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The description of events at the atomic level with computer memory restrictions and its application to the study of the accumulation and depletion of matter is discussed. Experiments involve the simulation of atom motion during electromigration by a Monte Carlo computer program. Two dimensions of current density were determined by the program. The utility of the model was demonstrated.

A compact, efficient electrical dual-circuit topology for the representation of transient thermal coupling is presented. Based on controlled sources, the method allows an arbitrary level of complexity to be used for each self and coupled response. Two possible variations on the circuit form, and the resulting requirements for model extraction, are developed. The method is applied to the modeling of transient thermal self-heating and coupling data for a pair of thermal sources representative of integrated device structures in semi-infinite homogeneous as well as trench-isolated substrates. [ABSTRACT FROM AUTHOR]

High-Q broadband passives are needed for monolithic microwave circuits in silicon. Coplanar waveguides (CPWs) provide an effective way to implement passives in silicon monolithic microwave integrated circuits. Silver "fat" wires in the backend interconnects, used for CPW fabrication, will reduce the bulk resistive loss in metallization to the lowest possible level, which is vital to minimize noise. Electromigration, electrochemical migration, and agglomeration issues are not a problem for silver microwave passives, because of their coarse dimensions and the low current densities encountered in these structures. In this letter, Ag and Cu CPWs were designed, fabricated and tested. Silver CPWs showed a 2-3 Ω/cm improvement in resistance over copper devices at 20 GHz. A circuit was identified in which the application of silver passives could provide an improvement in noise performance. [ABSTRACT FROM AUTHOR]

This article presents a novel and powerful goodness-of-fit test specifically designed for the Cauchy distribution. The motivation behind our research stems from the need for a more accurate and robust method to assess the fit of the Cauchy distribution to data. This distribution is known for its heavy tails and lack of finite moments. To compute the proposed test statistic, we utilize the maximum likelihood estimators of the unknown parameters, ensuring the test efficiency and reliability. In addition, Monte Carlo simulations are employed to obtain critical points of the test statistic for different sample sizes, enabling precise determination of the threshold for rejecting the null hypothesis. To assess the performance of the proposed test, we conduct power comparisons against several well-known competing tests, considering various alternative distributions. Through extensive simulations, we demonstrate the superiority of our test in the majority of the cases examined, highlighting its effectiveness in distinguishing departures from the Cauchy distribution. The contributions of our study are twofold. Firstly, we introduce a novel goodness-of-fit test tailored specifically for the Cauchy distribution, taking into account its unique characteristics. By incorporating the maximum likelihood estimate and employing Monte Carlo simulations, our test offers improved accuracy and robustness compared to existing methods. Furthermore, we provide practical validation of the proposed test through the analysis of a financial dataset. The application of the test to real-world data underscores its relevance and applicability in practical scenarios. [ABSTRACT FROM AUTHOR]

In this work, we report magnetic and optical anisotropies in tilted nickel (Ni) nanocolumns and their dependencies on the film growth conditions. The Ni nanocolumns were prepared using electron beam evaporation technique in conjunction with glancing angle deposition methodology. The film depositions were performed at various in-situ substrate temperatures viz. 30 °C, 150 °C, 250 °C and 300 °C. An increase in material density with in-situ substrate temperature due to the thermal diffusion mediated coalescence of neighbouring grains was observed. The results were further corroborated with the alterations in surface morphology of the films. The modification in tilt angle of the Ni nanocolumns was also observed with in-situ substrate heating due to the non-ballistic growth approach. The presence of uniaxial optical anisotropy was established in the films deposited at low substrate temperatures (< 250 °C) using generalized ellipsometry (GE). However, the uniaxial optical anisotropy was found to be negligible for the high temperature deposited films due to thermal diffusion effect. SQUID measurements were performed for quantification of magnetic anisotropy in the films. The estimated magnetic anisotropy energy confirmed low substrate temperature deposited films to be more anisotropic as compared to others. Magnetic coercivity of the films showed film porosity dependent changes in the field values. Overall, the present investigation demonstrates anisotropic behaviour of nanocolumnar nickel thin films for non-ballistic glancing angle deposition. [ABSTRACT FROM AUTHOR]

Self-cleaning surfaces have attracted much attention for the need to develop self-disinfected and hygienic surfaces. Surface wettability through nanomaterial fabrication has enticed the interest of researchers. The glancing angle deposition (GLAD) technique was implemented inside an electron-beam chamber to fabricate titanium oxide (TiO2) nanowire (NW) on n-type silicon (Si) substrate. Gold (Au) thin film (TF) was synthesized on top of bare TiO2 NW, and then the sample was annealed at 950 °C. The sample morphology was investigated using field emission scanning electron microscopy (FESEM), energy-dispersive analysis of X-rays (EDAX), high-resolution transmission electron microscopy (HR-TEM), and selective area diffraction (SAED) pattern analysis. The surface roughness of the samples was examined by high-resolution atomic force microscopy (HR-AFM) analysis. The photoluminescence (PL) spectrums were used to analyze the optical properties. The static contact angles of 113.2° and 41.2° were identified for the bare TiO2 NW and annealed TiO2 NW/Au TF samples, respectively. For 90 min, water contact angle was reduced from 113.2 to 82.5° for the bare TiO2 NW and from 41.2 to 14.2° for the annealed TiO2 NW/Au TF sample. The sliding angles of 17.53° and 38.1°, the maximum frictional forces of 11.8 μN and 24.19 μN, in addition with the work of adhesions of 43.64 mN/m and 126.17 mN/m have also been calculated for the bare TiO2 NW and annealed TiO2 NW/Au TF samples, respectively. The enhanced characteristics of the annealed TiO2 NW/Au TF samples indicate an excellent potential for the applications of smart tiles, anti-fogging, and self-cleaning surfaces. [ABSTRACT FROM AUTHOR]

Recently, it has been shown that the density based empirical likelihood concept extends and standardizes these methods, presenting a powerful approach for approximating optimal parametric likelihood ratio test statistics. In this article, we propose a density based empirical likelihood goodness of fit test for the Cauchy distribution. The properties of the test statistic are stated and the critical points are obtained. Power comparisons of the proposed test with some known competing tests are carried out via simulations. Our study shows that the proposed test is superior to the competitors in most of the considered cases and can confidently apply in practice. Finally, a financial data set is presented and analyzed. [ABSTRACT FROM AUTHOR]

We report the first fabrication of sputtered carbon, solid-phase microextraction (SPME) fibers. These fibers have competitive extraction capabilities compared with the commercial carbon wide range (CWR) SPME fiber. This report also includes a demonstration of a newly developed SPME test mix that includes 15 different compounds with a wide range of functional groups and chemical properties. The fiber fabrication process involves sputtering carbon onto fused silica fibers, and the effects of throw distance on the morphology of the carbon coatings were studied. Four different carbon coating thicknesses were evaluated, with PDMS added as a stationary phase. These fibers were characterized with multiple analytical techniques, including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) goniometry, as well as headspace (HS) and direct immersion (DI)–SPME–GC–MS. The best (11.5 µm) sputtered carbon SPME fibers, with and without PDMS, were evaluated using the new evaluation mix and compared with the commercial CWR fiber and a previously sputtered/developed silicon fiber. The new probe mix helped elucidate differences among the fibers, which would have been missed by current commercial test mixes. The sputtered carbon SPME fibers showed similar functional group selectivity as commercial CWR fibers. However, the sputtered carbon fibers showed higher responses per volume compared with the commercial CWR fiber, indicating the porous morphology of the sputtered carbon has the ability to overcome large phase thickness/volume discrepancies and increase the relative recovery for various compounds. [ABSTRACT FROM AUTHOR]

Optical prisms are made of glass and map temporal frequencies into spatial frequencies by decomposing incident white light into its constituent colors and refract them into different directions. Conventional prisms suffer from their volumetric bulky and heavy structure and their material parameters are dictated by the Lorentz reciprocity theorem. Considering various applications of prisms in wave engineering and their growing applications in the invisible spectrum and antenna applications, there is a demand for compact apparatuses that are capable of providing prism functionality in a reconfigurable manner, with a nonreciprocal/reciprocal response. Here, we propose a nonreciprocal metasurface-based prism constituted of an array of phase- and amplitude-gradient frequency-dependent spatially variant radiating super-cells. In conventional optical prisms, nonreciprocal devices and metamaterials, the spatial decomposition and nonreciprocity functions are fixed and noneditable. Here, we present a programmable metasurface integrated with amplifiers to realize controllable nonreciprocal spatial decomposition, where each frequency component of the incident polychromatic wave can be transmitted under an arbitrary and programmable angle of transmission with a desired transmission gain. Such a polychromatic metasurface prism is constituted of frequency-dependent spatially variant transistor-based phase shifters and amplifiers for the spatial decomposition of the wave components. Interesting features include three-dimensional prism functionality with programmable angles of refraction, power amplification, and directive and diverse radiation beams. Furthermore, the metasurface prism can be digitally controlled via a field- programmable gate array (FPGA), making the metasurface a suitable solution for radars, holography applications, and wireless telecommunication systems. [ABSTRACT FROM AUTHOR]

In this paper, the self-heating and mutual thermal coupling in a state-of-the-art SiGe:C multi-finger heterojunction bipolar transistor (HBT) was investigated in static dc operation conditions. Multi-finger HBT structure was created using Sentaurus structure editor with dimensions similar to the layout of SiGe:C multi-finger HBTs in ST-Microelectronics BiCMOS55 (B55) technology ( f > 300 GHz, f > 400 GHz) as per ST's BiCMOS55 process design kit guidelines. Three-dimensional thermal technology computer aided design (TCAD) simulations were carried out to obtain the temperature distribution in static dc operation. The lattice temperature ( T ) and heat flux ( F ) distribution inside the device were studied. The impact of back-end-of-line (BEOL) layers on static thermal behavior of the state-of-the-art SiGe:C multi finger HBTs was also investigated. The temperature dependent thermal resistance of different fingers of the trench isolated SiGe multi-finger HBT was extracted without and with back-end-of-line (BEOL) effect. An electro-thermal dc compact model of self-heating and mutual thermal coupling in multi-finger HBTs was proposed and applied to compare the modeling results with the TCAD simulation results. Very good agreement was achieved between results obtained from TCAD simulation and those obtained from compact model-based simulation. [ABSTRACT FROM AUTHOR]

The effect of Deep Trench Isolation (DTI) length and heat generation rate on the temperature distribution near the heat source region is investigated numerically for trench isolated devices. Computational results show that since trenches restrict to dissipate heat over the lateral sides, large temperature gradients are established in the trench isolated region which may deteriorate the performance of bipolar transistors. Sharp temperature gradients are more pronounced particularly at higher trench lengths and heat generation rates. [ABSTRACT FROM AUTHOR]

In this study, a numerical simulation method was employed to investigate and analyze superstructure fiber Bragg gratings (SFBGs) with five duty cycles (50%, 33.33%, 14.28%, 12.5%, and 10%). This study focuses on demonstrating the relevance between design period and spectral characteristics of SFBGs (in the form of graphics) for SFBGs of all duty cycles. Compared with complicated and hard-to-learn conventional coupled-mode theory, the result of the present study may assist beginner and expert designers in understanding the basic application aspects, optical characteristics, and design techniques of SFBGs, thereby indirectly lowering the physical concepts and mathematical skills required for entering the design field. To effectively improve the accuracy of overall computational performance and numerical calculations and to shorten the gap between simulation results and actual production, this study integrated a perfectly matched layer (PML), perfectly reflecting boundary (PRB), object meshing method (OMM), and boundary meshing method (BMM) into the finite element method (FEM) and eigenmode expansion method (EEM). The integrated method enables designers to easily and flexibly design optical fiber communication systems that conform to the specific spectral characteristic by using the simulation data in this paper, which includes bandwidth, number of channels, and band gap size. [ABSTRACT FROM AUTHOR]

We propose a new scheme of stretchable metal interconnects utilizing the electroplated three-dimensional (3D) coil structure, as a strategy for improving the stretching performance of spring-like electrodes through the suppression of local stress concentration. In this process, the 3D copper coils are fabricated by a multi-step electroplating process, and embedded within an elastomeric substrate forming stretchable configuration. By comparing the stretching behavior of the two-dimensional and 3D coils under static or cyclic deformation, the beneficial effects of the 3D configuration have been demonstrated. The present technique can be regarded as an effective way to enhance the stability of interconnects under cyclic deformation significantly, while maintaining the high mechanical strength and electrical conductivity of electroplated electrodes. [ABSTRACT FROM AUTHOR]

Ferrum of BCC crystal structure is a typical kind of matrix in structural alloy steels which could be strengthened by introducing some second phase. In the present study, BCC Fe thin films with hafnium oxide (HfO2) second phase have been synthesized in an electron beam evaporation system. Multi-layered and glancing angle deposition (GLAD) techniques were taken to form some HfO2 second phase in Fe films. Ion irradiation was conducted to investigate the irradiation resistance of the obtained samples with and without HfO2 second phase. [ABSTRACT FROM AUTHOR]

Glancing angle deposition (GLAD) is a physical vapour deposition method used to fabricate highly functional thin films with an engineerable columnar morphology. Recent developments in GLAD technology have produced columnar nanostructures of increased complexity, including periodic, nanofibrous, perforated, and graded porosity thin films for use in applications ranging from sensors and actuators to optical filters, microfluidics, and catalysis. A brief review of GLAD methodology and historical developments is followed by a discussion of the latest developments in this field. [ABSTRACT FROM AUTHOR]

Metasurfaces are thin two-dimensional metamaterial layers that allow or inhibit the propagation of electromagnetic waves in desired directions. For example, metasurfaces have been demonstrated to produce unusual scattering properties of incident plane waves or to guide and modulate surface waves to obtain desired radiation properties. These properties have been employed, for example, to create innovative wireless receivers and transmitters. In addition, metasurfaces have recently been proposed to confine electromagnetic waves, thereby avoiding undesired leakage of energy and increasing the overall efficiency of electromagnetic instruments and devices. The main advantages of metasurfaces with respect to the existing conventional technology include their low cost, low level of absorption in comparison with bulky metamaterials, and easy integration due to their thin profile. Due to these advantages, they are promising candidates for real-world solutions to overcome the challenges posed by the next generation of transmitters and receivers of future high-rate communication systems that require highly precise and efficient antennas, sensors, active components, filters, and integrated technologies. This Roadmap is aimed at binding together the experiences of prominent researchers in the field of metasurfaces, from which explanations for the physics behind the extraordinary properties of these structures shall be provided from viewpoints of diverse theoretical backgrounds. Other goals of this endeavour are to underline the advantages and limitations of metasurfaces, as well as to lay out guidelines for their use in present and future electromagnetic devices. This Roadmap is divided into five sections: 1. Metasurface based antennas. In the last few years, metasurfaces have shown possibilities for advanced manipulations of electromagnetic waves, opening new frontiers in the design of antennas. In this section, the authors explain how metasurfaces can be employed to tailor the radiation properties of antennas, their remarkable advantages in comparison with conventional antennas, and the future challenges to be solved. 2. Optical metasurfaces. Although many of the present demonstrators operate in the microwave regime, due either to the reduced cost of manufacturing and testing or to satisfy the interest of the communications or aerospace industries, part of the potential use of metasurfaces is found in the optical regime. In this section, the authors summarize the classical applications and explain new possibilities for optical metasurfaces, such as the generation of superoscillatory fields and energy harvesters. 3. Reconfigurable and active metasurfaces. Dynamic metasurfaces are promising new platforms for 5G communications, remote sensing and radar applications. By the insertion of active elements, metasurfaces can break the fundamental limitations of passive and static systems. In this section, we have contributions that describe the challenges and potential uses of active components in metasurfaces, including new studies on non-Foster, parity-time symmetric, and non-reciprocal metasurfaces. 4. Metasurfaces with higher symmetries. Recent studies have demonstrated that the properties of metasurfaces are influenced by the symmetries of their constituent elements. Therefore, by controlling the properties of these constitutive elements and their arrangement, one can control the way in which the waves interact with the metasurface. In this section, the authors analyze the possibilities of combining more than one layer of metasurface, creating a higher symmetry, increasing the operational bandwidth of flat lenses, or producing cost-effective electromagnetic bandgaps. 5. Numerical and analytical modelling of metasurfaces. In most occasions, metasurfaces are electrically large objects, which cannot be simulated with conventional software. Modelling tools that allow the engineering of the metasurface properties to get the desired response are essential in the design of practical electromagnetic devices. This section includes the recent advances and future challenges in three groups of techniques that are broadly used to analyze and synthesize metasurfaces: circuit models, analytical solutions and computational methods. [ABSTRACT FROM AUTHOR]

Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii–Moriya-like interaction. As a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. These recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review. [ABSTRACT FROM AUTHOR]

A non-linear numerical finite element method model of a thermo-electric focal plane array detector is presented here. Laser induced thermo-voltage profiles tend to spread out for small lock-in frequencies as the thermal diffusion length is inversely proportional to the square-root of the lock-in frequency. This leads to a frequency and spatial dependent thermal cross-talk level. In this paper we investigate the thermal cross-talk level quantitatively as a function of spatial coordinates and lock-in frequency. Experimental data are provided at an optical power level of 1 W. The impact of non-linear thermal parameters as the temperature dependence of the absorption coefficient, the thermal conductivity, the heat transfer coefficient and the Seebeck coefficient on the thermal profile and cross-talk level generated inside the detector material is studied in detail. Heat losses that are included in the model are conduction and laminar free convection. The relative importance of the above-mentioned non-linear thermal parameters in terms of thermal cross-talk for steady-state solutions is discussed as well. [ABSTRACT FROM AUTHOR]