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This work presents a vertical hyperbolic metamaterial (vHMM) consisting of a vertically stacked metal-dielectric multilayer that operates in the visible spectrum. The vHMM is designed by exploiting the relation between negative refraction and effective permittivity along the perpendicular direction of the layers (ε ⊥). When a vHMM has a high loss tangent defined by tan δ ⊥ ≡ Im(ε ⊥)/Re(ε ⊥), even a vHMM composed of relatively thick layers can generate negative refraction. A fabricable vHMM composed of gold and copolymer resist (EL8) which exhibits negative refraction at the wavelengths between 450 and 550 nm is designed using critical layer thickness analysis. The largest negative refraction is observed at the wavelength of 500 nm, where the angle of refraction reaches −1.03°. The corresponding loss tangent and equivalent refractive index are 1.08 and −0.47, respectively. However, negative refraction is not observed at the wavelengths longer than 550 nm due to low tan δ ⊥. We uncover that the tan δ ⊥ of a vHMM is the dominant condition for generating negative refraction rather than the ratio of layer thickness to wavelength.

The emphasis of biocompatible polymer applications in medical sciences and biotechnology has remarkably increased. Developing new low-cost, low-toxicity and lightweight composite forms of biopolymers has become even more attractive since the addition of new species into polymer matrices assist to improve biomedical activities of such materials to a higher extend. Developments in nanoscience and nanotechnology recently contribute to controlled fabrication and ultraprecise diagnosis of such materials. This study concerns the observation of solution processing effects in the fabrication of porous PLA/AGNWs bionanocomposite coatings using electron and ion processing based serial cross-sectioning and high-resolution imaging. The nanostructuring and characterization were both performed in a focused ion-beam-scanning electron microscope (FIB-SEM) platform. HR-SEM imaging was conducted on-site to track solvent based morphological property alterations of PLA and PLA/AgNWs structures. Simultaneous SEM-EDS analyses revealed the elemental distribution and the chemical composition along the cross-sectioned regions of the samples. Accordingly, it was observed that, in case of acetone dissolved materials, both pristine PLA and PLA/AgNWs samples sustained their foamy structure. When chloroform was used as the solvent, the porosity of the polymer matrices was less and the resulting structure was found to be denser than samples dissolved in acetone with a lower surface area ratio inside the material. This can be attributed to the rapid volatilization of acetone compared to chloroform, and hence the formation of interconnected pore network. For both nanocomposite biopolymers dissolved in acetone and chloroform, silver nanowires were homogeneously distributed throughout PLA matrices. [ABSTRACT FROM AUTHOR]

Commercial gallium nitride (GaN) high-electron-mobility transistors used for power electronics applications show superior performance compared to silicon (Si)-based transistors. Combined with an increased radiation hardening properties, they are key candidates for high-performance power systems in a harsh environment, such as space. However, for this purpose, it is key to know the potential failure mechanisms (FMs) of the devices in depth. Here, we demonstrate how the repeated thermomechanical stress in a power cycling (PC) test within specified operating conditions destroys the GaN device. Based on leakage current localization analysis, we identify an FM with a yet unknown root cause. Utilizing emission microscopy, focused ion beam cutting, and scanning electron microscope techniques, it is revealed that multilayer cracks of a GaN die are triggered by a commercial leading package structure, which shows excellent capability under frequent thermomechanical stress. Through multiphysics simulations, it is shown that the structural factors that lie behind the strong performing component properties inside the package ultimately are directly related to the failure pattern. This article is accompanied by a video demonstrating dynamic thermal distribution difference between thermography measured in a practical experiment and a multiphysics simulation result during a single PC of a PC test. This article is accompanied by a supplementary figures file demonstrating test environment, preparation process of specimens, and reverse engineering results for the simulation model. [ABSTRACT FROM AUTHOR]

Today's (nano)-functional materials, usually exhibiting complex physical properties require local investigation with different microscopy techniques covering different physical aspects such as dipolar andmagnetic structure. However, often these must be employed on the very same sample position to be able to truly correlate those different information and corresponding properties. This can be very challenging if not impossible especially when samples lack prominent features for orientation. Here, we present a simple but effective method to mark hundreds of approximately 15×15 μm sample areas at one time by using a commercial transmission electronmicroscopy grid as shadow mask in combination with thin-film deposition. Areas can be easily distinguished when using a reference or finder grid structure as shadow mask. We show that the method is suitable to combine many techniques such as light microscopy, scanning probe microscopy and scanning electron microscopy. Furthermore, we find that best results are achieved when depositing aluminium on a flat sample surface using electron-beam evaporation which ensures good line-ofsight deposition. This inexpensive high-throughput method has several advantageous over other marking techniques such as focusedion-beam processing especially when batch processing or marking of many areas is required. Nevertheless, the technique could be particularly valuable, when used in junction with, for example focused ion-beam sectioning to obtain a thin lamellar of a particular pre-selected area. [ABSTRACT FROM AUTHOR]

Abstract: Based on the combined milling-imaging capabilities of focused ion-beam equipment, a novel approach of measuring residual stress of interconnects by slot milling and geometric phase analysis is presented. This method is performed through measuring the displacement field perpendicular to the slot due to the stress release by geometric phase analysis, and then solving the residual stress along the interconnect line by finite element method. Grating fabrication, slot milling and micrographs capturing are implemented in focused ion-beam equipment. The displacement at the edge of the slot and the residual stress of a copper interconnect line were found to be in the range 26–45nm and 265–467MPa, respectively. This work provides an effective way to determine the residual stress of film lines. [ABSTRACT FROM AUTHOR]

Abstract: Anodized aluminium oxide (AAO) fabricated by electrochemical anodization of aluminium is used as the substrate for focused ion-beam (FIB) fabrication of single nanopore and nanopore arrays. The method is based on the controlled and selective removal of AAO barrier oxide film by FIB milling. FIB process with different milling conditions is applied to open single nanopores (diameter of 60 nm) or circular nanopore arrays with a different number of opened pores on AAO substrate. This process combines a low cost AAO substrate and FIB milling, and offers an economically viable alternative for the fabrication of nanopore devices with controlled dimensions for a range of applications in nanofluidics, molecular separations and biosensing. [Copyright &y& Elsevier]

Abstract: To aid investigation of formation processes and/or adhesiveness properties, microstructures of the interface between diamond-like carbon (DLC) film produced by focused ion-beam chemical vapor deposition method and crystalline Si substrate were analyzed by high-resolution transmission electron microscopy (HRTEM) in detail. Bright field images showed that a transition layer existed at the DLC/Si interface. From EDS analysis, it was found that the transition layer consisted of both C and Si atoms and their concentrations varied continuously along growth direction over about 100 nm. In addition, HRTEM image and convergence beam electron diffraction pattern revealed that the transition layer was divided structurally into three layers, i.e., amorphous, clustered and crystalline Si–C layers. [Copyright &y& Elsevier]

Flip chip reliability was evaluated using thermal stress tests at 150 °C. Electrical failures of flip chip devices were found to occur at the solder/under-bump-metallization interface by forming a porous amorphous chromium layer. The formation of the porous amorphous layer responsible for electrical failures resulted from the outdiffusion of copper atoms from a copper–chromium co-deposit, used as one of the under-bump-metallization layers. A strong interaction of Cu with the Sn component of the solder is the driving force of the Cu outdiffusion. [Copyright &y& Elsevier]

A brief overview of the transmission electron microscope (TEM) operation in the semiconductor industry is given. A recent emergence of a focused ion-beam (FIB) machine as a dedicated TEM specimen preparation tool has changed the role of TEM in the semiconductor industry dramatically. Advantages and disadvantages of TEM specimens prepared by a FIB machine are discussed together with damage produced by high-energy ion beams. [Copyright &y& Elsevier]