Plan-view transmission electron microscopy (TEM) or electron diffraction imaging of a bulk or 2D material can provide detailed information about the structural or atomic arrangement in the material. A systematic and easily implementable approach to preparing site-specific plan-view TEM samples for 2D thin film materials using FIB is discussed that could be routinely used. The methodology has been successfully applied to prepare samples from 2D materials such as, MoS2 thin film, vertically oriented graphene film (VG), as well as heterostructure material SnTiS3. It is worth mentioning that in contrast to planar conventional graphene, VG grows vertically from the substrate and takes nanosheet arrays. Samples prepared using this methodology provide a simple, faster, and precise course in obtaining valuable structural information. The top-view imaging offers various information about the growth nature of the materials suggesting the efficiency of the sample preparation process.

Focused ion beam (FIB) technology has become a promising technique in micro- and nano-prototyping due to several advantages over its counterparts such as direct (maskless) processing, sub-10 nm feature size, and high reproducibility. Moreover, FIB machining can be effectively implemented on both conventional planar substrates and unconventional curved surfaces such as optical fibers, which are popular as an effective medium for telecommunications. Optical fibers have also been widely used as intrinsically light-coupled substrates to create a wide variety of compact fiber-optic devices by FIB milling diverse micro- and nanostructures onto the fiber surface (endfacet or outer cladding). In this paper, the broad applications of the FIB technology in optical fibers are reviewed. After an introduction to the technology, incorporating the FIB system and its basic operating modes, a brief overview of the lab-on-fiber technology is presented. Furthermore, the typical and most recent applications of the FIB machining in optical fibers for various applications are summarized. Finally, the reviewed work is concluded by suggesting the possible future directions for improving the micro- and nanomachining capabilities of the FIB technology in optical fibers.

In this work, we study and characterize the layout-induced device strain and its impact on RF performance of 22-nm-ultrathin body and buried oxide fully depleted silicon-on-insulator (UTBB FDSOI) P-channel field-effect transistor (PFET). This will help in boosting and optimizing the RF performance for the targeted application. With shrinking device dimensions, conventional stress liners and embedded stressors used in strain-engineered CMOS devices become less effective. Therefore, intrinsically strained materials, such as compressively strained SiGe, are widely used to boost the holes' mobility in the channel. The stress level depends on both the manufacturing process and device geometry, and the optimization of these leads to improved dc and RF performances of PFET devices. We hereby study various layout parameters, such as width and length of the active region, contacted poly pitch, number of fingers, and source/drain contact, to maximize the channel uniaxial strain parallel to the current flow direction and, thus, improve the electrical performances. The studied layout parameters are then applied on sliced-active (RX) structures, which enables to achieve up to 30% improvement of both f T and f MAX parameters of SiGe PFET with respect to a reference device. This also allows reducing the parasitic capacitance without significantly degrading the dc performance. The device strain modeling and physical characterization were conducted through the finite-element method (FEM) and nanobeam electron diffraction (NBED) in the transmission electron microscopy (TEM), respectively.

The usage of heterostructures of ferromagnetic and ferroelectric materials, as a means of achieving magnetoelectric multiferroic coupling, is a widely used approach which has been showing promising results. Along this line of thought, the deposition of BaTiO3 and Fe multilayers on LaAlO3, MgO, Al2O3 and SrTiO3 substrates using RF-magnetron sputtering was carried out to study its viability to produce magnetoelectric heterostructures. It is shown that each substrate constrains the growth of the deposited thin films, even for the same deposition conditions. This is clearly seen through the magnetic properties of the thin film, mainly after performing a 900 degrees C thermal annealing in air. The thermal annealing results in the creation of iron oxides specific of each one of the substrates where the deposition took place. (c) 2020 Elsevier B.V. All rights reserved.

Focused ion beam (FIB) milling is widely used in fields such as the semiconductor industry and materials science research. The direct writing and small feature size also make FIB milling attractive for rapid prototyping of novel photonic structures. In this manuscript, we describe in detail a FIB milling procedure which enables high-resolution fabrication of complex micro- and nanostructures with precise geometry control. Two different procedures (for 2D and 3D structures) are described and implemented on the tip of a glass optical fiber for fabricating diverse structures embedded on or below the tip surface. The procedures described here can be easily adjusted and implemented on any conductive or non-conductive substrate.

In this paper, we investigate the mode sensitivity (S-mode) of subwavelength grating slot (SWGS) waveguides. S-mode is an important parameter in various waveguide-based photonic circuits such as sensors, modulators, and thermally-controlled devices. It is a measure of the sensitivity of the waveguide effective index towards the refractive index perturbations in the cladding medium. The SWGS waveguide exhibits high mode sensitivity, as it combines sensitivity enhancement features of both slot and subwavelength grating waveguides. Finite-difference time-domain simulations are performed for the analysis, design, and optimization of the hybrid structure. The SWGS waveguide is incorporated into a Mach-Zehnder interferometer and fabricated on a silicon-on-insulator platform for the experimental estimation of S-mode. The measured S-mode value of 79% is consistent with the theoretical prediction of 83%.

We report on numerical simulations and fabrication of an optical fiber plasmonic lens for near-field focusing applications. The plasmonic lens consists of an Archimedean spiral structure etched through a 100 nm-thick Au layer on the tip of a single-mode SM600 optical fiber operating at a wavelength of 632 : 8 nm. Three-dimensional finite-difference time-domain computations show that the relative electric field intensity of the focused spot increases 2 : 1 times when the number of turns increases from 2 to 12. Furthermore, a reduction of the intensity is observed when the initial inner radius is increased. The optimized plasmonic lens focuses light into a spot with a full-width at half-maximum of 182 nm, beyond the diffraction limit. The lens was fabricated by focused ion beam milling, with a 200nm slit width.

Vertically aligned graphene nanosheet arrays (VAGNAs) exhibit large surface area, excellent electron transport properties, outstanding mechanical strength, high chemical stability, and enhanced electrochemical activity, which makes them highly promising for application in supercapacitors, batteries, fuel cell catalysts, etc. It is shown that VAGNAs terminated with a high-quality single-layer graphene sheet, can be directly grown on germanium by plasma-enhanced chemical vapor deposition without an additional catalyst at low temperature, which is confirmed by high-resolution transmission electron microscopy and large-scale Raman mapping. The uniform, centimeter-scale VAGNAs can be used as a surface-enhanced Raman spectroscopy substrate providing evidence of enhanced sensitivity for rhodamine detection down to 1 x 10(-6) mol L-1 due to the existed abundant single-layer graphene edges. (C) 2019 Elsevier Ltd. All rights reserved.

This work demonstrates an approach for simplifying fiber-to-chip (edge coupling) packaging by virtually eliminating the longitudinal alignment procedure (also increasing compactness and efficiency) through a fiber lens embedded into the structure of the fiber itself. A parabolic lens, fabricated using focused ion beam milling, with a diameter of 15 mu m and height of 5 mu m, was embedded 6.5 mu m (the working distance of the parabolic lens) below the endfacet of the fiber. The lens focuses a 10.4 mu m fiber mode into a spot size of 2.6 mu m on the surface of an SMF-28e single-mode optical fiber. The properties of the fabricated lens were studied using the three-dimensional finite-difference time-domain numerical method, and the optimal parameters for maximizing the coupling conditions were extracted. The conversion loss of the lens is estimated to be around 0.5dB. The insertion loss and lateral alignment of the proposed parabolic lens is comparable to a commercial lensed fiber, while directly ensuring the longitudinal alignment, easing the angular alignment, and providing additional mechanical and environmental robustness.

We experimentally demonstrate a slotted subwavelength grating (SSWG) waveguide on a silicon-on-insulator platform. The waveguide was included in an asymmetric Mach-Zehnder interferometer, and a fluid sensing experiment was performed. The estimated mode sensitivity (79 %) is consistent with the simulation results (83 %). The high mode sensitivity of the SSWG waveguide makes it suitable for compact integrated optofluidic sensors.

The wetting behavior of homogeneous systems is now well understood at the macroscopic scale. However, this understanding offers little predictive power regarding wettability when mesoscopic chemical and morphological heterogeneities come into play. The fundamental interest in the effect of heterogeneity on wettability is derived from its high technological relevance in several industries, including the petroleum industry where wettability is recognized as a key determinant of the overall efficiency of the water-flooding-based enhanced oil recovery process. Here, we demonstrate the use of the atomic force microscopy force curve measurements to distinguish the roles of chemistry and morphology in the wetting properties of rock formations, thus providing a clear interpretation and deeper insight into the wetting behavior of heterogeneous formations. Density functional theory calculations further prove the versatility of our approach by establishing benchmarks on ideal surfaces that differ in chemistry and morphology in a predefined manner.

A gradient-index optical fiber lens is proposed and fabricated on the tip of a single-mode fiber using focused ion beam milling. Second-order effective medium theory is used to design a gradual change in the fill factor, which ensures a parabolic effective refractive index distribution. The proposed fiber lens design is simulated via the three-dimensional finite-difference time-domain method, and demonstrated through confocal optical measurements. At a wavelength of 1550 nm, the fabricated lenses focus a 10.4 μm mode field diameter exiting the fiber into spot sizes between 3-5 μm, located 4-6 μm away from the fiber tip. Direct coupling into a silicon-on-insulator chip is also demonstrated, where the fabricated gradient-index lens has a coupling efficiency comparable to a commercial lensed fiber.

Efficient edge coupling into a silicon waveguide is demonstrated using an optical fiber axicon lens operating at 1550 nm. The axicon was fabricated on the cleaved endfacet of an SMF-28e optical fiber using a focused ion beam milling process. The lens converts the guided mode of the optical fiber (mode field diameter of 10.4 μm) into a Bessel-type beam with an extended depth of focus, which was verified both experimentally and by three-dimensional finite-difference time-domain simulations. Axicon lenses with a diameter of 15 μm and heights of 3.5 and 5.0 μm were fabricated, and their focusing effect optically characterized through high-resolution confocal imaging, showing a focal spot size of 3.57 and 2.34 μm, respectively. The coupling efficiency from the axicon into a silicon-on-insulator photonic integrated circuit is comparable to that of a commercial tapered lensed fiber, and in some cases slightly higher. Due to the extended depth of focus, the axicon lens also offers a larger alignment tolerance in the longitudinal direction.

We fabricate a gradient-index lens on the end facet of an optical fiber by focused ion beam. At 1550 nm, the lens generates a 2.2 μm spot at a working distance of 4.2 μm. This lens can be used for efficient edge-coupling into optical chip.

Methods of CMOS resistance process voltage temperature variation detection and compensation are described. Two different approaches are proposed and comparative analysis is performed. The first solution makes use of an external precise resistor as a variation reference, while the second one uses reference clock frequency for the same purpose. Detection of variations is realized using the proposed digital and analog solutions. Efficiency of the suggested methods are tested and presented for high-speed CMOS systems.