipulation with EPD method is possible through applying low frequency alternating current (AC) electric fields. In our previous work, we explained how nanoparticles fill the non-conductive gap between two in-plane electrodes at frequency of 1 Hz. In this work, we used the similar idea to deposit TiO₂ nanoparticles on non-conductive Alumina base in direction parallel to the electrode edge. The length and width of TiO₂ deposited line was in the order of micrometer and coherency of deposited layer was good. It was concluded that with designing different electrode shapes, micro-patterning of ceramic nanoparticles on different substrates via low frequency AC electrophoretic deposition is possible.     

Effect of hydrothermal duration on synthesis of WO<Subscript>3</Subscript> nanorods

Among different type of transition metal oxides, tungsten trioxide (WO₃) is a suitable candidate for electronic device fabrication due to its n-type property and wide band gap. Herein, one-dimensional tungsten trioxide (WO₃) nanorods were achieved from an aqueous solution of sodium tungstate dihydrate (Na₂WO₄·2H₂O) and sodium chloride (NaCl) in an acidic media by a time-optimized hydrothermal synthesis in autoclave at 180°C or different synthesis durations. For studying morphology and size of obtained powder, X-ray diffraction (XRD), scanning electron microscope (SEM), and high resolution transmission electron microscope (HRTEM) were applied. Finally, WO₃ nanorods of about 2–3 μm in length and 100–200 nm in diameter were obtained during 3 h hydrothermal process.     

Graphene as an Electron Shuttle for Silver Deoxidation: Removing a Key Barrier to Plasmonics and Metamaterials for SERS in the Visible

The role of graphene in enabling deoxidation of silver nanostructures, thereby contributing to enhance plasmonic properties and to improve the temporal stability of graphene/silver hybrids for both general plasmonic and meta‐materials applications, as well as for surface enhanced Raman scattering (SERS) substrates, is demonstrated. The chemical mechanism occurring at the graphene–silver oxide interface is based on the reduction of silver oxide triggered by graphene that acts as a shuttle of electrons and as a kind of catalyst in the deoxidation. A mechanism is formulated, combining elements of electron transfer, role of defects in graphene, and electrochemical potentials of graphene, silver, and oxygen. Therefore, the formulated model represents a step forward from the simple view of graphene as barrier to oxygen diffusion proposed so far in literature. Single layer graphene grown by chemical vapor deposition is transferred onto silver thin films, a periodic silver fishnet structure fabricated by nanoimprint lithography, and onto silver nanoparticle ensembles supporting a localized surface plasmon resonance in the visible range. Through the study of these nanostructured graphene/Ag hybrids, the effectiveness of graphene in preventing and reducing oxidation of silver plasmonic structures, keeping silver in a metallic state over months at air exposure, is demonstrated. The enhanced and stable plasmonic properties of the silver‐fishnet/graphene hybrids are evaluated through their SERS response for detecting benzyl mercaptane.