Symmetric Silicon Research Articles

Interfacial microstructure and synergistic enhancement mechanism of symmetric gradient SiCp-reinforced aluminum matrix sandwich structure

Inspired by the biological sandwich structure to achieve excellent mechanical properties with both high strength and high ductility, the symmetric gradient silicon carbide particles (SiCp) reinforced aluminum (Al) composites, consisting of 10 % SiCp/Al-3% SiCp/Al-Al-3% SiCp/Al-10 % SiCp/Al, was fabricated using spark plasma sintering technology. The flat interface was achieved through hot rolling, significantly improving the bonding of interlayers. The differences in SiCp content among layers led to distinct evolution patterns in microstructure. In the pure Al layer, a notable continuous recrystallization mechanism was observed, while in the 3 % SiCp/Al and 10 % SiCp/Al layers, the recrystallization mechanism was nucleation-growth. The transmission electron microscope results indicated that the hindrance of dislocation motion at the interlayer interface and SiCp-Al interface enhanced the dislocation density, thereby improving its plastic deformation capability. On the other hand, the deflection and passivation of cracks at the interlayer interface significantly improves toughness. The differences intragranular strain among layers were most pronounced at the interlayer interfaces, leading to them becoming the stress concentration zone. Uncoordinated plastic deformation leads to sequential failure of layers, vertical cracks first occurred in the 10 % SiCp/Al layer, then propagated towards the interlayer interface and the 3 % SiCp/Al layer, respectively.

Strain-Induced Frequency Splitting in PT Symmetric Coupled Silicon Resonators.

When two resonators of coupled silicon resonators are identical and the gain on one side is equal to the loss on the other side, a parity-time (PT) symmetric-coupled silicon resonator is formed. As non-Hermitian systems, the PT-symmetric systems have exhibited many special properties and interesting phenomena. This paper proposes the strain-induced frequency splitting in PT symmetry-coupled silicon resonators. The frequency splitting of the PT system caused by strain perturbations is derived and simulated. Theory and simulation both indicate that the PT system is more sensitive to strain perturbation near the exceptional point (EP) point. Then, a feedback circuit is designed to achieve the negative damping required for PT symmetry. Based on a simple silicon-on-insulator (SOI) process, the silicon resonator chip is successfully fabricated. After that, the PT-symmetric-coupled silicon resonators are successfully constructed, and the frequency splitting phenomenon caused by strain is observed experimentally.

Symmetric silicon microring resonator optical crossbar array for accelerated inference and training in deep learning

Photonic integrated circuits are emerging as a promising platform for accelerating matrix multiplications in deep learning, leveraging the inherent parallel nature of light. Although various schemes have been proposed and demonstrated to realize such photonic matrix accelerators, the in situ training of artificial neural networks using photonic accelerators remains challenging due to the difficulty of direct on-chip backpropagation on a photonic chip. In this work, we propose a silicon microring resonator (MRR) optical crossbar array with a symmetric structure that allows for simple on-chip backpropagation, potentially enabling the acceleration of both the inference and training phases of deep learning. We demonstrate a 4×4 circuit on a Si-on-insulator platform and use it to perform inference tasks of a simple neural network for classifying iris flowers, achieving a classification accuracy of 93.3%. Subsequently, we train the neural network using simulated on-chip backpropagation and achieve an accuracy of 91.1% in the same inference task after training. Furthermore, we simulate a convolutional neural network for handwritten digit recognition, using a 9×9 MRR crossbar array to perform the convolution operations. This work contributes to the realization of compact and energy-efficient photonic accelerators for deep learning.

Perfect absorber based on symmetric square silicon grating with polarization and angular stability using particle swarm optimization algorithm

Perfect absorber based on symmetric square silicon grating with polarization and angular stability using particle swarm optimization algorithm

Quasi-symmetry-protected BICs in a double-notched silicon nanodisk metasurface.

Bound states in the continuum (BICs) hold great promise in enhancing light-matter interaction as they have an infinite Q-factor. To date, the symmetry-protected BIC (SP-BIC) is one of the most intensively studied BICs because it is easily found in a dielectric metasurface satisfying certain group symmetry. To convert SP-BICs into quasi-BICs (QBICs), structural symmetry shall be broken so that external excitation can access them. Usually, the unit cell's asymmetry is created by removing or adding parts of dielectric nanostructures. The QBICs are usually excited only by s-polarized or p-polarized light because of the symmetry-breaking of the structure. In this work, we investigate the excited QBIC properties by introducing double notches on the edges of highly symmetrical silicon nanodisks. The QBIC shares the same optical response under the s-polarized and p-polarized light. The effect of polarization on coupling efficiency between the QBIC mode and incident light is studied, and the highest coupling efficiency occurs at a polarization angle of 135 ∘, which corresponds to the radiative channel. Moreover, the near-field distribution and multipole decomposition confirm that the QBIC is dominated by the magnetic dipole along the z direction. It is noted that the QBIC covers a wide spectrum region. Finally, we present an experimental confirmation; the measured spectrum shows a sharp Fano resonance with a Q-factor of 260. Our results suggest promising applications in enhancing light-matter interaction, such as lasing, sensing, and nonlinear harmonic generation.

Structural Fusion Yields Guest Acceptors that Enable Ternary Organic Solar Cells with 18.77 % Efficiency

AbstractThe design and selection of a suitable guest acceptor are particularly important for improving the photovoltaic performance of ternary organic solar cells (OSCs). Herein, we designed and successfully synthesized two asymmetric silicon–oxygen bridged guest acceptors, which featured distinct blue‐shifted absorption, upshifted lowest unoccupied molecular orbital energy levels, and larger dipole moments than symmetric silicon–oxygen‐bridged acceptor. Ternary devices with the incorporation of 14.2 wt % these two asymmetric guest acceptors exhibited excellent performance with power conversion efficiencies (PCEs) of 18.22 % and 18.77 %, respectively. Our success in precise control of material properties via structural fusion of five‐membered carbon linkages and six‐membered silicon–oxygen connection at the central electron‐donating core unit of fused‐ring electron acceptors can attract considerable attention and bring new vigor and vitality for developing new materials toward more efficient OSCs.

A Review of Symmetric Silicon MEMS Gyroscope Mode-Matching Technologies.

The symmetric MEMS gyroscope is a typical representative of inertial navigation sensors in recent years. It is different from the traditional mechanical rotor gyroscope in that it structurally discards the high-speed rotor and other moving parts to extend the service life and significantly improve accuracy. The highest accuracy is achieved when the ideal mode-matching state is realized. Due to the processing limitation, this index cannot be achieved, and we can only explore ways to approach this index continuously. This paper’s results of error suppression for the symmetric MEMS gyroscope are initially classified into three categories. The first category mainly introduces the processing structure and working mode of the symmetrical gyroscope. The second is mechanical tuning from the structure and the third is electrostatic tuning from the peripheral control circuit. Based on the listed results, the paper compares the two tuning modes and analyzes their advantages and disadvantages. The fourth category is the tuning means incorporating the emerging algorithm. On this basis, the elements of improvement for future high-precision symmetric MEMS gyroscopes are envisioned to provide a part of the theoretical reference for the future development direction of sensors in inertial navigation.

An RHCP and LHCP polarization reconfigurable microstrip antenna for ISM band smart city applications

Abstract In this article, a microstrip antenna having circular polarization switching capability is presented. This antenna consists of a circular-shaped radiating patch with a single co-axial probe feed line. The polarization reconfigurability is achieved by introducing four symmetrical U-shaped slots and silicon PIN diodes on the radiating patch. A prototype of the design is fabricated on an FR-4 substrate with overall dimension of 70 × 70 × 1.6 mm to verify the performances. The measured results of the antenna exhibit an impedance bandwidth (S 11 < −10 dB) of 5% in the frequency range of 2.37–2.49 GHz. The maximum gain of the antenna is found to be 2.99 dBic at 2.43 GHz. The antenna shows stable radiation performances at 2.4 GHz with 4.1% of 3-dB axial ratio bandwidth, and more than 105° of 3-dB axial ratio beamwidth for both right-hand circular polarization and left -hand circular polarization which make it suitable for ISM band Smart city applications.

Novel axially symmetric and unsymmetric silicon(IV) phthalocyanines having anti-inflammatory groups: synthesis, characterization and their biological properties.

New asymmetric Si(IV)Pc (1), monomeloxicammonotriethyleneglycolmonomethylether (phthalocyaninano)silicone, axially ligated with meloxicam as a non-steroidal anti-inflammatory drug (NSAID), or triethylene glycol monomethyl ether and symmetric Si(IV)Pc (2), diclofenac(phthalocyaninano)silicone, axially ligated with two diclofenac as NSAID, were synthesized and characterized as antioxidant and antimicrobial agents together with polyoxo-SiPc (3), ditriethyleneglycolmonomethylether(phthalocyaninano)silicone, and SiPc(OH)2 (4), dihydroxy(phthalocyaninano)silicone. The photophysical and photochemical properties of these compounds were investigated. Then, antioxidant assays, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferrous ion chelating activities, were performed for these Si(IV) phthalocyanine derivatives (1, 2, 3 and 4). The highest DPPH scavenging activity of 73.48% was achieved with compound 2 and the highest ferrous chelating ability of 66.42% was obtained with compound 3. The results of the antioxidant assays indicated that Pc derivatives 1, 2 and 3 have remarkable superoxide radical scavenging activities, and moderate 2,2-diphenyl-1-picrylhydrazyl activities and metal chelating activities. The antimicrobial effects of the Si(IV) phthalocyanine compounds were studied against six pathogenic bacteria and two pathogenic microfungi. The results for the antimicrobial activity of these compounds indicated that Enterococcus faecalis (ATCC 29212) was the most sensitive microorganism and Pseudomonas aeruginosa (ATCC 27853) and Legionella pneumophila subsp. pneumophila (ATCC 33152) were the most resistant microorganisms against the tested compounds. The DNA cleavage ability and microbial cell viability of these compounds were studied. The studied compounds demonstrated excellent DNA nuclease activity and exhibited 100% cell viability inhibition at 500 mg L-1. Also, the antimicrobial photodynamic therapy of the compounds was tested against Escherichia coli (ATCC 25922) and significant photodynamic antimicrobial activity was observed. In addition, the effect of phthalocyanines on biofilm inhibition produced by Staphylococcus aureus (ATCC 25923) was also tested and 3 showed excellent biofilm inhibition of 82.14%.

A Bifunctional Silicon Dielectric Metasurface Based on Quasi-Bound States in the Continuum.

Quasi-bound states in the continuum provide an effective and observable way to improve metasurface performance, usually with an ultra-high-quality factor. Dielectric metasurfaces dependent on Mie resonances have the characteristic of significantly low loss, and the polarization can be affected by the parameter tuning of the structure. Based on the theory of quasi-bound states in the continuum, we propose and simulate a bifunctional resonant metasurface, whose periodic unit structure consists of four antiparallel and symmetrical amorphous silicon columns embedded in a poly(methyl methacrylate) layer. The metasurface can exhibit an extreme Huygens’ regime in the case of an incident plane wave with linear polarization, while exhibiting chirality in the case of incident circular polarized light. Our structure provides ideas for promoting the multifunctional development of flat optical devices, as well as presenting potential in polarization-dependent fields.

Deep isotropic chemical etching (DICE) process for fabricating highly symmetric hemispherical silicon molds

This paper introduces the deep isotropic chemical etching (DICE) process developed for wafer-scale manufacturing of highly symmetric hemispherical silicon molds. The DICE process uses silicon nitride concentric rings as a masking layer during hydrofluoric, nitric, acetic etching of silicon substrate. These concentric rings pop up and widen the etch aperture as etch depth increases, thereby allowing control of vertical and lateral etch rates until reaching the desired mold dimensions. Our comparative experiments demonstrate that the pop-up rings are remarkable at creating molds with enhanced symmetry compared to the conventional pinhole masks. We have demonstrated the effectiveness of our approach compared to single pinholes by producing a super-symmetric 0.1 mm hemispherical mold () using two concentric rings surrounding a pinhole. We have then shown how the DICE process can be used to fabricate larger silicon molds and presented the results of a single concentric ring that achieves fabrication of a 0.25 mm-deep mold with an aspect ratio of .

Design of Narrow-Band Absorber Based on Symmetric Silicon Grating and Research on Its Sensing Performance

In this paper, using the surface plasmon and Fabry–Pérot (FP) cavity, the design of a symmetric silicon grating absorber is proposed. The time-domain finite difference method is used for simulation calculations. The basic unit structure is a dielectric grating composed of silicon dioxide, metal and silicon. Through the adjustment of geometric parameters, we have achieved the best of the symmetric silicon grating absorber. A narrowband absorption peak with an absorption rate greater than 99% is generated in the 3000–5000 nm optical band, and the wavelength of the absorption peak is λ = 3750 nm. The physical absorption mechanism is that silicon light generates surface plasmon waves under the interaction with incident light, and the electromagnetic field coupling of surface plasmon waves and light causes surface plasmon resonance, thereby exciting strong light response modulation. We also explore the influence of geometric parameters and polarization angle on the performance of silicon grating absorbers. Finally, we systematically study the refractive index sensitivity of these structures. These structures can be widely used in optical filtering, spectral sensing, gas detection and other fields.

Improved short channel electrostatics through design of partially junction-less double-gate MOSFETs

Quantum confinement effects tend to diminish gate control over the channel, further degrading the channel electrostatics of short channel Double-Gate (DG) Silicon-on-Insulator (SOI) MOSFETs. In this work, we first design an n-channel Junction-less (JL) DG MOSFET with a channel length (Lg) of 10 nm, where the source/drain doping, determined through Technology Computer-Aided Design (TCAD) simulations, enables better gate control for different channel thicknesses (tch) and oxide thicknesses (tox). The source/drain doping, thus determined, enables JL DG MOSFETs to overcome quantum confinement effects while also achieving key ITRS (International Technology Roadmap for Semiconductors) targets in terms of sub-threshold slope (S) and threshold voltage (Vth). We then introduce a heavily doped symmetric p-type silicon layer at the interface of the channel region with the top/bottom oxide such that the thickness and doping of the p-type layer enable tuning of the threshold voltage. In this partially JL DG MOSFET, by replacing the n-type doped silicon with n-type silicon–germanium (Si0.7Ge0.3) of lower doping, determined through TCAD simulations, we continue to demonstrate excellent channel electrostatics (ITRS targets) at short channel lengths (Lg = 10 nm) over a wide range of channel and oxide thicknesses while also showing enhanced strong inversion channel currents.

Polarization independent enhancement of zeroth order diffracted second harmonic from multilayer gallium selenide on a silicon resonant metasurface.

We demonstrate polarization-independent resonant-enhancement of second harmonic generation (SHG) from multilayer Gallium Selenide (GaSe) on a silicon-based resonant metasurface. Two-dimensional hexagonal photonic lattice with circularly symmetric silicon meta-atoms are designed to achieve resonant field enhancement at the fundamental wavelength independent of the incident polarization direction. Such structures are however found to exhibit strong resonant field depolarization effects at the fundamental excitation fields resulting in modified nonlinear polarization components when compared to the native GaSe layer. Furthermore, the sub-wavelength metasurface designed to have resonances at the fundamental wavelengths act as a higher order diffraction grating at the second harmonic wavelength. Nonlinear wave propagation simulations show that the higher order diffracted SHG exhibit strong polarization dependent enhancement with characteristics very different from the native GaSe layer. In this context, polarization independent enhancement of the second harmonic signal is achieved only for the zeroth order diffracted component. Experimental study of second harmonic generation from the GaSe layer integrated with the silicon metasurface shows maximum nonlinear signal enhancement on-resonance with polarization dependence identical to the native GaSe layer by selectively detecting the zeroth-order diffracted component. This work shows that it is not sufficient to use symmetric meta-atoms in such 2D material integrated resonant metasurfaces for achieving polarization independent nonlinear optical enhancement. Depolarization of the resonant fields and higher-order diffraction at the nonlinear signal wavelength need to be considered as well.

Bent silicon slot waveguides with both low loss and low nonlinearity

With the development of highly integrated linear optical systems, both low loss and low nonlinearity are demanded for silicon slot waveguides with a small bending radius. In this paper, we calculate the variations of loss and nonlinearity with the bending radius of air-cladding and silica-cladding slot waveguides, and the mechanisms underlying the variations are revealed. We show that slot waveguides with symmetric silicon arms cannot possess low nonlinearity and low loss simultaneously due to the serious optical power leakage to the substrate. To solve this issue, asymmetric silicon arms are employed. By increasing the width of the inner arm, the high power confinement in the slot can be ensured, and this also makes the simultaneous low loss and low nonlinearity possible. We show that the silica-cladding slot waveguide under a 5 μm radius can obtain power confinement, loss and nonlinearity as respectively 40%, 1.17 × 10−4 dB/μm and 16.41/W/m, which are all comparable with those in the straight slot waveguide.

Stereoselective Synthesis of Cis- and Trans-Tetrasubstituted Vinyl Silanes Using a Silyl-Heck Strategy and Hiyama Conditions for Their Cross-Coupling.

We report a palladium-catalyzed, three-component carbosilylation reaction of internal symmetrical alkynes, silicon electrophiles, and primary alkyl zinc iodides. Depending on the choice of ligand, stereoselective synthesis of either cis- or trans-tetrasubstituted vinyl silanes is possible. We also demonstrate conditions for the Hiyama cross-coupling of these products to prepare geometrically defined tetrasubstituted alkenes.

Characteristics of electric quadrupole and magnetic quadrupole coupling in a symmetric silicon structure

Multipole interferences have attracted a lot of interests in last decade due to extraordinary performance on beam control and scattering shaping. However, most of previous works focused on the dipole-based interferences while the quadrupole modes and other high-order multipole modes with unique properties were of less attention. In this work, we aim to expand the present dipole-based multipole-interference regime to the quadrupole-interference regime. We study the interference between an electric quadrupole (EQ) and a magnetic quadrupole (MQ) in both isolated and periodically arranged homogeneous cross dielectric structure. Through structural parametric control, the EQ and MQ can be precisely tuned to share the same resonant intensity at a specific wavelength, resulting in a generalized Kerker effect. Moreover, a dark MQ mode, which is orthogonal with the original MQ mode, arises when we increase the interaction between structure. We find that the spectral approaching between dark MQ and original bright EQ results in an EIT effect and Fano-shaped spectral reflection response. The induced Fano spectrum possesses tunable quality factors varying from ∼10 to >105 with the variation of EQ–MQ coupling efficiency. The numerically derived maximum quality factor (238, 618) of the dielectric EQ–MQ coupling system even exceeds the quality factors of many plasmonic resonant systems. We also prove that such spectrum can be adopted to refractive index sensing. Besides, we show that EQ–MQ coupling can bring about rapid 2π phase change, which can be applied in metasurface designs. These results and conclusions about the EQ–MQ interference systems can provide a promising avenue for advanced optical devices.

Limitation in Controlling the Morphology of Mammalian Vero Cells Induced by Cell Division on Asymmetric Tungsten-Silicon Oxide Nanocomposite.

Engineered nanomaterials are often used in tissue engineering applications to influence and manipulate the behavior of cells. Recently, a number of tungsten-silicon oxide nanocomposite devices containing equal width (symmetric) tungsten and silicon oxide parallel line comb structures were developed and used by our group. The devices induced over 90% of seeded cells (Vero) to align within ±20° of the axes of 10 µm wide tungsten lines. Furthermore, a mathematical model was successfully developed to predict this alignment behavior and forecast the minimum width of isolated tungsten lines required to induce such behavior. However, the mechanism by which the widths of the symmetrical tungsten and silicon oxide lines induce the alignment behavior is still unknown. Furthermore, the model was never tested on more complex asymmetrical structures. Herewith, experiments were conducted with mammalian cells on complex asymmetrical structures with unequal tungsten and silicon oxide line widths. Results showed that the model could be extended to more complex pattern structures. In addition, cell morphology on the patterned structures reset during cell division because of mitotic rounding, which reduced the population of cells that elongated and aligned on the tungsten lines. Ultimately, we concluded that it was impossible to achieve a 100% alignment with cells having unsynchronized cell cycles because cell rounding during mitosis took precedence over cell alignment; in other words, internal chemical cues had a stronger role in cell morphology than external cues.

Influence of Room Temperature Sputtered Al-Doped Zinc Oxide on Passivation Quality in Silicon Heterojunction Solar Cells

Al-doped zinc oxide (AZO) is a potential candidate to substitute tin-doped indium oxide in silicon heterojunction (SHJ) solar cells due to its low cost and low ecological impact. The AZO, sputtered at room temperature (RT), is of particular interest because of low thermal budget and potential for high throughput production with the well-established industrial methods. In SHJ solar cells, high effective carrier lifetime prerequisite for the high open-circuit voltage is achieved with surface passivation by intrinsic amorphous silicon layers followed by doped silicon layers. The passivation quality may be affected by the subsequent sputtering of an AZO layer especially at RT. In this article, we investigated the influence of the AZO sputtering and postdeposition annealing on the effective carrier lifetime in symmetrical silicon layer stacks with n- or p-type doped silicon layers and solar cell precursors. It has been found that the effective carrier lifetime significantly decreased after AZO sputtering at RT. The detrimental effect of AZO sputtering is substrate temperature dependent and is smaller or even absent at elevated temperatures. However, postdeposition annealing, equivalent to the Ag paste curing, mostly recovered the effective carrier lifetime in the symmetrical stacks as well as in the cell precursors. Finally, an aperture area efficiency of 21.2% has been achieved for the 19 mm × 19 mm SHJ solar cell prepared with room temperature sputtered AZO.

Improved HNA isotropic etching for large-scale highly symmetric toroidal silicon molds with <10-nm roughness

Microsystem technology is well suited to batch fabricate microhemispherical resonator gyroscopes (HRG) to reduce cost and volume. In the processing of micro-HRG, a crucial step is to get a 3-D hemispherical mold with the large-scale, high-symmetry, and smooth surface. Compared with the hemispherical resonator, the toroidal resonator has the smaller frequency split and larger effective resonance mass under the same processing accuracy. A wafer-scale etching method for the toroidal resonator mold was presented, which is based on the deep reactive ion etching and improved HNA isotropic etching. The advantages of this method include low cost, time savings, and easy operation. With this method, toroidal molds with an average diameter over 1900 μm, asymmetry