Top Substrate Research Articles

Improving Short Channel Effects by Reformed U-Channel UTBB FD SOI MOSFET: A Feasible Scaled Device

U-channel ultra-thin body and buried oxide (U-UTBB) Silicon On Insulator (SOI) Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) present unique features which are simple, high-performance, area efficient, and compatible with CMOS technology. In this paper, we present the electrical characteristics of a U-UTBB SOI MOSFET with reforming the U-channel. This proposed symmetrical and planar device is initiated by removing two spacers around the recessed metal gate in the U-channel MOSFET. Hence, it causes to increase the overall channel length at the firm metal gate space along with saving area. As it has confirmed by two-dimensional and two-carrier device simulation results, the proposed structure which is termed Reformed U-UTBB (R-U-UTBB) fully depleted SOI MOSFET exhibits advantages in the device performance focusing on short channel effects (SCEs) factors including the sub-threshold slope, the drain induced barrier lowering (DIBL), and the threshold voltage roll-off. Leakage current and on-to-off current ratio are studied as well which all of them show the superiority of proposed structure compared with the U-UTBB FD SOI MOSFET and a conventional UTBB (C-UTBB) FD SOI MOSFET. In addition, the effects of process-induced variations have investigated by varying buried oxide thickness, top silicon thickness, channel thickness, substrate doping, and oxide thickness on threshold voltage, sub-threshold slope, and drain induced barrier lowering (DIBL).

Wideband Printed Half Bow-Tie Antenna Array Based on a Quad-Mode Reconfigurable Feeding Network for UAV Communications

In this article, a wideband printed half bow-tie antenna array based on a quad-mode reconfigurable feeding network for unmanned aerial vehicle (UAV) communications is presented. The proposed array consists of four printed half bow-tie antennas in the top substrate, two supports with a tapered balun, and a reflector with the reconfigurable feeding network in the bottom substrate. For UAV communications caused by wide beam coverage, the proposed reconfigurable feeding network using one single-pole-four-throw (SP4T) and two single-pole-three-throw (SP3T) switches can adjust the phase and amplitude to the antenna element. By controlling the switches, the proposed array can be operated on four linear polarization modes. The simulated and measured results prove the proposed array reconfigurability of the main beam in four directions with 45° steps in the azimuth plane. In addition, the proposed array achieves the wide 10-dB impedance bandwidth of approximately 29.6% (1507 MHz) from 4.1 to 5.6 GHz. The peak gain and half-power beamwidths (HPBWs) on azimuth and elevation planes of the proposed array are approximately 5.9 dBi, 240°, and 99°, respectively. The overall volume size of the proposed array is $60\times 60\times18.3$ mm3 ( $\sim \lambda _{0}\times \lambda _{0}\times 0.3\lambda _{0}$ at 5.1 GHz).

Diversifying grain orientation and expediting 10 μm Cu/Sn/Cu TLP bonding process with Ni doping

Prolonged bonding time and the excess thermal stress have been the bottleneck for transient liquid-phase (TLP) bonding in heterogeneous integration. To alleviate such issues, adequate amount of Ni was added to the Sn-3.0Ag-0.5Cu (SAC305) solder. With addition of Ni, the time elapsed for complete TLP bonding was shortened significantly. The distinct correlation between intermetallic compounds (IMCs) morphology and Ni content was investigated on both top and bottom substrates. Moreover, the effect of Ni on diversification of grain orientation of IMCs was also quantified by electron backscatter diffraction (EBSD). Also, Ni doping in TLP bonding provided smaller grain sizes. The mechanical strength of the TLP interconnection is therefore expected to be enhanced by Ni doping in solder.

Triangulated Cylinder Origami-Based Piezoelectric/Triboelectric Hybrid Generator to Harvest Coupled Axial and Rotational Motion.

Piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs) are representative technologies that can harvest mechanical energy. In general, piezoelectric/triboelectric hybrid generators can harvest considerable energy with a limited input; however, PENGs and TENGs entail different requirements for harvesting energy. Specifically, PENGs produce a large output when a large mechanical strain is applied, and TENGs require a large surface area to produce a high power. Therefore, it is necessary to develop an innovative strategy in terms of the structural design to satisfy the requirements of both PENGs and TENGs. In this study, we developed a triangulated cylinder origami-based piezoelectric/triboelectric hybrid generator (TCO-HG) with an origami structure to enable effective energy harvesting. The proposed structure consists of a vertical contact-separation TENG on the surface of the triangulated cylinder, PENG on the inner hinge, and rotational TENG on the top substrate to harvest mechanical energy from each motion. Each generator could produce a separate electrical output with a single input. The TCO-HG could charge a 22 μF commercial capacitor and power 60 LEDs when operated.

On-Chip Antenna Design Using the Concepts of Metamaterial and SIW Principles Applicable to Terahertz Integrated Circuits Operating over 0.6–0.622 THz

This research work presents the investigation of realizing an on-chip antenna based on the metamaterial concept, which is working over the terahertz (THz) band for applications in integrated circuits. The proposed on-chip antenna is constructed of five stacked layers of polyimide and aluminum as top and bottom substrates, radiation patches, ground plane, and feed line. The four square-shaped radiation patches are implemented on the 50 μ m top-polyimide substrate, and the feed line is realized on the 50 μ m bottom-polyimide layer by designing the simple square microstrip lines, which are all connected to each other and then excited by waveguide port. The ground plane including a coupling square slot has sandwiched between the top- and bottom-polyimide layers. The coupling square slot etched on the ground plane is exactly placed under the patch to optimum transfer the electromagnetic signal from the bottom feed line to the top radiation patch. To achieve high performance parameters without increasing the antenna's physical dimensions, the metamaterial and substrate integrated waveguide properties have been applied to the antenna structure by implementing linear tapered slots on the patch top surfaces and metallic via holes throughout the middle ground plane connecting top and bottom substrates to each other. The slots play the role of series left-handed (LH) capacitors (CL) and the via holes act as shunt LH inductors (LL). The overall dimension of the proposed metamaterial-based on-chip antenna is 1000 × 1000 × 100 μm3. This antenna can cover the frequency band from 0.6 THz to 0.622 THz, which is equal to 20 GHz bandwidth. The radiation gain and efficiency across the operating frequency band varies from 1.1 dBi to 1.8 dBi, and from 58% to 60.5%, respectively. The results confirm that the proposed on-chip antenna with compact dimensions, wide bandwidth over the terahertz domain, low profile, cost effective, simple configuration, and easy to manufacture can be potentially appropriate for terahertz integrated circuits.

A Double-Deck Self-Digitization Microfluidic Chip for Digital PCR.

In this work, a double-deck microfluidic chip was presented for digital PCR application. This chip consists of two reverse-placed micro-patterned polydimethylsiloxane (PDMS) layers between the top and bottom glass substrates. Each micropatterned PDMS layer contains more than 20,000 cylindrical micro-chambers to hold the partitioned droplets. The double-deck designs can double the number of chambers and reagent capacity without changing the planar area of the chip. In addition, carbon black was mixed into the pure PDMS gel to obstruct the passage of fluorescence from the positive chambers between the two layers of the chip. Thus, the fluorescence signal of micro-chambers in different layers of the chip after PCR can be collected without mutual interference. The quantitative capability of the proposed chip was evaluated by measuring a 10-fold serial dilution of the DNA template. A high accuracy of the absolute quantification for nucleic acid with a dynamic range of 105 was demonstrated by this chip in this work. Owing to its characteristics of small planar area, large capacity, and sensitivity, the double-deck microfluidic chip is expected to further promote the extensive applications of digital PCR.

Liquid-Crystal-Embedded Aperture-Coupled Microstrip Antenna for 5G Applications

This letter presents a novel reconfigurable microstrip antenna with a frequency of 28 GHz and an embedded liquid crystal (LC). First, a novel fabrication process that employs a heat press machine is developed. This allows for the successful creation of thin substrates with thicknesses ranging between 0.13 and 0.25 mm. It is validated that the proposed stacked topology achieves a wide tunable range of resonant frequency. In addition, a simple bias configuration is achieved by connecting the bias position to the middle of the patch, where radio frequency (RF) potential is zero. The proposed antenna adopts a three-layer stacked printed circuit board (PCB) structure to render a cavity in which the LC is injected. The bottom patch of the top substrate is designed to contact the LC, and thus, it simultaneously functions as a dc bias electrode and a radiating element. In addition, unlike conventional stacked patch antennas, the additional patch on the top of the PCB structure is tuned to enhance gain. Compared with the simulated performance of a prior LC-based antenna, the tunable range of the resonant frequency of the proposed antenna is improved by more than three times at a center frequency of 28 GHz and the peak radiation efficiency is improved by up to 17%. Furthermore, the area (252 mm2) of the proposed LC-based antenna is 40% of the area of the prior LC-based antenna (625 mm2).

A low‐profile wideband planar phased array of cavity‐backed slot microstrip elements for two‐dimensional beam scanning applications

AbstractA low‐profile wideband planar phased array, working in X band and with two‐dimensional (2‐D) beam scanning characteristic is presented. In order to meet the requirements of wideband 2‐D beam scanning and low‐profile performance, a cavity‐backed slot stacked microstrip element is introduced. The array element is mainly composed of the open‐ended microstrip line printed on the bottom substrate, which backed by a rectangular metal cavity, and dual layer patches etched on the middle substrate and the top substrate, respectively. A vertical transition structure is used to feed the microstrip line and connect the active T/R module, which is similar to the coaxial probe. The thickness of the proposed element is only 4.5 mm (0.12 λL, λL is the wavelength of the lowest frequency). Based on the simulated design, an 8 × 8 planar phased array prototype has been fabricated and measured. The experimental results show that the proposed array have achieved the maximum scanning angle of ±45° in the H‐plane and ± 30° in the E‐plane across the frequency range of 8 ~ 12 GHz. Therefore, the proposed array can be used as a sub‐array of larger low‐profile wideband phased arrays for 2‐D beam scanning applications, and also validate the introduced design concept.

Patterned surface alignment to create complex three-dimensional nematic and chiral nematic liquid crystal structures

ABSTRACT Combining liquid crystals (LCs) with well-designed anchoring patterns at the substrates offers tremendous potential for the development of functional electro-optic devices or stimuli-responsive actuators. Photo-alignment techniques nowadays allow an almost arbitrary control over the surface anchoring and this flexibility is used to design highly efficient flat optical LC components with different functionalities. Part of this research, dealing with nematic and chiral nematic LC between substrates with patterned azimuthal anchoring, is reviewed here. The focus is on understanding the self-assembly of complex structures, steered by an interplay between surface anchoring and LC elasticity. Additional insight into the LC bulk behaviour is obtained by comparing experimental results with numerical simulations of the director configuration. Periodic anchoring patterns with azimuthal rotation at the top and bottom substrate are studied, as well as ring-shaped alignment patterns with a 180° or 360° azimuthal rotation in a confined region in space. Different combinations of anchoring patterns at the top and bottom substrates are investigated and in addition to nematic liquid crystal (NLC), also short and long-pitch chiral nematic liquid crystal (CLC) is considered.

Surface Stabilized Topological Solitons in Nematic Liquid Crystals

Photo-alignment is a versatile tool to pattern the alignment at the confining substrates in a liquid crystal (LC) cell. Arbitrary alignment patterns can be created by using projection with a spatial light modulator (SLM) for the illumination. We demonstrate that a careful design of the alignment patterns allows the stabilization of topological solitons in nematic liquid crystal (NLC) cells, without the need for chirality or strong confinement. The created LC configurations are stabilized by the anchoring conditions imposed at the substrates. The photo-aligned background at both substrates is uniformly planar aligned, and ring-shaped regions with a 180° azimuthal rotation are patterned with an opposite sense of rotation at the top and bottom substrate. A disclination-free structure containing a closed ring of vertically oriented directors is formed when the patterned rings at the top and bottom substrate overlap. Thanks to the topological stability, a vertical director orientation in the bulk is observed even when the centra of both patterned rings are shifted over relatively large distances. The combination of numerical simulations with experimental measurements allows identification of the 3D director configuration in the bulk. A finite element (FE) Q-tensor simulation model is applied to find the equilibrium director configuration and optical simulations are used to confirm the correspondence with experimental microscopy measurements. The created LC configurations offer opportunities in the field of optical devices, light guiding and switching, particle trapping and studies of topological LC structures.

Design and analysis of 6CB nematic liquid crystal–based rectangular patch antenna for S-band and C-band applications

Abstract This article presents the design and analysis of 4-hexyl-4′-biphenylcarbonitrile (6CB) nematic liquid crystal (NLC)–based rectangular patch antenna for S-band and C-band communication applications. Two glass substrates with permittivity of 6.4, loss tangent of 0.01 and thickness of 1 mm each with 21 × 25 mm2 and 19 × 19 mm2 dimension has been used, and 0.005 mm air gap has been placed to fill 6CB NLC. A rectangular patch of 10 × 11 mm2 size has been considered over the top substrate to achieve the application specific bands. The designed antenna model-1 with air gap is resonating at 5 GHz (4.01–7.85 GHz) with minimum S 11 of −24.2 dB. The proposed antenna model-2 is filled with 6CB NLC in the air gap between glass substrates is resonating at 3.3 GHz (2.61–4.45 GHz) with minimum S 11 of −29.75 dB. Antennas of both air gaps filled, and liquid crystal material filled models are fabricated and tested through combinational analyser for validation. The correlation between transmitted and received signals of the antenna models are analysed with time domain analysis by taking the identical antennas in face to face and side by side condition. The simulated results from HFSS electromagnetic tool and fabricated antennas results in chamber are exhibiting good agreement with each other.

Simpanan Karbon Padang Lamun di Kawasan Pantai Nusa Lembongan, Klungkung, Bali

The seagrass ecosystem has great potential in absorbing of CO2 concentration in atmosphere, results of the process photosynthesis will be stored in form of biomass during seagrass still alive. The research purpose was to know carbon storage from the seagrass ecosystem at the top substrate (leaves) and bottom substrates (rhizome and roots) in Nusa Lembongan coastal area, Bali. The research location is divided into three stations with 27 points. Carbon stock was analyzed by using invasion method consisting of calculating the value of ash content, organic matter content and carbon content. The results found three seagrass species in the Nusa Lembongan coastal area: Thalassia hemprichii, Cymodocea rotundata and Enhalus acoroides. The most dominant spesies is the Thalassia hemprichii. The carbon stored at the top substrate (leaf) is 21.08 gC/m2 and the bottom substrates (rhizome and root) are 52.67 gC/m2. The total estimated carbon deposits in the Nusa Lembongan coastal area is 65.98 tonnes with carbon deposits in the bottom substrate are larger than the top substrate, which is 71% or 47.12 tons on the bottom substrate while 29% or 18.86 tons on the top substrate.

Microfluidic Separation of Blood Cells Based on the Negative Dielectrophoresis Operated by Three Dimensional Microband Electrodes

A microfluidic device is presented for the continuous separation of red blood cells (RBCs) and white blood cells (WBCs) in a label-free manner based on negative dielectrophoresis (n-DEP). An alteration of the electric field, generated by pairs of slanted electrodes (separators) that is fabricated by covering parts of single slanted electrodes with an insulating layer is used to separate cells by their sizes. The repulsive force of n-DEP formed by slanted electrodes prepared on both the top and bottom substrates led to the deflection of the cell flow in lateral directions. The presence of gaps covered with an insulating layer for the electric field on the electrodes allows the passing of RBCs through gaps, while relatively large WBCs (cultured cultured human acute monocytic leukemia cell line (THP-1 cells)) flowed along the slanted separator without passing through the gaps and arrived at an edge in the channel. The passage efficiency for RBCs through the gaps and the arrival efficiency for THP-1 cells to the upper edge in the channel were estimated and found to be 91% and 93%, respectively.

Where is the best site for loading nanoparticles in a membrane? To achieve a high flux and cephalexin separation simultaneously

In this research, with the aim of achieving a high flux and rejection of cephalexin antibiotic simultaneously, separate modifications were performed on the membrane top layer (selective layer) and substrate layer (support layer). Fe3O4 (Fe) and ZrO2 (Zr) nanoparticles were synthesized for modifying the PAN support layer, while Fe3O4/ZrO2 (FZ) nanoparticles were synthesized for modifying the PA top layer. In this regard, five types of nanocomposite membranes were synthesized: In order to regulate the porosity of the support layer, PAFe2@PAN and PAZr2@PAN membranes were synthesized which showed more pores number compared to PAPAN membrane. In order to enhance the surface hydrophilicity, FZ2@PAPAN membrane was synthesized, which showed around 16% lower contact angle and 58% greater roughness compared to PAPAN membrane. In order to compensate for the roughness developed on the membrane surface, concurrent modifications were performed on the top and support layers; the FZ2@PAFe2@PAN and FZ2@PAZr2@PAN membranes were synthesized, which separated cephalexin by 91% and 95.8%. Comparison of the performance of the synthesized membrane with that of commercial FILMTEC (NF270-2450) membrane showed that the cephalexin rejection (95 ± 1) and flux recovery (99 ± 1) of FZ2@PAZr2@PAN are almost the same as cephalexin rejection (98 ± 1) and flux recovery (96 ± 1) of commercial membrane. From permeation point of view, FZ2@PAZr2@PAN membrane at transmembrane pressure of 4 bar and cross flow velocity of 0.5 m/s had a water flux of 49 L/m2.h and cephalexin flux of 38 L/m2.h, while NF270-2450 at the same condition had a water flux of 42 L/m2.h and cephalexin flux of 25 L/m2.h.

넓은 앙각 커버리지를 위한 3×4 재구성 급전회로를 갖는 5 GHz 무인항공기용 배열 안테나 설계

This paper presents a 5 GHz UAV array antenna with a 3×4 reconfigurable feeding network for wide elevation coverage. The proposed array comprises a four-element printed dipole antenna array in the top substrate, two supports with a tapered balun, a self-reflector for gain improvement, and a reconfigurable feeding network in the bottom substrate. For wide beam coverage, the feeding network comprises one RF switch, one Wilkinson power divider, and two 90° hybrid couplers; further, the network achieves wide beam coverage using one broadside beam and two end-fire beams. The measured impedance bandwidth, peak gain, and half-power beamwidth of the proposed array operated from 5.03 to 5.15 GHz are approximately 850 MHz(17 %), 6.7 dBi, and 180°, respectively.

Ordering of Oblate Hard Particles between Hybrid Penetrable Walls.

We report a Monte Carlo (MC) simulation study of a model discotic liquid crystal (DLC) confined between hybrid walls with controllable penetrability. The model consists of oblate hard Gaussian overlap (HGO) particles. Particle–substrate interactions are modeled as follows: each substrate sees a particle as a disc of zero thickness and diameter D less than or equal to that of the actual particle, σ0, embedded inside the particle and located halfway along, and perpendicular to, its minor axis. This allows us to control the anchoring properties of the substrates, from planar (edge-on) for D ≈ 0 to homeotropic (face-on) for D ≈ σ0, which can be done independently at either substrate. Depending on the values of Ds ≡ D/σ0 at the top (Dst) and bottom (Dsb) substrates, we find domains in (Dsb, Dst) space in which particle alignment is uniform planar (UP), is uniform homeotropic (UH), or varies linearly from planar at one substrate to homeotropic at the other (Lin). These domains are separated by regions of bistability (P–Lin and H–Lin), which appear to be wider than for prolate HGOs, and there may be also a small tristable (P–H–Lin) region. Results are compared with the predictions of density functional theory, implemented at the level of Onsager’s second-virial approximation with Parsons-Lee rescaling. As in the case of symmetric confinement studied previously, the agreement between theory and simulation is substantially less good than for prolate HGOs: in particular, for the investigated substrate separation L = 6σ0, the Lin configuration is never predicted. These discrepancies are likely a consequence of the fact that Onsager’s theory is less accurate for discs than for rods.

Hysteresis in the underdamped three-layer model

The hysteretic phenomena were investigated in the three-layer model consisting of a chain of harmonically interacting atoms confined between two rigid periodical substrate potentials, where the top substrate was driven by a external force. The pinning to running and the running-to pinning transitions were examined as the driving force was varied and the influence of the equilibrium spacing and strength of the interaction of the particles in the middle layer on the static and kinetic friction force analyzed in detail. The parameter space in which the friction forces could reach their maxima or minima was determined. These results could be interesting for the selection of lubricant materials and minimization of energy loss in tribology.

An on-demand bench-top fabrication process for fluidic chips based on cross-diffusion through photopolymerization.

In this paper, we propose a novel approach to fabricate fluidic chips. The method utilizes molecular cross-diffusion, induced by photopolymerization under ultraviolet (UV) irradiation in a channel pattern, to form the channel structures. During channel structure formation, the photopolymer layer still contains many uncured molecules. Subsequently, a top substrate is attached to the channel structure under adequate pressure, and the entire chip is homogenously irradiated by UV light. Immediately thereafter, a sufficiently sealed fluidic chip is formed. Using this fabrication process, the channel pattern of a chip can be designed quickly by a computer as binary images, and practical chips can be produced on demand at a benchtop, instead of awaiting production in specialized factories.

Cell Behavior within Nanogrooved Sandwich Culture Systems.

Grooved topography and inherent cell contact guidance has shown promising results regarding cell proliferation, morphology, and lineage-specific differentiation. Yet these approaches are limited to 2D applications. Sandwich-culture conditions are developed to bridge the gap between 2D and 3D culture, enabling both ventral and dorsal cell surface stimulation. The effect of grooved surface topography is accessed on cell orientation and elongation in a highly controlled manner, with simultaneous and independent stimuli on two cell sides. Nanogrooved and non-nanogrooved substrates are assembled into quasi-3D systems with variable relative orientations. A plethora of sandwich-culture conditions are created by seeding cells on lower, upper, or both substrates. Software image analysis demonstrates that F-actin of cells acquires the orientation of the substrate on which cells are initially seeded, independently from the orientation of the second top substrate. Contrasting cell morphologies are observed, with a higher elongation for nanogrooved 2D substrates than nanogrooved sandwich-culture conditions. Correlated with an increased pFAK activity and vinculin staining for sandwich-culture conditions, these results point to an enhanced cell surface stimulation versus control conditions. The pivotal role of initial cell-biomaterial contact on cellular alignment is highlighted, providing important insights for tissue engineering strategies aiming to guide cellular response through mechanotransduction approaches.

Characteristics and Thermal Shock Resistance of HVOF-Sprayed TiAlNb Coatings

Two Ti-63.39Al-8.26Nb-0.2Y powders (powder 1 and powder 2) were fabricated by rapid in situ reaction and arc melting, respectively, then deposited on 316L stainless-steel substrate by the high-velocity oxygen fuel (HVOF) process. The phase composition, microstructure, porosity, microhardness, and adhesive strength of the two kinds of coating (DC1 and DC2) were characterized. DC1 had lower porosity, higher microhardness, and higher adhesive strength than DC2, which can be attributed to the difference in particle size distribution and mean particle size; a narrow particle size distribution and suitable mean particle size favor the formation of a HVOF coating with denser and more uniform microstructure. The thermal shock behavior was investigated by heating and water quenching from 600 °C to room temperature. The results showed that the failure of both TiAlNb coatings occurred due to spallation of the top coat, but the thermal shock resistance of DC2 was better than that of DC1. Thermal stress concentration caused by thermal expansion mismatch between the top coat and substrate was recognized as the major reason for TiAlNb coating failure.