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In thin film deposition, Ar/SiH4 mixtures are widely used to make polysilicon (poly-Si) and hydrogenated amorphous silicon (a-SiH) layers. Despite extensive research conducted on this mixture, little research has focused on the variations in plasma properties, radicals, and ions that occur during plasma discharge in inductively coupled plasma (ICP) equipment compared to capacitive coupled plasma equipment. In this paper, we investigate the properties of the plasma generated through mathematical modeling of Ar/SiH4 inductive coupled plasma discharge by using the electron energy distribution function (EEDF) obtained by solving the Boltzmann equation. We closely examine the variation in plasma properties and the correlation of plasma variables by controlling the radio frequency power and gas pressure during the process conditions. The Boltzmann equation was computed by assuming the two-term approximation, resulting in a Druyvesteyn-like EEDF due to the high-pressure conditions. To validate the simulation model, the 2D simulation results were compared with probe measurements performed in a two-turn ICP chamber. The results demonstrated encouraging agreement with the measured data. This research not only enhances our comprehension of the discharge characteristics but also establishes a framework for optimizing the discharge conditions to enhance the process and effectively regulate external variables. [ABSTRACT FROM AUTHOR]

The spectrum of localized hole states (traps) in amorphous silicon nitride, a-Si3N4, is experimentally studied using the method of thermally stimulated depolarization. The experiment is compared with theoretical calculations using three models of the energy spectrum of traps: discrete spectrum (monoenergetic trap), continuous spectrum, and Gaussian trap distribution. The experiment is quantitatively described by a model of a discrete spectrum of traps with an energy of 1.15 eV and a width of no more than 0.01 eV. In the case of a continuous and Gaussian spectrum of traps, the contribution to depolarization is made by the deepest traps. The blurring of the trap energy level in a-Si3N4 due to the absence of long-range order (fluctuations in the Si–N bond length and fluctuations in the N–Si–N and Si–N–Si angles) does not exceed 0.01 eV. [ABSTRACT FROM AUTHOR]

Thin films of amorphous silicon (a-Si) coated on metals such as nickel (Ni) are one of the most promising anode architectures for high-energy-density lithium-ion (Li-ion) batteries. The performance and longevity of batteries with this type of electrode depend on the integrity of the Ni/a–Si interface. The integrity of the a-Si /Ni bonded interface during cycling is critical, but the experimental characterization of interfacial failure of this material system is highly challenging and there is a sparsity of interface strength data in the literature. Here, we describe a laser spallation (LS) technique to characterize the interfacial adhesion strength of Ni/a–Si multilayer films created by chemical vapor deposition (CVD). The LS technique enables the non-contact measurement of the tensile interfacial strength with high precision when compared to conventional methods for characterizing adhesion. Interferometric measurement combined with finite element analysis shows that the Ni/a–Si interface, created via the CVD of a-Si on Ni surfaces can withstand ≈46–72 MPa in tension before failure initiation. To ensure successful and precise characterization of interfacial adhesion strength using LS, we further develop a design criterion for multi-layer samples by analyzing the thin-film mechanics. Our study provides insights into the strength of the Ni/a–Si interface that governs the performance and durability of high-energy-density anodes and offers design guidelines for improving thin-film electrode integrity. [ABSTRACT FROM AUTHOR]

We show that the micro-scale variations in the relaxation state of amorphous silicon (a-Si) can be well-identified by Raman mapping over hundreds or thousands of μm2 in 1–2 h. Pure and relaxed a-Si is obtained by self-implantation in crystalline silicon (c-Si) followed by anneal at 500 °C. It is then locally re-implanted over micro-sized patterns to produce unrelaxed a-Si zones. Raman mappings are obtained by pointwise confocal μ-Raman and hyperspectral Raman imaging. We also measure the depth profiles of the relaxation state in re-implanted a-Si by scanning the edge of a re-implanted sample. We infer from the depth profiles that the minimal damage dose to fully de-relax a-Si is 0.04 displacements per atoms, which is an order of magnitude smaller than the fluence needed to fully amorphize c-Si. [ABSTRACT FROM AUTHOR]

The ability to spatially resolve the carrier mobility profile along the cross section of micrometer-thin solar cells is vital, both for fundamental studies in photovoltaics and as quality control for reproducibly obtaining high conversion efficiencies in commercial solar cell modules. Presently, no technique capable of such an endeavor is available to the best of our knowledge. Here, we introduce a novel method capable of profiling the carrier mobility along the z axis in thin-film photovoltaics. Our setup is based on the integration of photogenerated charge extraction by linearly increasing voltage (p-CELIV) with a scanning confocal optical microscope (SCOM) toward a confocal and cross-sectional p-CELIV (cs-p-CELIV) system. As monomolecular recombination of excess carriers is the most frequent radiative pathway for electrons and holes in solar cells at low power density of illumination, while multimolecular recombination dominates at high power, enhanced multimolecular recombination occurs at the SCOM focal plane. Thus, the cs-p-CELIV signal provides enhanced information on the mobility of all of the cross-sectional layers except the focal plane. By scanning the focal plane along the z axis, the mobility profile can be derived. To demonstrate our technique, we use it to investigate the carrier mobility in three hydrogenated amorphous silicon (a-Si:H) solar cells. The mobility profiles obtained by cs-p-CELIV correlate well with well-known depletion layer effects and the H content profile in a-Si:H, which is measured independently. Our findings are in excellent agreement with models suggesting a critical role of Si–H bonding in locally determining the carrier mobility in a-Si:H. [ABSTRACT FROM AUTHOR]

Fabrication of dielectrics at low temperature is required for temperature-sensitive detectors. For superconducting detectors, such as transition edge sensors and kinetic inductance detectors, AlMn is widely studied due to its variable superconducting transition temperature at different baking temperatures. Experimentally only the highest baking temperature determines AlMn transition temperature, so we need to control the wafer temperature during the whole process. In general, the highest process temperature happens during dielectric fabrication. Here, we present the cryogenic microwave performance of Si 3 N 4 , SiN x and α -Si using ICPCVD at low temperature of 75 ∘ C. The dielectric constant, internal quality factor and TLS properties are studied using Al parallel plate resonators. [ABSTRACT FROM AUTHOR]

Diamond‐like carbon (DLC) is an amorphous material widely used in industrial applications due to its chemical, mechanical, and tribological properties and, also, for decorative purposes. However, its low adhesion to ferrous alloys reduces its effectiveness in certain applications, necessitating the use of adhesion interlayers to reduce stresses at the interfaces and enhance the density of strong bonds. In this context, the factors that promote good adhesion in this system and specify the parameters must be understood in detail. Thus, the present study aims to assess the influence of the base pressure on the deposition of an amorphous silicon carbide adhesion interlayer between DLC coating and a ferrous alloy substrate. Microstructural, physicochemical, morphological, and mechanotribological analyses were conducted to understand the adhesion behavior in terms of structural and chemical aspects. In addition to the influence of the interlayer thickness, the elemental Si/C ratios and the relative oxygen content have an impact on the maximum load supported by the coatings, as well as the different delamination mechanisms generated in adhesion tests. [ABSTRACT FROM AUTHOR]

This work presents the polarization‐dependent behavior of the anapole state in stacked amorphous silicon (a‐Si) nanodisks with elliptical geometries. Using SiO2 as a spacer layer between the a‐Si disks, the high index contrast between these materials can be used to significantly reduce the fabrication complexity of the system compared to traditional methods that require additional etching of the spacers. A novel way of continuous tuning of the electric dipole anapole excitation within elliptical stacked a‐Si nanoresonators is demonstrated. By rotating the incident electric field's polarization angle, the anapole state can be selectively excited at two distinct wavelength positions separated by 80 nm. Experimental results show characteristic dips in the reflectance of the fabricated elliptical a‐Si stacks with wavelength positions between 1135 and 1217 nm depending on the polarization angle of the incident field which is corroborated by FDTD simulations. Through simulating the internal electric field in the resonators and using multipole decomposition, it is shown that the reflectance dips are due to anapole excitation in the individual disks. The capability to excite anapoles at two distinct wavelengths in the same structure has promising implications for the development of tunable sensors, frequency converters, and quantum memory applications. [ABSTRACT FROM AUTHOR]

This study introduces an innovative approach to pressure sensing in sports training using amorphous silicon nanostructure-based sensors. These sensors demonstrated high sensitivity (0.75 Ω/kPa) and a broad pressure detection range (1–100 kPa), making them ideal for capturing the nuances of athletic movements. Their compact size (5 mm×5 mm) and superior durability (over 5000 cycles with minimal performance variation) allowed for seamless integration into athletic shoes and attire. The sensors effectively captured pressure patterns in running, such as heel strikes peaking at 300 kPa, and cycling, revealing a 200 kPa increase in the perineal region during posture shifts. Comparative analysis highlighted the advantages of amorphous silicon nanostructure sensors over existing technologies, including higher sensitivity, wider pressure range, smaller size, and better durability. The integration of these sensors provided invaluable data for optimizing training regimes and preventing injuries. The study also delved into the physical and chemical characterization of the nanostructures, confirming their uniform size distribution, surface morphology, and amorphous nature, which contributed to their exceptional sensing performance. The findings underscore the immense potential of amorphous silicon nanostructure sensors in revolutionizing athletic performance analysis and injury prevention, offering a significant upgrade over current technologies in terms of accuracy, adaptability, and user-friendliness. This research paves the way for more sophisticated, precise, and athlete-centric pressure sensing solutions, transforming the landscape of sports technology and biomechanical assessment. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study of hydrogenated amorphous silicon (a-Si)-based detectors, utilizing electrical characterization, Raman spectroscopy, photoemission, and inverse photoemission techniques. The unique properties of a-Si have sparked interest in its application for radiation detection in both physics and medicine. Although amorphous silicon (a-Si) is inherently a highly defective material, hydrogenation significantly reduces defect density, enabling its use in radiation detector devices. Spectroscopic measurements provide insights into the intricate relationship between the structure and electronic properties of a-Si, enhancing our understanding of how specific configurations, such as the choice of substrate, can markedly influence detector performance. In this study, we compare the performance of a-Si detectors deposited on two different substrates: crystalline silicon (c-Si) and flexible Kapton. Our findings suggest that detectors deposited on Kapton exhibit reduced sensitivity, despite having comparable noise and leakage current levels to those on crystalline silicon. We hypothesize that this discrepancy may be attributed to the substrate material, differences in film morphology, and/or the alignment of energy levels. Further measurements are planned to substantiate these hypotheses. [ABSTRACT FROM AUTHOR]

In most optical waveguides employed within photonic integrated circuits, light confinement is achieved by etching the high-index layer. However, these waveguides often lack versatility in optimizing optical properties, such as mode size, shape, dispersion, and polarization. Moreover, they frequently suffer from high coupling losses and their propagation losses are significantly influenced by the quality of the etching process, especially for materials with high mechanical rigidity. Here, we present a hybrid optical waveguide concept that effectively addresses these limitations by combining a strip of easily processible low-index material (SU8) with a high-index hard-to-etch guiding layer (amorphous silicon carbide, SiC). Our approach not only eliminates the need for SiC etching but also offers flexibility in waveguide design to accommodate advanced functionalities. One of the key advancements of this hybrid configuration is its ability to suppress the transverse magnetic mode by 62 dB at 1550 nm, effectively functioning as a transverse electric pass waveguide. This simplifies the measurements by eliminating the need for polarization controllers and polarizers. Furthermore, through tailored waveguides, we achieve 2.5 times higher coupling efficiency compared to untapered hybrid SiC waveguides. We also demonstrate that thermal baking of the polymer layer reduces the scattering losses from 1.57 to 1.3 dB/cm. In essence, our hybrid approach offers a versatile way of realizing low-loss SiC-based integrated optical components with advanced features, such as excellent polarization suppression, flexible mode shapes, and dispersion control, compared to etched counterparts. [ABSTRACT FROM AUTHOR]

This paper presents a multifunctional tuneable wideband metasurface absorber based on phase-changing Vanadium dioxide (VO2). The 'quad isotropic VO2 circular sectors' are constructed on amorphous silicon dioxide (SiO2), backed with 0.2 µm-thick gold layer to design the proposed absorber. This novel wideband tunable structure can independently be used as a reflector and absorber as an EMI shield; hence, this multi-functionality in a single structure proves novel and unique in the terahertz frequency range. This unit cell offers a bandwidth of 3.5 THz with more than 90% of absorptivity under normal wave incidence. The equivalent circuit model, surface currents, and field distributions are further investigated to provide a better understanding of structural evolution. Moreover, a wideband absorption has been observed up to the 60° incident angle for both the transverse modes, showing a polarization-insensitive behavior due to the symmetricity in the structure. The parametric study explores, optimizes, and demonstrates various other main characteristics and parameters of the proposed absorber. The novel structure offers shielding effectiveness (SE) higher than 40 dB throughout the frequency band under both normal and oblique incidence. This outstanding performance makes it a strong contender for EMI-EMC applications. Furthermore, it shows great potential in the field of terahertz technology, such as terahertz imagers, detectors, sensors, and other wideband applications. [ABSTRACT FROM AUTHOR]

Photonic circuits find applications in biomedicine, manufacturing, quantum computing and communications. Photonic waveguides are crucial components, typically having cross-section orders of magnitude inferior when compared with other photonic components (e.g., optical fibers, light sources and photodetectors). Several light-coupling methods exist, consisting of either on-plane (e.g., adiabatic and end-fire coupling) or off-plane methods (e.g., grating and vertical couplers). The grating coupler is a versatile light-transference technique which can be tested at wafer level, not requiring specific fiber terminations or additional optical components, like lenses, polarizers or prisms. This study focuses on fully-etched grating couplers without a bottom reflector, made from hydrogenated amorphous silicon (a-Si:H), deposited over a silica substrate. Different coupler designs were tested, and of these we highlight two: the superimposition of two lithographic masks with different periods and an offset between them to create a random distribution and a technique based on the quadratic refractive-index variation along the device's length. Results were obtained by 2D-FDTD simulation. The designed grating couplers achieve coupling efficiencies for the TE-like mode over −8 dB (mask overlap) and −3 dB (quadratic variation), at a wavelength of 1550 nm. The coupling scheme considers a 220 nm a-Si:H waveguide and an SMF-28 optical fiber. [ABSTRACT FROM AUTHOR]

In recent years, the charge carrier mobility study of organic semiconductors has seen significant progress and surpassed that of amorphous silicon thanks to the development of various molecular engineering, solution processing, and external alignment methods. These advances have allowed the implementation of organic semiconductors for fabricating high-performance organic electronic devices. In particular, diketopyrrolopyrrole-based small-molecular and polymeric organic semiconductors have garnered considerable research interest due to their ambipolar charge-carrier properties. In this article, we focus on conducting a comprehensive review of previous studies that are dedicated to the external alignment, thermal annealing, and molecular engineering of diketopyrrolopyrrole molecular structures and side-chain structures in order to achieve oriented crystal orientation, optimized thin-film morphology, and enhanced charge carrier transport. By discussing these benchmark studies, this work aims to provide general insights into optimizing other high-mobility, solution-processed organic semiconductors and sheds lights on realizing the acceleration of organic electronic device applications. [ABSTRACT FROM AUTHOR]

Scalable wet high-energy ball milling was used to refine commercial micro-silicon (Si) with water and ethanol as process control agents (PCA). After grinding, the original particle size of 15 microns was reduced to approximately 1 micron for both PCAs. The sample with water as PCA produced more amorphous silicon oxide on the surface of Si particles compared to ethanol, resulting in relatively inferior electrochemical performance. This is attributed to the fact that the water-milling-induced amorphous layer comprises a significant portion of high-valence Si than the ethanol-milling-induced surface layer. Various silicon powders ground with ethanol at different ratios (e.g., 1:3, 1:4, 1:9, and 1:12) were evaluated to establish process–performance relationships. The ball-milled Si powders with a silicon-to-ethanol ratio of 1:9 showed the best electrochemical performance, displaying an initial coulombic efficiency of about 90% and a reversible specific capacity of 3000 mA h/g for the first cycle. After 55 cycles, the reversible specific capacity was maintained at 2200 mA h/g at 0.105 A/g with a corresponding retention rate of 86%, showing good cycling stability. This amorphous shell layer structure introduced through the in situ surface during the grinding process played a role in boosting the electrochemical performance of the micro-silicon anode. In addition, the amorphous shell formed by SiOx on the milled micro-Si surface and its effect on the electrochemical performance are discussed in this paper. [ABSTRACT FROM AUTHOR]

Changes in the interfacial structures of the amorphous silicon (a-Si) anode/organic electrolyte interfaces in lithium-ion batteries were investigated using highly dense a-Si films fabricated by cathodic arc plasma deposition as a model electrode. Raman spectroscopy, transmission electron microscopy (TEM), and X-ray reflectivity revealed that the Si films were grown in an amorphous state with an atomically flat surface. The a-Si films exhibited lithium alloying and de-alloying reactions, with a large irreversible capacity during the first cycle. The irreversible capacity was derived from the formation of a solid electrolyte interphase (SEI) along with an incompletely de-alloyed Li-Si phase, as confirmed by ex situ TEM and X-ray photoelectron spectroscopy observations. The discharge and charge capacities of the Si films gradually decreased in the subsequent cycles, despite the fact that no further SEI formation or cracking of the Si layer occurred. Scanning electron microscopy observations combined with energy-dispersive X-ray spectroscopy revealed the miniaturization of the a-Si film in the surface region to generate domains measuring less than a few hundred nanometers. These results suggest that delamination and miniaturization of the a-Si nanodomains from the electrode surface are partly responsible for degradation of the a-Si anode. [ABSTRACT FROM AUTHOR]

The depth-dependent recovery of silicon thermal conductivity was achieved after the recrystallization of silicon that had been partially amorphized due to ion implantation. Transmission electron microscopy revealed nanoscale amorphous pockets throughout a structurally distorted band of crystalline material. The minimum thermal conductivity of as-implanted composite material was 2.46 W m−1 K−1 and was found to be uniform through the partially amorphized region. X-ray diffraction measurements reveal 60% strain recovery of the crystalline regions after annealing at 450 °C for 30 min and almost full strain recovery and complete recrystallization after annealing at 700 °C for 30 min. In addition to strain recovery, the amorphous band thickness reduced from 240 to 180 nm after the 450 °C step with nanoscale recrystallization within the amorphous band. A novel depth-dependent thermal conductivity measurement technique correlated thermal conductivity with the structural changes, where, upon annealing, the low thermal conductivity region decreases with the distorted layer thickness reduction and the transformed material shows bulk-like thermal conductivity. Full recovery of bulk-like thermal conductivity in silicon was achieved after annealing at 700 °C for 30 min. After the 700 °C anneal, extended defects remain at the implant projected range, but not elsewhere in the layer. Previous results showed that high point-defect density led to reduced thermal conductivity, but here, we show that point defects can either reform into the lattice or evolve into extended defects, such as dislocation loops, and these very localized, low-density defects do not have a significant deleterious impact on thermal conductivity in silicon. [ABSTRACT FROM AUTHOR]

This paper proposes two types of electro-refractive optical modulator structures as a fully CMOS-compatible alternative solution. These modulators leverage the properties of amorphous (top) and crystalline (bottom) silicon films surrounding silicon nitride waveguides operating in the C-band communications range at a wavelength of 1550 nm. Various structures have been demonstrated and explored to compete with or surpass the current state-of-the-art performance of thermal tuners, the most widely used tuning mechanism in silicon nitride integrated photonics. Designs utilizing vertical and lateral p–n junctions with amorphous or crystalline films have been simulated and proposed. For the lateral p–n junctions, modulator lengths to achieve a π phase shift smaller than 287 μm have been demonstrated for the TE mode and that smaller than 1937 μm for the TM mode, reaching 168 μm in the case of a lateral p–n junction that is completely a p-doped region over or under the waveguide for TE, and 1107 μm for TM. Power consumption is higher for the TM modes than for the TE, being in the order of 100 mW for the former and lower than 23 mW for the latter. The modulators exhibit higher losses for amorphous material compared to crystalline, with losses smaller than 10.21 dB and 3.2 dB, respectively. The vertical p–n junctions present a larger footprint than the lateral ones, 5.03 mm for TE and 38.75 mm for TM, with losses lower than 3.16 dB and 3.95 dB, respectively, for the crystalline silicon. Also, their power consumption is on the order of 21 mW for TE and 164 mW for TM. [ABSTRACT FROM AUTHOR]

A room-temperature photoluminescence (PL) study of amorphous Si/amorphous silicon oxynitride multilayer films prepared by plasma-enhanced chemical vapor deposition is reported. The PL peak position can be tuned from 800 nm to 660 nm by adjusting the oxygen/nitride ratio in the a-SiOxNy:H sublayer. The Fourier transform infrared (FTIR) absorption spectra indicate that the shift of the PL peak position is accompanied by an increase in the Si-O-Si absorption peak's intensity, which induces the structural disorder at the interface, resulting in an increase in band gap energy. The effects of size on the photoluminescence spectrum have been studied. As a result, it has been observed that the addition of oxygen atoms introduces a large number of localized states at the interface, causing a blue shift in the emission peak position. With an increase in oxygen atoms, the localized states tend to saturate, and the quantum phenomenon caused by the a-Si sublayer becomes more pronounced. It is found that, as the thickness of the a-Si sublayer decreases, the increase in the [O/N] ratio is more likely to cause an increase in disordered states, leading to a decrease in luminescence intensity. For a-Si/a-SiOxNy:H samples with thinner a-Si sublayers, an appropriate value of [O/N] is required to achieve luminescence enhancement. When the value of [O/N] is one, the enhanced luminescence is obtained. It is also suggested that the PL originates from the radiative recombination in the localized states' T3- level-related negatively charged silicon dangling bond in the band tail of the a-Si:H sublayer embedded in an a-Si/a-SiOxNy:H multilayer structure. [ABSTRACT FROM AUTHOR]

Background: Electronic portal imaging devices (EPIDs) are applied to measure the dose and verify patients' position. Objective: The present study aims to evaluate the performance of EPID for measuring dosimetric parameters in small photon fields. Material and Methods: In this experimental study, the output factors and beam profiles were obtained using the amorphous silicon (a-Si) EPID for square field sizes ranging from 1×1 to 10×10 cm² at energies 6 and 18 mega-voltage (MV). For comparison, the dosimetric parameters were measured with the pinpoint, diode, and Semiflex dosimeters. Additionally, the Monaco treatment planning system was selected to calculate the output factors and beam profiles. Results: There was a significant difference between the output factors measured using the EPID and that measured with the other dosimeters for field sizes lower than 8×8 cm². In the energy of 6 MV, the gamma passing rates (3%/3 mm) between EPID and diode profile were 98%, 98%, 95%, 94%, 93%, and 94% for 1×1, 2×2, 3×3, 4×4, 5×5, and 10×10 cm², respectively. The measured penumbra width with EPID was higher compared to that measured by the diode dosimeter for both energies. Conclusion: The EPID can measure the dosimetric parameters in small photon fields, especially for beam profiles and penumbra measurements. [ABSTRACT FROM AUTHOR]

Three-dimensional magneto-optical traps (3D-MOTs) are an integral component of atomic clocks, quantum computers, and other cold-atom science applications. Due to the dependence on bulk optics and lasers, conventional 3D-MOTs occupy a large volume, limiting their portability. Efforts to build 3D-MOTs using integrated photonics promise to reduce the size and weight of these systems allowing applications beyond the lab. However, the need for counterpropagating beams to facilitate 4- and 6-beam geometries necessitates free-space mirrors and quarter wave plates (QWPs) that limit integration. Replacing these mirrors and QWPs with planar retroreflecting metasurfaces provides a route to achieving a complete 3D-MOT within an integrated package. Here, we report on the design and demonstration of a retroreflecting metasurface for 3D-MOTs that operates at large angles and preserves circular polarization. Specifically, we utilize Bayesian optimization to design an amorphous silicon (a-Si) on gold metasurface for high efficiency polarization-insensitive retroreflection of 780 nm circularly polarized light at 54.7°. Numerical simulations demonstrate maintenance of circular polarization after highly efficient retroreflection ( ϵ − 1 = 1.10 , R − 1 = 0.86). Experimentally, we demonstrate similarly excellent performance at 736 nm at 50.3 ° ( ϵ − 1 = 1.04 , R − 1 = 0.73) and show that deviation from the target design is due to oxidation of the a-Si metaelements. We conclude by discussing mitigation strategies for future devices and propose a corrective optic for the currently fabricated device. This work represents a step toward the miniaturization of 3D-MOTs and expansion of cold-atom science beyond the laboratory. [ABSTRACT FROM AUTHOR]

Hydrosilanes are highly attractive compounds, which can be processed as liquids with printing technology to amorphous silicon films on nearly any solid substrate. The silicon layers can be processed for electronic devices like transistors or thin‐film solar cells. The endothermic character of hydrosilanes with their positive enthalpies of formation results in favorable properties for processing. The larger the molecules, the lower their decomposition temperature and the higher their photoactivity. Cyclic hydrosilanes such as cyclopentasilane and cyclohexasilane can be easily deposited. The branched neopentasilane is more difficult to deposit but yields better‐quality films after processing. The key challenge is the complex synthesis of the precursors and the hydrosilanes. The available preparative methods are presented in this review and their advantages and disadvantages are evaluated. The following synthesis methods are presented and discussed in this article: Wurtz coupling and other reductive coupling processes, dehydrogenative coupling of silanes, plasma synthesis of chlorinated polysilanes, amine‐ or chloride‐induced disproportionations, and transformation of monosilane to higher silanes. Plasma synthesis is already carried out today as a continuous industrial process. The most effective synthesis methods in the laboratory are currently amine‐ and chloride‐induced disproportionations. There is a great need to further optimize the syntheses of hydrosilanes and to develop new simple synthesis variants. [ABSTRACT FROM AUTHOR]

Selenium (Se), the world's oldest optoelectronic material, has been widely applied in various optoelectronic devices such as commercial X‐ray flat‐panel detectors and photovoltaics. However, despite the rare and widely‐dispersed nature of Se element, a sustainable recycling of Se and other valuable materials from spent Se‐based devices has not been developed so far. Here a sustainable strategy is reported that makes use of the significantly higher vapor pressure of volatile Se compared to other functional layers to recycle all of them from end‐of‐life Se‐based devices through a closed‐space evaporation process, utilizing Se photovoltaic devices as a case study. This strategy results in high recycling yields of ≈ 98% for Se and 100% for other functional materials including valuable gold electrodes and glass/FTO/TiO2 substrates. The refabricated photovoltaic devices based on these recycled materials achieve an efficiency of 12.33% under 1000‐lux indoor illumination, comparable to devices fabricated using commercially sourced materials and surpassing the current indoor photovoltaic industry standard of amorphous silicon cells. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous silicon (a-Si:H) has a long history in the development of photovoltaics, especially in the research field of a-Si:H thin-film solar cells and crystalline/amorphous silicon heterojunction solar cells. More than 40 years ago, Staebler and Wronski reported conductance decrease of a-Si:H induced by light soaking. This phenomenon has been widely investigated for electronic applications. In contrast to that, we found light soaking can also improve dark conductance of a-Si:H when boron or phosphorus atoms are doped into the amorphous network. Here we survey these two photoelectronic effects, and discuss their implementations to silicon solar cells. [ABSTRACT FROM AUTHOR]

The purpose of this work is to study the characteristics of the junction between the titanium down conductor of a thin-film solid-state lithium-ion battery (a-Si) and a negative Si@O@Al nanocomposite electrode. The results of measuring the band gap of the Si@O@Al nanocomposite and the height of the Schottky barrier of the Ti–Si@O@Al junction are presented. The transmission and reflection spectra of Si@O@Al films and its main phases a-Si, a-SiOx, and a-Si(Alx) are studied. The band gap of Si@O@Al was determined by the Tauc method, which is 1.52 eV for a-Si and 1.15 eV for nc-Si. The IV characteristics of Ti‒Si@O@Al, Ti–a-Si, Ti–a-SiO0.8, and Ti–a-Si0.9(Al0.1) structures have been studied and the height of the Schottky barrier has been determined. The results obtained make it possible to estimate the Fermi energy of the nanocomposite and to interpret the hike in the SSLIB charging voltage as a result of the Al acceptor impurity compensation during lithiation. A change in the majority charge carriers in Si@O@Al leads to a decrease in the hole current and an increase in the density of the over-barrier electron current, as a result of which a step with a height of 1.5 V is formed on the charging curve. [ABSTRACT FROM AUTHOR]

Active metasurfaces, which are arrays of actively tunable resonant elements, can dynamically control the wavefront of the scattered light at a subwavelength scale. To date, most active metasurfaces that enable dynamic wavefront shaping operate in reflection. On the other hand, active metasurfaces operating in transmission are of considerable interest as they can readily be integrated with chip‐scale light sources, yielding ultra‐compact wavefront shaping devices. Here, designs for all‐dielectric low‐loss active metasurfaces which can dynamically manipulate the transmitted light wavefront in the near‐infrared wavelength range are reported. The active metasurfaces feature an array of amorphous silicon (a‐Si) pillars on a silica (SiO2) substate, which support resonances with quality factors (Q‐factors) as high as 9800. The high‐Q resonance dips observed in transmission can be transformed into transmission resonance peaks by positioning a‐Si pillar resonators at a prescribed distance from a crystalline Si substrate. The design of metasurface geometry with realistic interconnect architectures that enable thermo‐optic dynamic beam switching with switching times as low as 7.3 µs is reported. Beam switching is observed for refractive index differences between neighboring metasurface elements as low as 0.0026. It is shown that the metasurface structures with realistic interconnect architectures can be used for dynamic beam steering. [ABSTRACT FROM AUTHOR]

In this paper, we present the development of a dual‐gate (DG) architecture for hydrogenated amorphous silicon thin film transistors (a‐Si:H TFTs). The aim is to address the challenges of low on‐state current (Ion) and light‐induced degradation in traditional single‐gate (SG) TFTs. The experimental results demonstrate that the DG‐TFT exhibits significantly higher Ion compared to the SG‐TFT, and the improvement depends on the thickness of the top gate insulator. Additionally, the threshold voltage (Vth) can be adjusted by applying the top gate voltage, allowing for a full‐ swing modulation coefficient of approximately 0.2. To ensure long‐term stability, a light‐blocking layer has been incorporated as the top gate electrode, enabling the DG‐ TFT to maintain its initial properties even under intense illumination conditions of up to 28,000 nits. [ABSTRACT FROM AUTHOR]

A photosensitive TFT sensor called bias TFT fabricated using simple amorphous silicon process in this paper. The photosensitive current of bias TFT is linearly related to the brightness of the top light source and inversely proportional to the size of the bias region. The photosensitivity current can be up to 10E‐8 amperes under 100 nits illumination. Among four shapes of bias TFTs, L‐type TFTs have the highest photo current. [ABSTRACT FROM AUTHOR]

A two‐stage output gate driver circuit with a clock‐controlled inverter is proposed and investigated. High and low voltage switching of inverter diminishes the positive bias stress of amorphous silicon TFTs in the circuit. The design of one cell with two‐stage output reduces the number of blocks in the gate driver circuit by half. This circuit was successfully developed for a 27‐inch LCD product with a 1.88 mm border. [ABSTRACT FROM AUTHOR]

The amorphous avalanche photodiodes (a‐Si APD) have been first introduced into flat‐panel detector. The sensor with a‐Si APD indicate much higher sensitivity than normal PIN PD devices. The ultrasensitive image sensor with a‐Si APD can realize optical fingerprint identification under COE OLED screen with very low transmittance. And the flat‐panel X‐ray detector (FPXD) with a‐Si APD can reduce radiation dose significantly because of its much higher sensitivity compared to traditional FPXD products. [ABSTRACT FROM AUTHOR]

Vertical, organic, light‐emitting transistors (VOLETs) combine three of the four essential components of an active matrix lightemitting diode (AMOLED) pixel ‐ the drive transistor, the storage capacitor, and the OLED stack ‐ into a single, highly‐stable, selfemissive structure. VOLETs can be manufactured on amorphous silicon (a‐Si) thin‐film transistor (TFT) backplanes to enable lowcost AMOLED displays with improved brightness and lifetime characteristics. We report on the current status of VOLET development and prospective impact on the active‐matrix display industry. [ABSTRACT FROM AUTHOR]

In spot beam laser annealing, fiber laser and the polygon scanner‐based optical system play a key role by precisely controlling the laser spot position and linear velocities. Key parameters of the laser crystallization are laser power, spot overlap and line overlap. AFM, Raman, and SEM analyzes are used to evaluate polysilicon crystallization state, optimize process parameters, and understand spot beam annealing mechanism. This paper presents the spot beam annealing system configuration and experimental results for low‐temperature poly‐silicon fabrication. [ABSTRACT FROM AUTHOR]

An optical type touch‐input flat panel is designed. The driving system is based on the passive pixel sensor (PPS) array with amorphous silicon (a‐Si) TFT technology. The embedded sensing structure of the optical sensor is using the a‐Si TFT phototransistor and four‐mask process architecture technology. This paper presents a primary optical pixel sensor circuit that utilizes hydrogenated amorphous silicon photo‐transistor sensor. The a‐Si TFT phototransistor sensor is high reliability by using Multi‐N+ layer in the a‐Si TFT structure. [ABSTRACT FROM AUTHOR]

Nanocrystalline silicon oxide (nc-SiOx:H) is a multipurpose material with varied applications in solar cells as a transparent front contact, intermediate reflector, back reflector layer, and even tunnel layer for passivating contacts, owing to the easy tailoring of its optical properties. In this work, we systematically investigate the influence of the gas mixture (SiH4, CO2, PH3, and H2), RF power, and process pressure on the optical, structural, and passivation properties of thin n-type nc-SiOx:H films prepared in an industrial, high-throughput, plasma-enhanced chemical vapor deposition (PECVD) reactor. We provide a detailed description of the n-type nc-SiOx:H material development using various structural and optical characterization techniques (scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Raman spectroscopy, and spectroscopic ellipsometry) with a focus on the relationship between the material properties and the passivation they provide to n-type c-Si wafers characterized by their effective carrier lifetime (τeff). Furthermore, we also outline the parameters to be kept in mind while developing different n-type nc-SiOx:H layers for different solar cell applications. We report a tunable optical gap (1.8–2.3 eV) for our n-type nc-SiOx:H films as well as excellent passivation properties with a τeff of up to 4.1 ms (implied open-circuit voltage (iVoc)~715 mV) before annealing. Oxygen content plays an important role in determining the crystallinity and hence passivation quality of the deposited nanocrystalline silicon oxide films.

The structure of amorphous silicon (a‐Si) is widely thought of as a fourfold‐connected random network, and yet it is defective atoms, with fewer or more than four bonds, that make it particularly interesting. Despite many attempts to explain such "dangling‐bond" and "floating‐bond" defects, respectively, a unified understanding is still missing. Here, we use advanced computational chemistry methods to reveal the complex structural and energetic landscape of defects in a‐Si. We study an ultra‐large‐scale, quantum‐accurate structural model containing a million atoms, and thousands of individual defects, allowing reliable defect‐related statistics to be obtained. We combine structural descriptors and machine‐learned atomic energies to develop a classification of the different types of defects in a‐Si. The results suggest a revision of the established floating‐bond model by showing that fivefold‐bonded atoms in a‐Si exhibit a wide range of local environments–analogous to fivefold centers in coordination chemistry. Furthermore, it is shown that fivefold (but not threefold) coordination defects tend to cluster together. Our study provides new insights into one of the most widely studied amorphous solids, and has general implications for understanding defects in disordered materials beyond silicon alone. [ABSTRACT FROM AUTHOR]

Efficient fiber-chip coupling interfaces are critically important for integrated photonics. Since surface gratings diffract optical signals vertically out of the chip, these couplers can be placed anywhere in the circuit allowing for wafer-scale testing. While state-of-the-art grating couplers have been developed for silicon-on-insulator (SOI) waveguides, the moderate index contrast of silicon nitride (SiN) presents an outstanding challenge for implementing efficient surface grating couplers on this platform. Due to the reduced grating strength, a longer structure is required to radiate the light from the chip which produces a diffracted field that is too wide to couple into the fiber. In this work, we present a novel grating coupler architecture for silicon nitride photonic integrated circuits that utilizes an amorphous silicon (α-Si) overlay. The high refractive index of the α-Si overlay breaks the coupler's vertical symmetry which increases the directionality. We implement subwavelength metamaterial apodization to optimize the overlap of the diffracted field with the optical fiber Gaussian mode profile. Furthermore, the phase of the diffracted beam is engineered to focalize the field into an SMF-28 optical fiber placed 55 µm above the surface of the chip. The coupler was designed using rigorous three-dimensional (3D) finite-difference time-domain (FDTD) simulations supported by genetic algorithm optimization. Our grating coupler has a footprint of 26.8 × 32.7 µm2 and operates in the O-band centered at 1.31 μm. It achieves a high directionality of 85% and a field overlap of 90% with a target fiber mode size of 9.2 µm at the focal plane. Our simulations predict a peak coupling efficiency of − 1.3 dB with a 1-dB bandwidth of 31 nm. The α-Si/SiN grating architecture presented in this work enables the development of compact and efficient optical interfaces for SiN integrated photonics circuits with applications including optical communications, sensing, and quantum photonics. [ABSTRACT FROM AUTHOR]

Pure silicon oxide was produced in this study utilizing a sodium silicate solution made from Kankara clay as a precursor. The Kankara clay that was obtained from Nigeria was first beneficiated to produce pure dried powder clay. After that, the dried powdered clay was treated with heat activation and acid leaching, respectively. In a 500 mL Erlenmeyer flask, appropriate amounts of each clay (raw, thermally treated clay, and leached clay) were reacted with 3M NaOH solution. The flask was heated to 200°C and stirred continuously for 3 hours on a magnetic stirring hot plate connected to a reflux condenser. The solution was filtered to yield sodium silicate solution, which was then precipitated with 3M HCl while constantly stirring to produce a gelly-like white substance. The gel was aged for 18 hours, then washed with de-ionized water several times before being dried at 80°C for 12 hours to get pure white silica particles, which were subsequently described. The XRD analysis revealed that the silicon oxide synthesized is amorphous, but the microstructure evaluation revealed particles aggregation, which is usual in sol-gel synthesized powder. [ABSTRACT FROM AUTHOR]

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The nature of structural changes of nanosecond laser modification inside silicon is investigated. Raman spectroscopy and transmission electron microscopy measurements of cross sections of the modified channels reveal highly localized crystal deformation. Raman spectroscopy measurements prove the existence of amorphous silicon inside nanosecond laser induced modifications, and the percentage of amorphous silicon is calculated based on the Raman spectrum. For the first time, the high-resolution transmission electron microscopy images directly show the appearance of amorphous silicon inside nanosecond laser induced modifications, which corroborates the indirect measurements from Raman spectroscopy. The laser modified channel consists of a small amount of amorphous silicon embedded in a disturbed crystal structure accompanied by strain. This finding may explain the origin of the positive refractive index change associated with the written channels that may serve as optical waveguides. [ABSTRACT FROM AUTHOR]

Silicon nitride (Si3N4) is an ideal candidate for the development of low-loss photonic integrated circuits. However, efficient light coupling between standard optical fibers and Si3N4 chips remains a significant challenge. For vertical grating couplers, the lower index contrast yields a weak grating strength, which translates to long diffractive structures, limiting the coupling performance. In response to the rise of hybrid photonic platforms, the adoption of multi-layer grating arrangements has emerged as a promising strategy to enhance the performance of Si3N4 couplers. In this work, we present the design of high-efficiency surface grating couplers for the Si3N4 platform with an amorphous silicon (α-Si) overlay. The surface grating, fully formed in an α-Si waveguide layer, utilizes subwavelength grating (SWG)-engineered metamaterials, enabling simple realization through single-step patterning. This not only provides an extra degree of freedom for controlling the fiber–chip coupling but also facilitates portability to existing foundry fabrication processes. Using rigorous three-dimensional (3D) finite-difference time-domain (FDTD) simulations, a metamaterial-engineered grating coupler is designed with a coupling efficiency of −1.7 dB at an operating wavelength of 1.31 µm, with a 1 dB bandwidth of 31 nm. Our proposed design presents a novel approach to developing high-efficiency fiber–chip interfaces for the silicon nitride integration platform for a wide range of applications, including datacom and quantum photonics. [ABSTRACT FROM AUTHOR]

Micro-structured silicon surface plays a significant role in the electronics industry. Crystalline and amorphous phases of silicon, which have significantly different physical properties, can be transformed into each other using femtosecond laser, and assisted chemical etching enables the easy fabrication of various micro-structures. However, efficient and controllable fabrication of micro-cylinders, micro-rings, and micro-ring grooves on silicon surfaces still remains a challenge. Here, we propose a temporally modulated single-shot femtosecond pulse lithography technology, combining laser-induced silicon modification and chemical etching. In this technology, the occurrence of recrystallization allows for the flexible manipulation of the shape of the modified area, transitioning from circular to annular shapes by adjusting the laser fluence. This corresponds to the formation of micro-cylinders and micro-rings after etching. In the case of temporally shaped pulses, with an increasing pulse delay, the micro-rings formed after etching gradually transform into micro-ring grooves, as the recrystallization area created by the first sub-pulse is reacted by the second sub-pulse. Due to the characteristics of the single shot, the technology, when combined with the flying punch method, can be used for the high-efficiency fabrication of large-area silicon surface micro-structure arrays. [ABSTRACT FROM AUTHOR]

Photonic routing holds immense significance in the fields of photonic integrated circuits (PICs) for free‐space optical linking. The emergence of programmable metasurfaces with powerful phase regulation capability provides a promising strategy for achieving designated wavefront modulation and thus photonic routing in the optical communication waveband. Here, a bilayer metasurfaces with four‐level codable unit pixels, which realize controllable photonic routing in near‐infrared (NIR) region is reported. The unit pixel of the metasurfaces consists of the underneath amorphous silicon (α‐Si) nanofin and the upper Ge2Sb2Te5 (GST) nano‐antenna, which contribute to the cross‐polarization generation and amplitude modulation of cross‐polarization light, respectively. Each unit pixel can be designated with desired states, thus achieving on‐demand non‐volatile photonic routing for coherent NIR light. In particular, polarization conversion modulation of the tunable metasurfaces comprising identical unit cell with large cross‐polarization switching (≈55%) at ≈1550 nm is demonstrated. Moreover, the metasurfaces with coded unit pixels to realize designated photonic routing are prototyped. The metasurfaces with four‐level programmability portend a new paradigm in NIR photonic routing for PICs. [ABSTRACT FROM AUTHOR]

This work addresses the design and verification of an outdoor 55‐inch 4K‐resolution and high‐brightness liquid crystal display (LCD) product. The new pixel design is able to increase the module transmittance to as high as 6.24%. The amorphous silicon (a‐Si) thin film transistor (TFT) has excellent light‐ and temperature‐stability. The gate drive circuit has been improved to reduce the operating temperature by 5~7 ℃. The brightness of the display is up to 4056 nits, which is the brightest known 55‐inch 4K‐resolution display product. [ABSTRACT FROM AUTHOR]

The threshold voltage behavior of TFTs is an important indicator of device stability. In this paper, the effects of silicon nitride content, film thickness, and structure of the gate insulating layer of amorphous silicon TFTs on device stability are investigated. The study reproduces the abnormal turnaround phenomenon of amorphous silicon TFT threshold voltage. We optimized the device conditions with high stability. Applying the optimized device conditions, we developed a 55‐inch 4K resolution LCD product with a brightness of 4000nits. Its performance is excellent in 3000hrs accelerated aging test. [ABSTRACT FROM AUTHOR]

In this work, the stability of hydrogenated amorphous silicon (a‐Si:H) thin‐film transistors (TFTs) under reliability (RA) test was studied and a two‐stage degradation behavior during the RA test was first observed. The influence of bandgap (Eg) of the SiNx gate insulator (GI) on the degradation behavior was studied and the SiNx GI of a high Eg was found of vital importance due to its better blocking capability against electron injection from gate electrode into GI. The results in this work indicated technological impact for a‐Si:H TFTs in high‐brightness LCD products for outdoor display applications. [ABSTRACT FROM AUTHOR]

The surface passivation quality of intrinsic hydrogenated amorphous silicon (i‐a‐Si:H) layers deposited by constant DC power‐facing target sputtering (FTS) technology is investigated. An n‐type crystalline silicon wafer passivated with a 42 nm‐thick i‐a‐Si:H shows an effective carrier lifetime of 11 ms, which corresponds to a low upper limit effective surface recombination velocity Seff of 1.27 cm s−1. An ultrathin 5 nm‐thick i‐a‐Si:H film achieves an implied open‐circuit voltage (iVoc) of 730 mV at a high deposition rate of 31 nm min−1. It is found that constant DC‐FTS does not cause sputtering damage under high deposition rate conditions. This work demonstrates that i‐a‐Si:H deposited by constant DC‐FTS can achieve the same passivation quality as i‐a‐Si:H deposited by plasma‐enhanced chemical vapor deposition or catalytic chemical vapor deposition, paving the way for the fabrication of silicon heterojunction solar cells without the use of explosive and toxic gases. [ABSTRACT FROM AUTHOR]

We present a detailed analysis based on both experimental and 3D modelling approaches of the unique silicon nitride precipitation sequence observed in ferritic Fe-Si alloys upon nitriding. At 570 °C, Si3N4 silicon nitride was shown to form as an amorphous phase into α-Fe ferrite matrix, which is morphologically unstable over time. Precipitates nucleated with a spheroidal shape, then developed a cuboidal shape for intermediate sizes and octapod-like morphology for a longer time. Using transmission electron microscopy, we show that the transition between spheroid and cuboid morphology depended on particle size and resulted from competition between interfacial energy and elastic strain energy. The resulting morphology was then shown to be a cuboid shape whose faces were always parallel to the {100} planes of the α-Fe; the <100> directions of the matrix corresponded to the elastically soft directions. There was a critical size of around 45 nm for which the transition between the cuboid shape and the octapod-like morphology took place. This was characterised by a transformation of quasi-flat facets into concave ones and the development of lobes in the <111> directions of the bcc crystal. To better assess the kinetic effects of diffusion fields and internal stresses on the morphological instability observed, an original 3D model that explicitly coupled phase transformations and mechanical fields was developed and applied. The latter, validated on the basis of model cases, was shown to be able to describe the time-evolution of both chemical and mechanical fields and their interactions in diffusive mass transport. Using a model system, it was shown that the concentration field around the precipitates and the internal stresses played opposing roles in the cuboid to octapod-like morphological instability. This work gives some clarification regarding the morphological evolution of amorphous Si3N4 precipitates, an important point for controlling the mechanical properties of nitrogen steels. [ABSTRACT FROM AUTHOR]