Small Pitch Research Articles

Fast response electrically controlled liquid crystal lens array for high resolution 2D/3D switchable display.

A fast response electrically controlled liquid crystal (LC) lens array is revealed. In order to realize the fast response, a double LC layer structure is adopted. The fabricated LC lens array has a small pitch of 310µm and LC layer with a thickness of 50μm. Experimental results show that the focal length of the LC lens array can be continuously adjusted by low driving voltage (∼6.5Vrms), and the shortest focal length is 0.5mm. The switching between 2D display and 3D display is realized by controlling the voltage off and on state of the LC lens array. Experimental result shows that the 2D/3D switchable display has a fast response time of 16ms. The short pitch LC lens array is expected to be used in high-resolution 2D/3D switchable display.

Performance of passivation layer for InP/InGaAs based short-wave infrared photodetector

The surface passivation effects of SiNx films deposited by plasma-enhanced chemical vapour deposition (PECVD) technique are investigated for InP/In0.53Ga0.47As mesa type photodetectors. It is found that the deposited SiNx film effectively reduces the densities of interface states (Dit) and slow trapped charge (Nt) near SiNx/In0.53Ga0.47As interface using NH4OH based pre-passivation treatment. The fixed charge density of 1.98 × 1011 C/cm2, the minimum value of Dit ∼3.2 × 1011 cm−2 eV−1 and Nt of 4.2 × 1011 C/cm2 are determined from the experimental capacitance-voltage curve of Ti–Au/SiNx/In0.53Ga0.47As based metal-insulator-semiconductor structure. Lower values of passivation properties indicate smaller surface recombination centre and lower surface leakage current. Thus, minimum noise related to dark current could be achieved for InP/In0.53Ga0.47As based mesa structured detector array with smaller pitch at room temperature.

Design of vibro-impact electromagnetic ocean-wave energy harvesting system; an experimental study

Ocean wave energy is a stable renewable energy source, which has realistic application prospects. Based on the intermittent and irregular nature of ocean-wave, researchers have designed many ocean-wave energy harvesters, with several advantages and disadvantages. The main goal of this study is to present a new ocean wave energy harvester, which works based on the small pitch motion of moving floaters. Unlike almost all the previously presented systems, the presented ocean wave energy harvester can work in moving forward ships and boats like emergency boats. To do so, a ibro-impact system is designed to gather the kinetic energy of small pitch motions and transmit it to the vibratory part of the system via impulsive load. A mechanical rectifier that gets its input energy from the oscillations of the vibratory part, provides continuous rotations needed by the electromagnetic transducer. The governing electromechanical equation of motion for the discussed system is derived to study the effects of changing the ocean-wave properties on the application of the energy harvester. It is shown the gap size of the impact part of the system and the ocean-wave period have important effects on the output electrical energy.

Novel Backside Structure for Reverse Conducting Insulated-Gate Bipolar Transistor With Two Different Collector Trench

A novel reverse-conducting insulated gate bipolar transistor (RC-IGBT) with two different collector trench (DCT) is proposed. One of the collector trenches is filled with heavily doped N-type polysilicon (N-poly) and the other is filled with heavily doped N- and P-poly. An electron accumulation layer is formed along the sidewall of trench owing to built-in potential difference between the N-poly and the N-drift region. The electron accumulation layer and collector trenches block the electric field, which behaves just like the N-buffer layer of the conventional RC-IGBT (Con. RC-IGBT). Similarly, due to potential difference between the P-poly and N-drift region, a high-density hole inversion layer is formed to narrow the electron current path as a high resistance. The DCT RC-IGBT achieves snapback-free in a small cell pitch without additional control. Moreover, the DCT RC-IGBT shows better tradeoff between turn-off loss and ON-state voltage drop than that of con. RC-IGBT. For the same forward voltage drop, the turn-off loss is reduced by 26%.

A two-dimensional thermodynamic model based on Helmholtz free energy for wettability regulation of textured metal surfaces

To provide theoretical support for the wettability regulation of textured metal surfaces, a two-dimensional (2-D) thermodynamic model based on Helmholtz free energy is proposed to reveal the nature of the infiltration phenomenon. The relationship between the apparent contact angle and the free energy of the infiltration system is established. Micropyramid arrays (MPAs) with different pitches are textured on a high-phosphorus electroless nickel-phosphorus (Ni-P) alloy plating by ultraprecision machining for the verification of the theoretical model. The results show that the minimum free energy corresponds to the apparent contact angle of the water droplet when it is stable on the textured surface. MPA-textured surfaces with smaller pitches have a wider variation range of apparent contact angle and are expected to achieve better hydrophobicity. Periodic energy barriers created by the MPAs promote the free energy consumption. By employing ultrasonic assistance, secondary microstructures are generated on the inclined sidewalls of the micropyramids, thus enhancing the energy barrier effect. A maximum apparent contact angle of 124.4° is obtained for the MPA-textured surface machined with ultrasonic vibration when the pitch is 20 μm. The experimental apparent contact angle values are all within the theoretical range, indicating the feasibility of the theoretical model.

Numerical validation of simple non-stationary models for self-propelled pitching foils

High-resolution numerical simulations of the self propelled locomotion of two-dimensional pitching foils are used to assess simplified models based on linear potential theory for the fluid-foil interaction. These models are very useful because they provide simple analytical estimations of the swimming velocity, among other relevant features of the aquatic locomotion of fishes and underwater robotic devices propelled by flapping foils. In particular, we consider a pitching foil self-propelled from two different models of the unsteady thrust force based on linear potential theory, both complemented with a new simple model for the unsteady viscous friction obtained from the present full-numerical simulations, valid in a wide range of Reynolds numbers (103≲Re≲104) of interest for many natural and robotic swimmers. The resulting ordinary differential equation for the swimming velocity is easily integrated numerically, comparing favorably with the full-numerical simulations for small pitch amplitudes (Strouhal numbers St≲0.25) and the above range of Reynolds numbers. Further, when the swimming velocity is small, simple approximate solutions of the dynamic model equation are obtained, whose pitch amplitude validity range is more limited than the numerical solution of the model as the Reynolds number and the foil mass ratio increase, becoming negligibly small when the frequency-based Reynolds number is well over 104. Although both thrust models yield similar quantitative results, they predict qualitatively different dependencies of the swimming velocity on the different non-dimensional parameters.

Visual occlusion effects on youth football players' performance during small-sided games.

This study aimed to explore how youth players’ physical, technical and positional performance may be affected by visual occlusion when playing under different SSG pitch sizes. Under-15 players performed two experimental scenarios: a) normal situation, without visual occlusion; b) visual occlusion, by using an eye patch in the eye corresponding to the dominant foot. These scenarios were tested in a small (40x30m) and a larger pitch (50x35m). Players’ positional data was used to compute tactical and time-motion variables. In addition, technical analysis was comprised using video footage. Playing with visual occlusion in the larger pitch size induced higher distance covered while walking but lower running distance (p < .05). Although no statistically significant effects were identified between the normal and visual occlusion conditions for the tactical behaviour and technical performance a lower number of successful passes (small to moderate effect sizes) and higher regularity in the distance to the opponent’s team centroid (moderate effect size) were found with visual occlusion. Players covered more distance and achieved higher maximum speed in the larger compared to the small pitch (moderate to large effect size, p < .05), while also increasing their distance to both team’s centroid and increasing the regularity to these distances (moderate to large effect size, p < .05). Overall, despite similar effects for tactical and technical variables, some important practical information can be depicted. Accordingly, coaches may use the visual occlusion to promote more stable and regular behaviors while decreasing the physical demands. Larger pitches may be used to increase the distance between players’ and teams, as well as to induce higher physical load in both the normal and visual occlusion conditions. From the technical perspective, coaches may design smaller pitches to emphasize the use of the non-dominant foot during the occlusion scenario and promote the pass during the normal scenario.

Airside thermal-hydraulic and fouling performances of economizers with integrally-molded spiral finned tubes for residual heat recovery

Without defects inherent in conventional welded finned tubes, nonwelded integrally-molded spiral finned (IMSF) tubes proposed here have “zero” contact thermal resistance and high joint strength out of trapezoidal cross-section of the fin, and thus greatly improve thermal performances and service life of economizers for residual heat recovery. To guide the applications of this new economizer, a three-dimensional physical-numerical model is established to study airside thermal-hydraulic and fouling performances of the economizer with IMSF-tubes. We investigate the effects of longitudinal and transverse pitches of finned tube bundles on the airside thermal-hydraulic and fouling performances of IMSF-tubes at various Reynolds numbers. The results show that a longitudinal pitch more than 80 mm is suggested for economizer design to avoid working instability of boiler systems due to high pressure drop at small longitudinal pitch, and as compromised, a transverse pitch of an economizer may be more than 100 mm since a small transverse pitch improves thermal-hydraulic performance, but worsens fouling and raises pressure drop. We also put forward new correlations of the Colburn and Fanning friction factors for the IMSF-tube economizer. Compared with other finned tubes, IMSF-tubes improve not only mechanics but also thermal-hydraulic performances of heat exchangers. Our research work may contribute to applications of IMSF-tube economizers for residual heat recovery.

Novel High-Tolerance Termination With Resistive Field Plate for 600 V Super-Junction Vertical Double-Diffused MOSFET

In this letter, a novel high-tolerance termination is proposed for 600 V super-junction vertical double-diffused MOSFET (SJ VDMOS). By using a multi-ring resistive field plate between the active region and edge ring, the narrow charge tolerance of termination for small cell pitch SJ VDMOS is improved remarkably. The surface field plate can dynamically deplete the excess charges and introduce additional electric field peaks, effectively counteracting the degradation caused by charge imbalance. Combined with the symmetrical folded layout, the tolerance of the P-type lateral connection (LC) layer reaches &#x00B1;21.7&#x0025;, and the design window of the P-pillar extends to the same range as that of the active region. This provides great flexibility for the design of the LC layer and even JFET and P-pillar implantation.

Probing Dark Current Random Telegraph Signal in a Small Pitch Vertically Pinned Photodiode CMOS Image Sensor After Proton Irradiation

The dark current degradation and dark current random telegraph signal (DC-RTS) after proton irradiation are studied in new scale silicon microvolumes by using a commercial CMOS image sensor. Results show that previously reported empirical models describing the displacement damage-induced degradations are still valid despite the 10–100 times smaller depletion volume used. In addition, no evidence of significant total ionizing dose effects is observed. Finally, the reduction of the fraction of RTS pixels detected and the fraction of multilevel RTS pixels is directly linked to the reduction in pixel volume.

Generalized focal plane array modulation transfer function estimation approach for nonstationary laser speckle random processes

The infrared (IR) imaging community has a need for direct IR detector evaluation due to the continued demand for small pixel pitch detectors, the emergence of strained-layer-superlattice devices, and the associated lateral carrier diffusion issues. Conventional laser speckle-based modulation transfer function estimation is dependent on Fresnel propagation and limited to paraxial geometries, preventing the utilization of this approach on small pixel pitch IR devices. This paper presents a generalized approach for determining a focal plane array (FPA) system input power spectral density, utilizing numerical evaluation of Rayleigh–Sommerfeld speckle irradiance autocorrelation functions, speckle irradiance spectral analysis using the Wigner distribution function, and experimental error quantification incurred from making wide-sense-stationary assumptions regarding the associated laser speckle random process. The effort’s final result is an experimental demonstration of an FPA resolution estimation technique valid in nonparaxial test scenarios.

P‐24: Distinguished Student Poster: Gate Driver with LTPO‐TFT Circuits for Low Power Consumption and Narrow Bezel AMOLED Displays

We propose a novel gate driver circuit using low‐temperature polycrystalline silicon and oxide (LTPO) thin‐film transistors (TFTs). The proposed circuit operates well when oxide TFTs have VTH of −7.5 V, which is very depletion mode. In addition, by utilizing extremely low off‐state current of oxide TFTs, ultra‐low power consumption can be achieved. The proposed circuit consists of only six TFTs, four p‐type LTPS and two n‐type a‐IGZO TFTs, without capacitor. The fabricated circuit operates with a pulse width of 1 μs corresponding to operating speed of 500 kHz with very small pitch. The proposed circuit can be applied to ultra‐high definition (UHD) and narrow bezel AMOLED display.

Mathematical modelling and theoretical research of micropositioning system

In this paper, modelling and theoretical research of micropositioning system with stepper motor are proposed. The aim of our research is to provide a method, which is suitable for modelling a ball-screw based positioning system controlled by a stepper motor. A created dynamical model of micropositioning system mechanical parts. The second type of Lagrange equation is used to construct the mathematical model. For modelling micropositioning systems, Matlab/SIMULINK software is used. MatLab is used to perform calculations of some equations, and SIMULINK is used to create a dynamic model of a micropositioning system and simulate system operation. Analysis of motion smoothness showed that even for systems with relatively small screw radius and pitch 1/4 microstepping mode are unable to provide smooth movement. The smoother the movement, the less energy is required to overcome friction.

On the Short Circuit Electro-Thermal Failure of 1.2 kV 4H-SiC MOSFETs with 3D Cell Layouts

In this manuscript, the short circuit (SC) capability of 1.2 kV vertical double diffused SiC MOSFET with different layout topologies is investigated. 3D finite element electro-thermal simulations have been carried out in order to assess the performance of five different cell topologies. It has been found that while the maximum drain current density observed during a SC event agrees well with the specific on-state resistance behaviour, the maximum temperature evolution in the unit cell follows the opposite trend. This behaviour can be explained by the relatively poor spreading of the carriers in the JFET region (of the ALL) at small cell pitches (~ 8um), which can lead to the formation of a filament with a high current density and heat generation.

Numerical investigation on flow and thermal performance of supercritical CO2 in a horizontal ribbed tube

The numerical simulation is performed to investigate the thermal performance of supercritical carbon dioxide (sCO2) in horizontal ribbed tubes at mass flux ranging from 200 kg/(m2·s) to 400 kg/(m2·s), heat flux, 20 kW/m2 to 30 kW/m2, pressure 8–9 MPa and inlet temperature 290–310 K. Three types of ribs were selected to investigate the effects of rib geometry, buoyancy and rib parameters on the thermal-hydraulic performance. The results indicated that the triangular ribbed tube (TRT) could significantly improve the heat transfer coefficient (HTC) and reduce the wall temperature. Nevertheless, circular ribbed tubes have the best performance from the performance evaluation criteria (PEC) viewpoint. Moreover, the rib configuration promotes the transition of the flow field from “flattened shape” to “U-shaped”, which improves the heat transfer. Finally, small rib size and medium pitch can further enhance supercritical CO2 turbulent heat transfer.

Influence of Cross-Section and Pitch on the Mechanical Response of NiTi Endodontic Files under Bending and Torsional Conditions-A Finite Element Analysis.

In this article, the effects of cross-section and pitch on the mechanical response of NiTi endodontic files is studied by means of finite element analyses. The study was conducted over a set of eight endodontic rotary files, whose geometry was obtained from combinations of two cross-sections (square and triangular) and four pitches. Each file was subjected to bending and torsional analyses, simulating the testing conditions indicated in the ISO 3630 Standard, in order to assess their stiffness and mechanical strength. The results indicate that endodontic files with a square cross-section have double the stiffness of those with triangular cross-sections, both in terms of bending and torsion. For both loading modes, endodontic files with a triangular cross-section can undergo larger deformations before overload failure than those with a square cross-section: up to more in bending and in torsion. Moreover, under equivalent boundary conditions, endodontic files with triangular cross-sections present a higher fatigue life than those with square cross-sections: up to more than higher for small pitches. The effect of pitch on the stiffness and strength of the file is smaller than that of the cross-section shape, but smaller pitches could be beneficial when using a triangular cross-section, as they increase the bending flexibility, fatigue life, and torsion stiffness. These results suggest a clinical recommendation for the use of files with a triangular-shaped cross-section and a small pitch in order to minimize ledging and maximize fatigue life. Finally, in this study, we reveal the sensitivity of the orientation of files with respect to the bending direction, which must be taken into account when designing, reporting, and interpreting test results under such loading conditions.

Plasma-based area selective deposition for extreme ultraviolet resist defectivity reduction and process window improvement

Extreme ultraviolet (EUV) lithography has overcome significant challenges to become an essential enabler to the logic scaling roadmap. However, it remains limited by stochastically driven defects, such as line breaks and line bridges for aggressive pitches. This is especially relevant for the back end of line, which requires the most aggressive scaling. Stochastic defects reduce device yield and may push device manufacturers to move to EUV multipatterning beyond 36 nm pitch single exposure, which is a costly option. While the lithography and patterning stack can be optimized to provide the largest process window with the lowest number of defects, process margins decrease as smaller pitches are required. Currently, for some lithography stacks, especially spin-on glass based trilayer stacks, the defect-free process window beyond 36 nm pitch is limited by line collapse. Reduction in resist thickness may mitigate pattern collapse, but it may also increase the number of line breaks—trading one killer defect for another. In this paper, we expand on an area selective deposition (ASD) process in situ of an etch chamber to selectively deposit material on the EUV photoresist prior to transferring the pattern downstream. We demonstrate mitigation of resist line notching and breaks while maintaining deposition-free open areas and clear alignment marks. Due to the inherent chemical selectivity of the deposition process as opposed to a purely aspect ratio driven deposition process, thinner resists that, with a normal etch condition would result in line breaks, can now be considered. This drives down flopover defect issues seen with thicker EUV resists and enables several underlayer systems that could otherwise not be considered. Finally, we demonstrate that defectivity levels measured by e-beam inspection post lithography and post pattern transfer and yield are both improved at 30 nm pitch when this ASD process is used.

Using The Helix Mixing Approach On Floating Offshore Wind Turbines

In recent years dynamic induction control has shown great potential in reducing wake-to-turbine interaction by increasing the mixing in the wake. With these wake mixing methods the thrust force will vary in time. If applied to a floating offshore wind turbine, it will cause the platform to move. In this paper the effect of the Helix mixing approach on a DTU10MW turbine on the TripleSpar platform and its wake is evaluated. When the Helix mixing approach is applied at Strouhal equal to 0.25, the yaw movement is excited close to the eigenfrequency of the platform resulting in significant yaw angles for small blade pitch angles. To understand the impact of the motion on the wake, the yaw motion is simulated using the free wake vortex method as implemented in Qblade. Under laminar inflow, results show that the windspeed at a distance of 5 rotor diameters downstream can be increased by up to 10% compared to a fixed-bottom turbine.

Simulations of optical reflectance in vertically aligned GaAs nanowires array: The effect of the geometrical structural parameters

We report the effects of radius-, length- and pitch-sizes on the optical reflectance of a periodic square array of GaAs nanowires embedded in epoxy. The simulated system is a multilayer array constituted by alternating layers of epoxy and an effective medium of GaAs nanowires embedded in epoxy. For both s- and p-polarizations, we observe an oscillating behavior in the reflectance spectra, as a consequence of interferences in periodical systems. We found that the radius- and pitch-sizes significantly affect the reflectance of GaAs nanowires array, while the length-sizes do not present evidence of changes in the optical reflectance. For higher radius, the number of oscillations increases and consequently, the peak-to-peak distance decreases. Besides, there is a red-shift of the reflectance for increasing radius. For higher pitch, the number of oscillations also increases, and a red-shift is observed. We obtain dependence laws for the peak-to-peak distance and red-shift versus radius and versus pitch. These dependences obey approximate quadratic relations. Attending to the reflectance dependence on the light incidence angle, we have found that for s-polarized light, the reflectance is higher with increasing angles, in comparison to p-polarized light cases, independently of the radius and pitch values. For both polarizations, we found that the reflectance is increasing for greater radii and smaller pitches, independently of the incident angle.

Colloidal III-V Quantum Dot Photodiodes for Short-Wave Infrared Photodetection.

Short‐wave infrared (SWIR) image sensors based on colloidal quantum dots (QDs) are characterized by low cost, small pixel pitch, and spectral tunability. Adoption of QD‐SWIR imagers is, however, hampered by a reliance on restricted elements such as Pb and Hg. Here, QD photodiodes, the central element of a QD image sensor, made from non‐restricted In(As,P) QDs that operate at wavelengths up to 1400 nm are demonstrated. Three different In(As,P) QD batches that are made using a scalable, one‐size‐one‐batch reaction and feature a band‐edge absorption at 1140, 1270, and 1400 nm are implemented. These QDs are post‐processed to obtain In(As,P) nanocolloids stabilized by short‐chain ligands, from which semiconducting films of n‐In(As,P) are formed through spincoating. For all three sizes, sandwiching such films between p‐NiO as the hole transport layer and Nb:TiO2 as the electron transport layer yields In(As,P) QD photodiodes that exhibit best internal quantum efficiencies at the QD band gap of 46±5% and are sensitive for SWIR light up to 1400 nm.