Gap Spacer Research Articles

Ultrabroadband Photodetection with MoS2 and Gold Nanorod Using Gap-Mode Plasmon Effect.

Plasmon resonance using metal nanostructures enables the realization of high-performance optoelectronic devices via field enhancements in the vicinity of the metal nanostructure. This study proposes an ultrabroadband MoS2 photodetector based on the gap-mode plasmon of gold nanorods. The use of MoS2 as a gap spacer for the gap-mode plasmon effect and as a channel material for the photodetector is demonstrated. The proposed photodetector demonstrates superior performance, a high photoresponsivity of 2.8 A/W at a near-infrared wavelength of 1100 nm, and a fast response time of 17 μs. In addition to the gap-mode plasmon effect of the gold nanorod enhancing the photoresponsivity from 1.13 to 8.7 A/W, the lateral surface plasmon resonance of the gold nanorods enhances the absorption of the longitudinal mode of the gold nanorods (near-infrared to infrared range). Further, the gap-mode plasmon effect of the gold nanorods enhances the absorption of the transverse mode of the gold nanorods (visible range), thus realizing ultrabroadband photodetection. Therefore, the proposed device design strategy contributes significantly to overcoming the trade-off between photoresponsivity and response time.

Metal to insulator transition for conducting polymers in plasmonic nanogaps

Conjugated polymers are promising material candidates for many future applications in flexible displays, organic circuits, and sensors. Their performance is strongly affected by their structural conformation including both electrical and optical anisotropy. Particularly for thin layers or close to crucial interfaces, there are few methods to track their organization and functional behaviors. Here we present a platform based on plasmonic nanogaps that can assess the chemical structure and orientation of conjugated polymers down to sub-10 nm thickness using light. We focus on a representative conjugated polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), of varying thickness (2-20 nm) while it undergoes redox in situ. This allows dynamic switching of the plasmonic gap spacer through a metal-insulator transition. Both dark-field (DF) and surface-enhanced Raman scattering (SERS) spectra track the optical anisotropy and orientation of polymer chains close to a metallic interface. Moreover, we demonstrate how this influences both optical and redox switching for nanothick PEDOT devices.

Microlens array camera with variable apertures for single-shot high dynamic range (HDR) imaging.

We report a microlens array camera with variable apertures (MACVA) for high dynamic range (HDR) imaging by using microlens arrays with various sizes of apertures. The MACVA comprises variable apertures, microlens arrays, gap spacers, and a CMOS image sensor. The microlenses with variable apertures capture low dynamic range (LDR) images with different f-stops under single-shot exposure. The reconstructed HDR images clearly exhibit expanded dynamic ranges surpassing LDR images as well as high resolution without motion artifacts, comparable to the maximum MTF50 value observed among the LDR images. This compact camera provides, what we believe to be, a new perspective for various machine vision or mobile devices applications.

Extending Plasmonic Enhancement Limit with Blocked Electron Tunneling by Monolayer Hexagonal Boron Nitride.

Fabricating ultrasmall nanogaps for significant electromagnetic enhancement is a long-standing goal of surface-enhanced Raman scattering (SERS) research. However, such electromagnetic enhancement is limited by quantum plasmonics as the gap size decreases below the quantum tunneling regime. Here, hexagonal boron nitride (h-BN) is sandwiched as a gap spacer in a nanoparticle-on-mirror (NPoM) structure, effectively blocking electron tunneling. Layer-dependent scattering spectra and theoretical modeling confirm that the electron tunneling effect is screened by monolayer h-BN in a nanocavity. The layer-dependent SERS enhancement factor of h-BN in the NPoM system monotonically increases as the number of layers decreases, which agrees with the prediction by the classical electromagnetic model but not the quantum-corrected model. The ultimate plasmonic enhancement limits are extended in the classical framework in a single-atom-layer gap. These results provide deep insights into the quantum mechanical effects in plasmonic systems, enabling the potential novel applications based on quantum plasmonic.

Quantification of the Real Plasmonic Field Transverse Distribution in a Nanocavity Using the Vibrational Stark Effect.

Quantifying the real plasmonic field strength experimentally has been long pursued in expanding the applications related to plasmonic enhancement. However, it is still an enormous challenge to determine the inhomogeneous plasmonic field distribution. Here, self-assembled monolayers (SAMs) of 4-mercaptobenzonitrile (MBN) are sandwiched as a gap spacer in a nanoparticle-on-mirror (NPoM) structure, effectively forming ultrahigh field enhancement to observe Stark shifts of the chemical bond. Transverse position-dependent Stark shifts of ν(C═C) and ν(C≡N) in the individual nanocavity measured by surface-enhanced Raman scattering (SERS) experiment combined with the Stark tuning rate by density functional theory (DFT) simulation accurately revealed the inhomogeneous plasmonic field transverse distribution and quantified the transverse plasmonic field strength up to ∼1.9 × 109 V/m, which matches the value predicted by finite element method (FEM) simulation. This work deepens the insight into plasmon-based technologies and will coordinate high-resolution techniques such as tip-enhanced Raman spectroscopy (TESR) to reveal the real plasmonic field distribution.

Acoustic metasurfaces for efficient matching of non-contact ultrasonic transducers

Air-coupled ultrasonic techniques based on rapid and contactless inspection are useful for various applications, such as ranging finding, surface profile measurement, and non-destructive evaluation. However, impedance matching issues between air and piezoelectric materials lead to technical limitations, such as imaging resolution and penetration depth. In order to mitigate these problems, we utilize acoustic metasurfaces consisting of periodic concentric ring arrays with narrow slits and tiny air gap spacers. Narrow slits induce Fabry–Pérot resonance with respect to slit thickness, and tiny gap spacers generate half-wave resonance with respect to the period. Here, we utilize the coupled resonance combined with slit resonance and gap resonance. These coupled resonances lead to efficient impedance matching of airborne sound from ultrasonic transducers. Thus, these metasurfaces lead to a broadband sound pressure level gain in the frequency range of 0–80 kHz. Enhanced pulse signals using the pulse-echo and through-transmission ultrasonic techniques are achieved.

Atomically thin Schottky junction with a gap-mode plasmon for enhanced photoresponsivity in MoS2-based photodetectors

Two-dimensional (2D) materials present various extraordinary properties that are advantageous in optoelectronic devices with atomically thin nature. Despite their excellent light–matter interaction, a low optical absorption that is proportional to thickness is considered to be a major limitation. In this study, a gap-mode plasmon structure is applied to the Schottky junction of Au–MoS2 to compensate for its low absorption. The magnitude of the gap-mode plasmon is generally known to be inversely proportional to the gap distance between two metal nanostructures; hence, an atomically thin 2D material can be considered to be a good candidate for a gap spacer. Owing to the gap-mode plasmon structure, the photoresponsivity of the proposed device is enhanced by approximately 11.6 times from 25 to 290 A W−1 under 1 nW of laser power, without photoresponse time degradation. Two operation modes, named the photovoltaic and the photoconductive mode, are also observed through different response times; these present different carrier transport mechanisms depending on the existence of bias voltage.

Design of Web-to-Web Spacing for the Reduced Pressure Drop and Effective Depth Filtration.

The study aims at lowering the pressure drop and extending the service life at a given set of filter materials implementing a space between the filter layers. As design factors, the web-to-web space was implemented by inserting either a bulk air gap or porous spacer web between the filter webs. The effect of spacing, either by the air gap or by the spacer web, on the pressure drop reduction was apparent for 4-layer constructions, and the effect was greater at the higher face velocity. The use of spacer web was more effective than the air gap in reducing the pressure drop, because the porous, fluffy spacer web acted as an effective air flow channel between the compact filter layers. The loading capacity was also increased with the spacer web implementation, effectively delaying the clogging point and extending the service life. Employing both experimental investigation and numerical simulation, this study intended to provide a practical design solution to the important problem in the field of air filtration. The results of this study can be used as a practical design guide to reduce pressure drop via depth filtration.

Pinch Off Plasma Chemical Vapor Deposition Process and Material Technology for Nano-Device Air Gap/Spacer Formation

EXTENDED ABSTRACT Continued integrated circuit scaling deeper into the nanoscale regime has provided improved performance through shrinking of the Front-End-of-Line (FEOL) device and Back-End-of-Line (BEOL) interconnect. With scaling, resistance-capacitance (RC) delay is an increasing challenge, limiting overall product performance. Capacitance reduction is therefore vitally important for device performance in both the FEOL and BEOL device structure. Conventional capacitance reduction methods for FEOL and BEOL while maintaining yield and reliability have required significant material innovations such lower-k cap and bulk dielectrics with required mechanical, structural, electrical and other properties. To improve capacitance, other innovations in device structure and process integration such as Air Gap and Air Spacer are also needed (1-2). The air spacer (FEOL) and air gap (BEOL) structures require novel process technology approaches such as pinch off deposition to optimize the capacitance reduction while maintaining yield and reliability. In this paper, we present an overview of material and process technology requirements for FEOL air spacer (1) and BEOL air gap (2) formation using a pinch off deposition approach. These approaches utilize established dielectric materials and processes such as Plasma CVD of SiN, SiCN, SiCOH, pSiCOH, in the formation of the air spacer/air gap. The selection of these dielectric materials and processes has a large impact in the void (gap) dimension and volume as typically show in figure 1. The void dimension and volume in airgap structures can be controlled with various dielectric deposition processes and materials as shown in Figure 1: (a) Long and wide voids for optimal capacitance reduction. (b) Short and wide voids for improved process fabrication and integration. (c) Short and narrow voids for better sidewall protection and device reliability but with a smaller capacitance reduction. The overall void dimension and type of dielectric material are strongly related to the total device capacitance reduction and reliability. Significant capacitance reduction with good reliability has been achieved through material, process and structural/architectural optimization with the pinch off deposition process approach on current 10 nm device structures as shown in figure 2 (FEOL Air spacer) and figure 3 (BEOL Air Gap). This work was performed by the Research Alliance Teams at various IBM Research and Development Facilities References 1) K. Cheng, S. Nguyen et al. International Electron Device Meeting, Proceeding Vol. 2016, paper 17.1, pp.444-447. San Francisco, USA 2) C. Penny, S. Gates, B. Peethala, J. Lee, D. Priyadarshini, S. Nguyen, P. McLaughlin, E. Liniger, C.-K. Hu, L. Clevenger, T. Hook, H. Shobha, P. Kerber, I. Seshadri, J. Chen, D. Edelstein, R. Quon, G. Bonilla, V. Paruchuri, and E. Huang, International Interconnect Technology Conference, Proceed. Volume, paper 2.2, May 16-18,2017, Taipei, Taiwan. Figure 1

Comprehensive condensation flow regimes in air gap membrane distillation: Visualization and energy efficiency

The thermal performance of air gap membrane distillation (AGMD) desalination is dominated by heat and mass transfer across the air gap between the membrane and the condensing surface. However, little is known about the impact of condensate flow patterns in some design variations of the air gap. In this study, air gap membrane distillation experiments were performed at various inlet temperatures, varying module inclination angle, condensing surface hydrophobicity, and gap spacer design to identify the effect of each on the permeate production rate and thermal efficiency of the system. Additionally, this study is one of the first with enhanced visualization of flow patterns within the air gap itself, by using a transparent, high thermal conductivity sapphire plate as the condenser surface. System-level numerical modeling is used to further understand the impact of these flow regimes on overall energy efficiency, including flux and GOR. A brief review of membrane distillation condensation regimes is provided as well. For tilting the AGMD flat-plate module, permeate flux was barely influenced except at extreme positive angles (> 80°), and moderate negative angles (< −30°), where condensate fell onto the membrane surface. The surface with the hydrophobic coating (for dropwise condensation) was shown to have better droplet shedding (with very small nearly spherical droplets) and fewer droplets bridging the gap. Superhydrophobic surfaces (for jumping droplet condensation) were similar, with much smaller droplet sizes. Such surfaces could improve AGMD efficiency while avoiding flooding, as better performance (2x higher GOR) is reached with much smaller gap sizes (<0.2 mm) than currently attainable gaps with filmwise condensation (>1 mm). Meanwhile, the hydrophilic surface for small gap sizes (< 3 mm) often had pinned regions of water around the hydrophilic surface and plastic spacer. Overall, the various results imply that the common assumption of a laminar condensate film poorly describes the flow patterns in real systems for all tilt angles and most spacer designs. Real system performance is likely to be between that of pure AGMD and permeate gap membrane distillation (PGMD) variants, and modeling shows that enhanced condensing in air gaps may improve system energy efficiency significantly, with strong relative advantages at high salinity.

Super-radiating manipulation of a nano-emitter by active toroidal metamaterials

The far-field radiation of a single dipolar emitter can be controlled by coupling to toroidal dipole resonance attached to metallic double flat rings, realizing a conversion from non- to super-radiating. The underlying physical mechanism is the hybridization interference of toroidal and electric dipoles under an asymmetric configuration by introducing a radial displacement of the dipolar emitter. By embedding gain medium in the gap spacer between double flat rings, the directional far-field super-radiating power can achieve a tremendous enhancement with a moderate requirement on the gain coefficient, promoting light-matter interaction manipulation.

First-principles spin-transfer torque in CuMnAs|GaP|CuMnAs junctions

We demonstrate that an all-antiferromagnetic tunnel junction with current perpendicular to the plane geometry can be used as an efficient spintronics device with potential high frequency operation. By using state-of-the-art density functional theory combined with quantum transport, we show that the N\'eel vector of the electrodes can be manipulated by spin-transfer torque. This is staggered over the two different magnetic sublattices and can generate dynamics and switching. At the same time the different magnetization states of the junction can be read by standard tunnelling magnetoresistance. Calculations are performed for CuMnAs$|$GaP$|$CuMnAs junctions with different surface terminations between the anti-ferromagnetic CuMnAs electrodes and the insulating GaP spacer. In particular we find that the torque remains staggered regardless of the termination, while the magnetoresistance depends on the microscopic details of the interface.

Graphene-based hybrid plasmonic waveguide with ultra long-ranged propagation length

We have investigated on a tunable graphene-based hybrid plasmonic terahertz waveguide with ultra-long-ranged propagation length at the frequency of 3 THz by using a finite-element method. The proposed structure consists of five graphene sheets, a curved semiconductor layer as a low-index material at the top of an air gap spacer, and gallium arsenide as a high-index material. The most important characteristic of this hybrid structure is its tunable, long-ranged propagation length. By tuning the waveguide dimensions, we can have a very long propagation length ranging from 20 to 15,000 μm, which is approximately 10 times higher than that in recently proposed structures. Moreover, we will show that with this increase in the propagation length, the normalized mode area does not change significantly and remains between 0.03% and 0.04%, indicating that this structure also poses a tight energy confinement.

Superhydrophobic condenser surfaces for air gap membrane distillation

Superhydrophobic surfaces for enhanced condensation in air gap membrane distillation (AGMD) may provide significantly improved distillate production rates and increased thermal efficiency. While AGMD is one of the most thermally efficient membrane distillation desalination configurations, large transport resistances in the air gap limit distillate production rates. AGMD experiments were performed with combinations of untreated, hydrophobic, and superhydrophobic condensation surfaces. A nanostructured copper oxide coated condensing surface produced durable 164°±4° contact angles and jumping droplet condensation. Tests were also performed on the air gap spacer, in this case a small diameter support mesh, to judge the effects of superhydrophobic treatment and conductivity on distillate production for AGMD. A novel visualization technique was implemented to see through PVDF membranes and confirm air gap behavior. The experiments were compared with numerical modeling of AGMD film-wise condensation and flooded-gap MD. The results indicate that the introduction of superhydrophobic surfaces can result in improvements in distillate production in excess of 60% over standard AGMD. However, for high distillate production, condensation on the superhydrophobic plate transitions from a partially wetted droplet morphology to Wenzel flooded (wetting) conditions. Mildly hydrophobic condensing surfaces were found to provide moderate improvement in distillate production. Superhydrophobic support meshes made a negligible difference in distillate production, but high conductivity support meshes showed significant increases in flux at the expense of increased conduction losses. The results outline recommended superhydrophobic condensation conditions at varied feed and cold side temperatures for substantial improvement to distillate production rate for AGMD systems in a flat plate configuration.

Monitoring the membrane scaling propensity of retentate in reverse osmosis desalination plants

Scaling appears first in the tail spiral wound membrane (SWM) elements of desalination plants due to increased salt concentration in the retentate; in particular, membrane scaling starts locally when supersaturation of sparingly soluble salts (commonly CaCO3 and CaSO4) is attained. Reliable determination of the onset of membrane scaling in the tail elements (as a function of the local retentate physico-chemical properties) provides a threshold condition serving a dual purpose; i.e., it imposes essentially an upper limit to the degree of permeate recovery, and guides the selection of an appropriate anti-scaling program involving additives. Judicious use of the latter is important for reduction of desalination cost and environmental impact. The current practices for estimating incipient scaling within the spacer filled reverse osmosis (RO) membrane elements involve a great deal of uncertainty. In this study, slightly supersaturated in CaCO3 brackish waters were desalinated in a test section comprising a narrow gap spacer filled channel simulating local (constant flux) conditions in SWM modules. Detailed data on incipient membrane scaling were obtained leading to the following main conclusions: (a) minute quantities of very small particles, ever present in RO plants, apparently promote heterogeneous nucleation; moreover, under the conditions tested, induction period for membrane scaling is practically nonexistent. (b) the initial scale deposit rates measured by special techniques (but undetectable with common bulk flow measurements) are substantial, and if not mitigated would be detrimental to SWM performance over a relatively short operating time period. (c) accurate determination of supersaturation ratio at the membrane surface Sw can be a reliable criterion for the onset of scaling, instead of currently used indices (e.g. Langelier Saturation Index) or practical type recommendations; a reliable method has been employed to determine Sw under local retentate conditions. Based on these results, a novel system was developed for monitoring the scaling propensity of retentate, which involves combination of a limited number of measurements in key locations of a RO plant, reliable algorithms for local equilibria and supersaturation (Sw) calculations, and a modern wireless electronic system for plant wide monitoring.

Laser dimpling and remote welding of zinc-coated steels for automotive applications

The flexibility in terms of beam shapebility and amplitude in the range of process parameters offered by the emerging high power and quality active fiber lasers can be advantageously used in overcoming the well-known problems in remote laser welding of zinc-coated steel components in the car mass production. The paper explores the potentiality offered by the combination of the scanner technology with high brilliance fiber lasers when laser dimpling and remote welding are executed in a successive order: the first one to realize gap spacers and the second one to weld together clamped sheets in zinc-coated steels. In particular, the substitution of the traditional mechanical dimpling with the laser dimpling is investigated in order to highlight the potentiality of a solution that is flexible, unaffected by tool wear and highly productive.

TFT-LCD中的液晶扩散研究

In order to improve the process and defect in ODF,the relationship between diffusion time and distance of liquid crystal in TFT-LCD(after vacuum alignment)is researched in this paper.A liquid crystal diffusion model of tilted state has been proposed by the assumption of newton fluid. Mathematical derivations prove that the flat state diffusion equation is a special case of tilted angle 0. The gravity effect becomes more significant by longer diffusion distance in titled state.That is why the diffusion time has difference between the two states.Panel size and LC pattern design have an effect on the final pattern of liquid crystal diffusion.Cell gap and photo spacer will affect the diffusion velocity.The effect can be reduced by more uniform gap and smaller density of spacer.Experimental studies show that the theoretical data calculated by the model is close to the experiment data.The model can make a good flow prediction for the diffusion of liquid crystal in TFT-LCD.

Influence of the End Ventilation Structure Change on the Temperature Distribution in the End Region of Large Water–Hydrogen–Hydrogen Cooled Turbogenerator

Flow network was built according to the ventilation structural characteristics of a 330 MW large water-hydrogen-hydrogen cooled turbogenerator. The variation of the fan inlet velocities, and the flow rates and pressures (boundary conditions) of each end region outlet were obtained, respectively, with different air gap spacer heights and different shelter board widths between the long press fingers by flow network method, and the relative law was analyzed. In order to study the influence of the changed end ventilation structures on the temperature distribution of the end parts, 3-D transient electromagnetic field in the turbogenerator end was calculated, and the eddy current losses (heat sources) of the end parts were gained by the finite-element method. Meanwhile, the fluid and thermal mathematics and physical models of the end region were given. Using the finite-volume method, the influence of the changed end ventilation structures on the surface heat transfer coefficient and the temperature of end parts was researched. It shows that the proper changes in the air gap spacer height and shelter board width decrease the copper shield temperature and result in a reasonable temperature distribution in the end parts. It provides the useful reference for the further design of the large turbogenerators.

HAVAR

Abstract Havar is a heat-treatable cobalt-base alloy that provides very high strength. The alloy has excellent comsion resistance and is nonmagnetic. Applications include pressure diaphragms. power springs, gap spacers in magnetic heads, and target foils in nuclear physics. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Co-24. Producer or source: Hamilton Precision Metals.

Micromegas prototypes with thermo-bond film separators

In this paper we report the results of Micromegas prototypes constructed by attaching micromesh to an anode using thermo-bond films. The excellent metal attaching ability and good dielectical property of this kind of film make it a promising material to be used as avalanche gap spacers. Several prototypes are successfully made. The electron transmission properties are first studied and then the gas gain is measured in argon-isobutane mixtures. The maximum gain of more than 104 is easily obtained. The energy resolutions for 55Fe 5.9 keV Kα ray can be better than 20% over one magnitude in gain for different operational gas mixtures and the best energy resolution of 13.7% (FWHM) can be achieved with the gas mixture of 94% argon concentration. The preliminary test results of the prototypes with sensitive area of 45 mm×45 mm without internal support show good uniformity across the sensitive area.